tag:blogger.com,1999:blog-71319574403810980472024-03-14T06:44:26.845+01:00Øyvind KvålsvollArticles on audio, sound, design. <br><br>
Visit Kvålsvoll Design at <a href="http://www.kvalsvoll.com">www.kvalsvoll.com</a>Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.comBlogger21125tag:blogger.com,1999:blog-7131957440381098047.post-285005690066393002017-12-15T03:09:00.004+01:002017-12-15T03:09:48.694+01:00Moving to new locationThis blog continues on the Kvålsvoll Design site:<br />
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<a href="https://www.kvalsvoll.com/blog/en/">https://www.kvalsvoll.com/blog/en/</a>Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-16378642499870141922016-09-06T15:28:00.001+02:002016-09-06T15:28:43.291+02:00Acoustic absorber building description<a href="http://1.bp.blogspot.com/-lvhyEFLDams/VhqTVEWCjhI/AAAAAAAAAUE/2sTFWG3szwM/s1600/logo07.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br /></a>
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<h2>
Acoustic absorber building description</h2>
Several acoustic absorbers with different shape and size were made for the new Room 2 listening room. <br />
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Building description with construction drawings:<br />
<a href="http://www.kvalsvoll.com/Designs/absorber120x120x20/absorber120x120x20_buildingdescription_en.pdf">www.kvalsvoll.com/Designs/absorber120x120x20/absorber120x120x20_buildingdescription_en.pdf</a><br />
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Presentation:<br />
<a href="http://www.kvalsvoll.com/Designs/absorber120x120x20.htm">www.kvalsvoll.com/Designs/absorber120x120x20.htm</a><br />
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<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-4974407957125730292015-11-24T07:15:00.001+01:002015-11-24T07:25:13.162+01:00Why Vinyl Sounds Better<a href="http://1.bp.blogspot.com/-lvhyEFLDams/VhqTVEWCjhI/AAAAAAAAAUE/2sTFWG3szwM/s1600/logo07.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br /></a>
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Vinyl sounds better, right? If so, there is a reason that can be explained in technical terms. Let us find out. </span></b></i></span><br />
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<span style="font-size: large;"><i><b><span style="color: #999999;">The answer is simply that vinyl does not sound better, in fact it is inferior to digital. </span></b></i></span><br />
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<h2>
Why vinyl sounds better</h2>
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Today was a good time to find out why vinyl <span class="" id="result_box" lang="en"><span class="hps atn">(</span>what we called <span class="hps">turntable</span> and records <span class="hps">in the old</span> times<span class="hps"></span>) <span class="hps">sounds better</span>.</span><span class="" id="result_box" lang="en"> </span><br />
<span class="" id="result_box" lang="en"><span class="hps">So</span> <span class="hps">the plan is to</span> <span class="hps">rip</span> <span class="hps">some records</span> <span class="hps">I have,</span> <span class="hps">some of which are not </span><span class="hps">available on</span> <span class="hps">digital.</span></span><br />
<span class="" id="result_box" lang="en">There are some good stuff here that may make its way to the demo list as well. </span><br />
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<h3>
<span class="" id="result_box" lang="en"></span>The preamplifier<span class="" id="result_box" lang="en"><span class="hps"> </span></span></h3>
<span class="" id="result_box" lang="en"><span class="hps">Central to</span> <span class="hps">this exercise</span> <span class="hps">is</span> <span class="hps">this</span> <span class="hps">preamplifier</span>, <span class="hps">it</span> <span class="hps">is</span> <span class="hps">the last one I</span> <span class="hps">made</span> <span class="hps">in late </span><span class="hps">80's.</span> </span><br />
<span class="" id="result_box" lang="en"><br /><span class="hps">It has</span> <span class="hps">MC</span> <span class="hps">input</span> only, for <span class="hps">pickups</span> like <span class="hps">MC30</span> <span class="hps">and</span> <span class="hps">AT</span> <span class="hps">OC9</span>.<br /><span class="hps">It had</span> a <span class="hps">shunt-regulator</span> <span class="hps">power supply burning </span><span class="hps">continuous</span> <span class="hps">power</span> <span class="hps">as</span> <span class="hps">a medium</span> <span class="hps">power amplifier</span> <span class="hps">long before this</span> <span class="hps">became a</span> trend <span class="hps">in the</span> <span class="hps">audio</span> <span class="hps">world.</span><br /><span class="hps"> </span></span><br />
<span class="" id="result_box" lang="en"><span class="hps">The problem</span> <span class="hps">with</span> <span class="hps">preamps</span> <span class="hps">for</span> <span class="hps">MC</span> <span class="hps">is</span> <span class="hps">noise</span> <span class="hps">and</span> <span class="hps">low-level</span> <span class="hps">distortion</span>, <span class="hps">because the signal</span> <span class="hps">is so low that</span> <span class="hps">the thermal</span> <span class="hps">noise of</span> the source generator impedance <span class="hps">becomes</span> <span class="hps">significant.</span><br /><span class="hps">The best</span> <span class="hps">one can achieve</span> <span class="hps">is to</span> <span class="hps">get as close to</span> <span class="hps">this</span> <span class="hps">physical</span>ly <span class="hps">given</span> <span class="hps">constraint</span> <span class="hps">as possible.</span><br /><span class="hps">FET</span> <span class="hps">transistors</span> <span class="hps">that have long</span> <span class="hps">been</span> out of production and now <span class="hps">impossible to find</span> <span class="hps">solves</span> <span class="hps">this problem</span>, providing <span class="hps">extreme clarity and resolution </span>but at the same time <span class="hps"></span> <span class="hps">comfortable</span>, <span class="hps">easy-to-listen-to</span> <span class="hps">sound.</span></span><br />
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<i>The preamplifier for moving coil pick-up</i><br />
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I was never satisfied with any of the front plates I made, so it usually ended up without.<br />
The volume knob is massive brass, it weighs so much it destroys the potentiometer, and that is how it is supposed to be.<br />
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Is it better<span class="" id="result_box" lang="en"><span class="hps"> </span></span></h3>
<span class="" id="result_box" lang="en"><span class="hps">First part is to </span><span class="hps">find a suitable</span> vinyl record <span class="hps">which I also</span> <span class="hps">have</span> <span class="hps">in</span> <span class="hps">digital format</span>, where it is likely <span class="hps">that the</span> <span class="hps">master</span> <span class="hps">is</span><span class="hps"> similar</span>.<span class="hps"> So that the</span><span class="hps"> mythical vinyl sound can be compared to the </span><span class="hps">digital version</span>, <span class="hps">and</span> <span class="hps">hear</span> <span class="hps">what is better</span> <span class="hps">on</span> <span class="hps">vinyl</span>.</span> <br />
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<span class="" id="result_box" lang="en"><span class="hps">Well,</span> <span class="hps">it</span> turn<span class="hps">s out that</span> <span class="hps">it</span> <span class="hps">really</span> does not sound <span class="hps">much</span> <span class="hps">better</span>. </span><br />
<span class="" id="result_box" lang="en"><span class="hps">The differences</span> <span class="hps">can be attributed to</span> <span class="hps">differences in</span> <span class="hps">frequency response</span>, <span class="hps">with</span> <span class="hps">eq</span> <span class="hps">in</span> <span class="hps">one or the other</span> <span class="hps">it sounds</span> <span class="hps">pretty similar.</span></span><br />
<span class="" id="result_box" lang="en">P<span class="hps">art from</span> <span class="hps">a few things that</span> <span class="hps">are</span> <span class="hps">significantly worse</span> <span class="hps">on</span> <span class="hps">vinyl</span>. </span><br />
<span class="" id="result_box" lang="en"> <span class="hps">The noise level is</span> <span class="hps">so high</span> <span class="hps">that the</span> <span class="hps">decay</span> <span class="hps">and room information</span> <span class="hps">are</span> <span class="hps">somewhat</span> <span class="hps">masked, the</span> <span class="hps">scene is </span><span class="hps">a bit smaller and</span> <span class="hps">narrower</span>, <span class="hps">the bass</span> <span class="hps">is more powerful</span> <span class="hps">and</span> <span class="hps">less precise</span>, higher frequencies <span class="hps">less sharp</span> <span class="hps">and more</span> <span class="hps">flat.</span></span><br />
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No, it is definitely not necessary to do a blind test to verify that there is a difference.. <br />
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On some albums the vinyl may sound better overall because the noise masks quite a lot, and added distortion can give more "musicality".<br />
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<h3>
Technical analysis</h3>
Comparing vinyl to digital reveals there is no significant difference in dynamics:<br />
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Vinyl is the first graph. <br />
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The allpassed crest is flat for both, and the small difference can be attributed to differences in spectral balance, the vinyl is tilted towards more bass and less highs: <br />
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As usual, this corresponds well with listening impressions. <br />
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But what with the claims for higher measured dynamics for vinyl?<br />
In some cases the reason is different masters, and additional difference in measured crest is due to use of limiters, which causes crest to increase when played back on vinyl due to phase changes. <br />
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<h3>
Advantages from ripping vinyl to digital</h3>
Using a reference-quality AD-converter and computer it is possible to do digital recordings of the vinyl records, with no loss of sound quality, the resulting digital files will sound exactly like the sound coming from the exotic preamplifier.<br />
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Convenience - can be played back just like all the other music, is one obvious advantage. <br />
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But the sound will also be better.<br />
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It is now possible to fix faults introduced in the vinyl playback process, with digital signal processing on the sound files.<br />
Improper channel balance, faults in frequency response, can be fixed.<br />
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Pop and cracks can be removed - a very audible improvement.<br />
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In my system there is digital signal processing for crossover and bass management, requiring any analog input to be converted to digital. Potentially, this additional conversion can affect sound quality - may be it doesn't, but now that the source is digital like everything else, this problem is eliminated. <br />
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And yes, the ripped digital files sounds exactly like the original vinyl. And will continue to do so, without loss of quality due to vinyl wear. <br />
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<h3>
Vinyl sound is just another audio myth</h3>
So, this was not a step in the right direction towards audio nirvana. <br />
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A record player also means a lot of nuisance.<br />
It has to be leveled, adjustments and alignments for the pick-up, dust removal.<br />
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<span class="" id="result_box" lang="en"><span class="hps">Yesterday</span> <span class="hps">I listened to an Opus3 recording, the one with the track "Tiden bara går". </span></span><br />
<span class="" id="result_box" lang="en"><span class="hps">Fantastic</span>, <span class="hps">with</span> <span class="hps">Therese</span> <span class="hps">Juel</span> <span class="hps">visiting</span> <span class="hps">in my room,</span> <span class="hps">exactly as I</span> <span class="hps">remember it from</span> <span class="hps">the old</span> <span class="hps">days. </span></span><br />
<span class="" id="result_box" lang="en"><span class="hps">I downloaded</span> <span class="hps">a</span><span class="hps">n</span> <span class="hps">mp3</span> <span class="hps">of this</span> <span class="hps">track</span> <span class="hps">recently (it is provided as a free sample) and</span> <span class="hps">it does not sound like this at all</span><span class="hps">, this is one reason I was tempted to set up the turntable again, to see if that magic from the old day was still there.</span></span><br />
<span class="" id="result_box" lang="en"><br /><span class="hps">But</span> <span class="hps">when</span> <span class="hps">comparing even good quality vinyl records to decent digital, digital is preferable. </span></span><br />
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I will rip a few records, then the exotic preamplifier and the record player is going back to where they belong - as a show-off in a storage room. <br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com1tag:blogger.com,1999:blog-7131957440381098047.post-68266670881346653082015-10-11T19:04:00.001+02:002015-10-11T19:10:55.970+02:00About the author<a href="http://1.bp.blogspot.com/-lvhyEFLDams/VhqTVEWCjhI/AAAAAAAAAUE/2sTFWG3szwM/s1600/logo07.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><br /></a>
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<span style="font-size: large;"><i><b><span style="color: #999999;">
I have now presented short technical articles on sound here, for some time. Who am I, what is my background, what is my intention.
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About the author</h2>
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Intention</h3>
I want to increase interest for sound and sound quality. <br />I like good sound, and want to contribute to increased awareness and focus on sound and what it adds to the experience of music and movies. <br /><br />Presenting facts and informative articles is one of the ways I have chosen to contribute.<br />
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<h3>
Current status of the blog</h3>
This blog presents articles with a very specialized and narrow perspective - effort, knowledge and interest in sound is required to understand and benefit from the content. <br /><br />So this is for the experts, for those with a special interest for sound related technology. <br />That narrows the potential audience down to a small group of people. <br /><br />After running this blog for two years, the audience is still very small, and that is the main reason for the rather low frequency of updates, there is not much point in writing if there are no readers. <br /><br />I recommend my <a href="http://www.kvalsvoll.com/index.htm">company web pages</a> for more articles and information on what I am developing. <br /><br /><h3>
About the author</h3>
This text is taken from the article <a href="http://www.kvalsvoll.com/Articles/HowtosetupaHomeTheaterSoundSystem.htm">How to set up a Home Theater Sound System</a> on the Kvålsvoll Design company web page: <br /><br /><br />I run the Norwegian registered company Kvålsvoll Design AS.<br /><br />I like to create things, I like to work on engineering challenges as well as shape and visual appearance. I also enjoy working on abstractions like systems and concepts. This forms the foundation of Kvålsvoll Design.<br /><br />I am an engineer in cybernetics and electronics. I have started several companies, and I have designed, built and tested complex cybernetic systems involving advanced dynamic control algorithms.<br /><br />I designed and built my first speakers around age 14, and continued exploring and building audio speakers and amplifiers as a hobby throughout the years, learning more and applying what I learned in school about electronics, system theory and mathematics.<br /><br />In 2012-2013 I started designing loudspeaker systems for home entertainment. Development is based on my expertise on simulation and dynamic systems. I have also learned a lot about how we perceive sound, which is of vital importance for defining proper requirements for sound system design.<br /><br />The development of audio solutions in Kvålsvoll Design has lead to several new technologies for sound reproduction, such as the Compact Horn subwoofers, controlled directivity waveguide horns, very-high-slope crossover networks.<br /><br />Acknowledging the importance of set-up and calibration, a new method for subwoofer calibration has been developed, which accounts for sound-field intensity for better tactile feel. This is new, and Kvålsvoll Design is so far the only company using this method.<br /><br /><br /><br />Thank you for reading,<br /><br />Øyvind Kvålsvoll<br /><br /><a href="http://1.bp.blogspot.com/-lvhyEFLDams/VhqTVEWCjhI/AAAAAAAAAUE/2sTFWG3szwM/s1600/logo07.png" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-lvhyEFLDams/VhqTVEWCjhI/AAAAAAAAAUE/2sTFWG3szwM/s1600/logo07.png" /></a>Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-80244451354445098562015-07-12T05:02:00.004+02:002015-07-13T01:48:02.045+02:00Audio in 2015 - a summary of trends<a href="http://kvalsvollnorsk.blogspot.no/2015/07/lyd-i-2015-en-oppsummering-av-trender.html">Norsk versjon / Norwegian version -></a>
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<span style="font-size: large;"><i><b><span style="color: #999999;">
This is meant as an update on audio for those who have been out of the game for a while. <br /><br />
Some technology improvements, but most of all the wide-spread communication on internet, has made it possible to get huge improvements in sound quality.
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The new sound</h2>
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1. Dynamics and realism with high efficiency speakers</h3>
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It's the new sound trend - dynamics, realism, more life-like. <br />
Speakers with higher efficiency, more output capacity and controlled sound radiation pattern is the key. <br />
Often larger, with horns, often utilise professional loudspeaker drivers. <br />
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Dome tweeters and small satellites with small woofers are out - large woofers, horns and waveguides are in. <br />
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<i>Big is back and small is now old-school</i><br />
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<h3>
2. Acoustics </h3>
<br />
We always knew the room and furniture in it, along with placement of loudspeakers and listening position, have a significant effect on sound quality. <br />
What is new is an overall awareness and knowledge on acoustics, we no longer accept a bad room as something inevitable, we actually do something about it to fix the problem. <br />
<br />
<i>Acoustic absorbers on the rear wall next to the S1.2 rear surround speaker </i><br />
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<a href="http://3.bp.blogspot.com/-rC5I6uMFjKo/VaHQ3p6GZTI/AAAAAAAAATY/JpqaawdqzbM/s1600/P1040681.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="400" src="http://3.bp.blogspot.com/-rC5I6uMFjKo/VaHQ3p6GZTI/AAAAAAAAATY/JpqaawdqzbM/s400/P1040681.jpg" width="300" /></a></div>
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<br />
<h3>
</h3>
<h3>
3. Measurement capability </h3>
<br />
Today any amateur hobbyist can set up a rig for acoustic measurements on the speakers and room using very little money, and the performance will be equal to or in many ways much better than what you would have paid an amount similar to a new car to get in the good old days.<br />
<br />
You need a portable pc - which you already got, microphone, I/O interface for the pc, and the free software measurement package REW. <br />
<br />
This will allow you to actually see what is going on when you try to set up your system, save you a lot of time - if better sound is the goal, and probably kill some myths. <br />
<br />
When you now are able to measure, you can go on with acoustic improvements and integrate you new high-efficiency speakers that rolls off everything below 60Hz to your new bass system. <br />
Just being able to integrate the bass with the main speakers so that it doesn't sound like the typical speakers-with-subwoofer will be a very significant improvement. <br />
<br />
<br />
<i>PC laptop computer with REW measurement software running</i><br />
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<a href="http://1.bp.blogspot.com/-jTAwbfkocYw/VaHGqWRUeVI/AAAAAAAAASU/K3xUBT978V8/s1600/P1040238.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="300" src="http://1.bp.blogspot.com/-jTAwbfkocYw/VaHGqWRUeVI/AAAAAAAAASU/K3xUBT978V8/s400/P1040238.jpg" width="400" /></a></div>
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<br />
<h3>
</h3>
<i>Microphone on stand measuring the S1.2 surround speaker </i><br />
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<a href="http://1.bp.blogspot.com/-qspEMw1VX7U/VaHIBYOgl2I/AAAAAAAAASo/dFc0245NOfg/s1600/P1030405.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="300" src="http://1.bp.blogspot.com/-qspEMw1VX7U/VaHIBYOgl2I/AAAAAAAAASo/dFc0245NOfg/s400/P1030405.jpg" width="400" /></a></div>
<br />
<br />
<h3>
4. Bass systems</h3>
<br />
Huge bass systems pop up everywhere. <br />
Large horns, or multiple subwoofer units with large-displacement drivers, or dipole variations. <br />
<br />
This is a difference that is very audible, very visible - they are large, and physically perceptible. <br />
The home-theaters showed the way with large-capacity subwoofer systems with low frequency extension well below 20Hz. <br />
<br />
Today, any serious audio system has a capable and properly integrated bass system. <br />
<br />
<br />
<h3>
5. Scams busted </h3>
<br />
In the 90's a trend towards seeing audio as something more spiritual and supernatural really took off. <br />
Established science and methodology were replaced by occultism and religion. <br />
This was boosted by scam manufacturers appearing on the market with expensive cables and all sorts of products claimed to improve sound but having no technical foundation at all. <br />
<br />
They are all busted. <br />
<br />
Yes, the manufacturers still live on, they continue to spread their religion - often supported by a cult of believers, but today anyone can search around the internet and find information on those subjects and find the truth. <br />
We know why the scam marketers continue to spread the word, we know why people hear differences that does not really exist, and there is scientific documentation on technical issues and listening tests. <br />
<br />
If you encounter a salesman telling you a more expensive piece of wire will sound better, then it's either a scam, or the salesman is incompetent. <br />
I would not deal with either. <br />
<br />
<br />
<h3>
6. Audibly transparent</h3>
<br />
It is apparent for anyone with a technical background that a piece of wire can not change the sound the way some people claim to hear. <br />
This led to a better understanding of the concept expectation bias - what you see affects what you think you hear. <br />
The next logical step then is to question whether other parts of the audio chain, like amplifiers, could also be so good, that they do not change the sound in any way that can be audibly perceptible. <br />
<br />
This gives birth to the term "audibly transparent" - a device that is so good that it does not change the signal in any way that is audible. <br />
<br />
Blind listening tests, often performed as what is called an ABX-test, show that indeed, the audible differences between CD-players, amplifiers, DA-converters are not anything like what you can read in the hifi-magazine reviews. <br />
In fact, those controlled listening tests show that well constructed high-quality equipment does not change the audio signal in any way that is audible. <br />
<br />
Today it is easy to establish whether a device is audibly transparent. <br />
You measure it. <br />
When all changes made to the original signal is well below threshold of hearing, it is audibly transparent. <br />
<br />
Basically, everything up to the speaker terminals can be made audibly transparent. <br />
<br />
Take a look back at the <a href="http://kvalsvoll.blogspot.no/2015/03/testing-amplifier-sound-quality.html">amplifier sound quality article</a> - the test samples are still available. <br />
Can you hear a difference between the power amplifiers tested? <br />
Can you hear a difference between the original music sample and the one passed through the AV-receiver 4 - FOUR - times?<br />
<br />
A consequence of the fact that one can actually use a AV-receiver in the signal chain and be sure that it is completely audibly transparent is better sound for less money. <br />
Less money because they are mass produced and targeted at a slightly different market, and better because you now have signal processing capabilities like bass management and delay setting for all speakers so the subwoofer can be properly integrated. <br />
<br />
But be very aware that this does not mean there are no differences in functionality or performance - output power of amplifiers must be properly dimensioned, and differences in functionality can make one device more suitable than the other. <br />
<br />
<br />
<h3>
..</h3>
<br />
In addition to the mentioned points, there is the difference in how we receive and play source media content. <br />
Streaming from internet, pc-playback and the removal of physical media like the CD. <br />
In this world the old vinyl records have their renaissance, and is now known as - vinyl. <br />
<br />
<br />
<br />
<br />
<i>Computer playback of music files. Kodi media player. </i> <br />
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<a href="http://4.bp.blogspot.com/-H0VG7OS7JQo/VaHExuLHyyI/AAAAAAAAASA/5bth8E1hm5k/s1600/nublado.jpg" imageanchor="1" style="clear: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="257" src="http://4.bp.blogspot.com/-H0VG7OS7JQo/VaHExuLHyyI/AAAAAAAAASA/5bth8E1hm5k/s400/nublado.jpg" width="400" /></a></div>
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<a href="http://4.bp.blogspot.com/-KSvd7NzE2aE/VaHE0_PE_zI/AAAAAAAAASI/kIa2d8pR4bQ/s1600/brassbandistua_1.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div>
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<br />
<br />
If you are in Norway, you can visit the <a href="http://www.kvalsvoll.com/contact.htm">Kvålsvoll Design AS</a> demo room to experience some of those new trends in sound. <br />
You are welcome. Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-90375035011866251772015-03-14T02:46:00.000+01:002015-03-23T17:22:19.439+01:00Testing Amplifier Sound Quality <br />
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<a href="http://3.bp.blogspot.com/-xHmSh6q-ceA/VQOHklBI8tI/AAAAAAAAARc/g5hipsNO1xA/s1600/intro.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-xHmSh6q-ceA/VQOHklBI8tI/AAAAAAAAARc/g5hipsNO1xA/s1600/intro.jpg" height="318" width="640" /></a></div>
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<br />
<span style="font-size: large;"><i><b><span style="color: #999999;">This is something I have though about a long time now - finding a method to reliably verify sound quality differences in power amplifiers.<br /><br />Finally I have set up the necessary instrumentation to try out the method in practical experiments.</span></b></i></span><br />
<br />
<br />
<br />
<h3>
</h3>
<h3>
<b>Purpose </b></h3>
Today good sound is easy to achieve, most of the audio playback chain can be made sonically transparent with relatively little effort and money spent. <br />
<br />
However, through building and designing amplifiers myself, and measuring and listening to many different amplifiers, I have got this controversial idea that power amplifiers can actually sound different.<br />
<br />
Obviously they sound different if you push beyond power limits, and also amplifiers can be made so good that they are transparent for any source material.<br />
<br />
But where is the limit, how good does it have to be, and what measurements can reveal the transparent ones from the only-good ones.<br />
<br />
<br />
<h3>
Method</h3>
The problem with listening tests for verification is that it is time consuming, unreliable and difficult to do proper blind testing of amplifiers.<br />
<br />
If you could test using a software abx-tester, like the one in foobar, the task would become easier.<br />
<br />
By recording the output signal from the amplifier while playing at decent volume, you get a sample file that can be compared to the original in an abx software player, and you can do the comparison on any playback system - headphones, speakers.<br />
<br />
The playback will of course be affected by the amplifier in use for playback, but considering descriptions of the seemingly huge sonic differences described in reviews, it should not be a problem to hear at least some of the sound characteristics from the test object. <br />
<br />
<br />
<i>Method for amplifier abx-testing; The blue boxes are sound data files, the green boxes are test instrumentation and should sound transparent, the red box is the amplifier being tested: </i><br />
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<a href="http://4.bp.blogspot.com/-LeuaOIVD5YQ/VQOIUgPbLCI/AAAAAAAAARk/AD9lLP7ovdo/s1600/abx.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-LeuaOIVD5YQ/VQOIUgPbLCI/AAAAAAAAARk/AD9lLP7ovdo/s1600/abx.png" height="480" width="640" /></a></div>
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<br />
<h3>
Verifying the recorder</h3>
After rigging the recording system, the first task is to verify that the recorder is sonically transparent, or at least much better than the amplifiers I want to test.<br />
<br />
The first recorder system is made easy and practical, thought I could test this first, if it fails I have some options to improve it if necessary.<br />
<br />
I recorded some samples from the output going to the amplifier, so that I can use abx to verify if there is an audible difference from the original sample to the recorded sample - with no amplifier in the loop.<br />
<br />
I also took one of the samples and sent it through this loop 5 times, as I suspected the differences would be too small to be detected.<br />
<br />
If the 5x loop sample still sounds good, then the recorder can be assumed to be good enough for the purpose.<br />
<br />
After several attempts trying to get an abx with positive outcome, I conclude I am not able to hear any difference from the original and the 5x looped sample.<br />
<br />
I used two different set-ups with different speakers and amplifiers, and I used headphones.<br />
<br />
It might be interesting to observe that the recording loop includes the DAC and pre in a commercial avr.<br />
<br />
To test that the method actually can detect differences in sound quality I encoded 128K mp3-samples and compared those to the original.<br />
<br />
All mp3-files tested positive.<br />
<br />
<br />
<div class="separator" style="clear: both; text-align: left;">
<i>The instrumentation is verified by abx testing of Instrumentation for playback and Recorder - the green boxes:</i></div>
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</div>
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<a href="http://2.bp.blogspot.com/-faUMY8_ccm4/VQOIWF-5fjI/AAAAAAAAARs/xKQcGcCfOQI/s1600/abxinstrumentation.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-faUMY8_ccm4/VQOIWF-5fjI/AAAAAAAAARs/xKQcGcCfOQI/s1600/abxinstrumentation.png" height="480" width="640" /> </a></div>
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<br />
<br />
<h3>
Amplifier testing </h3>
I recorded 3 amplifiers, they are quite different in topology and also measures different, though amp 1 and the C15 both measure very good on parameters assumed to have significance for sound quality.<br />
<br />
The problem now is that I have a very hard time trying to hear any difference between any of the amplifiers and the original sample.<br />
<br />
I uploaded sample files to the web site, they should be accessible by typing this link:<br />
<a href="http://www.kvalsvoll.com/Articles/abx/">www.kvalsvoll.com/Articles/abx/</a><br />
<br />
They are tagged with a very brief descriptive title.<br />
<br />
Start by looking at the tuttabella_test files, do an abx of the mp3 - it is harder than you think..<br />
<br />
The sample files are music and signal samples, in original version and sampled from the loudspeaker output of the amplifiers.<br />
<br />
Amp 1 is a very good commercial amplifier.<br />
Amp 2 is a low-budget avr.<br />
C15 is a 15W design by me.<br />
<br />
The music samples are chosen to cover different genres and style, but also for ability to reveal differences. <br />
Lots of high frequencies and voices in the Tutta Bella should be good for this purpose, the Stinky and Humming samples are more electronic and jazz-funk style with dynamics and full frequency range. <br />
<br />
The 19K+20K signals reveal high-frequency intermodulation. <br />
If you can not hear above 19K, all you hear is distortion, younger people may find it very annoying. <br />
The distortion will sound like high-frequency hiss, and a tone at lower frequency, more specific 1KHz. <br />
<br />
The 4K+10K+16K is meant to reveal high frequency distortion, mainly intermodulation, while the distortion-generating tones are also clearly audible. <br />
The distortion will sound like high frequency hiss, and a metallic tone. <br />
The tones are very annoying to listen to, and you will need to listen quite loud to have any chance of hearing any distortion. <br />
<br />
WARNING:<br />
Some of the files contain signals that may or may not be audible - DO NOT TURN UP THE VOLUME BEYOND NORMAL LOUD LISTENING LEVEL.<br />
<br />
You may end up destroying tweeters or amplifiers, be careful.<br />
<br />
<br />
Update 20.03.2015:<br />
All music samples were recorded with the amplifier playing at a decent volume into a real loudspeaker load - just like you would normally listen to music.<br />
<br />
Level was set to -3dB below clipping for the small C15 amplifier for 0dBFS from digital source material. This equals a peak level of 10W into a 8 ohm load. <br />
<br />
<br />
<h3>
Not conclusive </h3>
I have not yet managed to get a positive result for the music samples with amplifiers.<br />
<br />
I made the im_* test signals to see if some very nasty test signals works better.<br />
<br />
And they do - I can verify a difference between amplifiers and original for those signals, which is interesting, because that indicates a possibility for audible differences in amplifiers. <br />
<br />
Further experiments could be to record amplifiers looped several times, a 4x loop will increase nonlinear distortions by 12dB, while noise only increases 6dB. <br />
If this is enough to clearly reveal differences in sound, it may be used to learn and train hearing perception because you now know what to listen for. <br />
<br />
<br />
<br />
Update 23.03.2015:<br />
<br />
Sample files updated due to an error on all 44.1K sample files, the error is audible on the multitone samples im2, im3.<br />
<br />
<br />
Music samples are now gain matched within 0.1dB.<br />
<br />
Additional samples from instrumentation test loop added, these are labeled xxx_test. <br />
The 5x loop test is removed, now replaced by an updated 4x loop test. <br />
<br />
It is recommended to update your sample files if you already have downloaded any previous version.<br />
<br />
Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-7755461481921678192015-01-11T00:36:00.000+01:002015-01-11T00:36:10.690+01:00Center distance adjustment done correct<br />
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<a href="http://2.bp.blogspot.com/-uoAAdjUHuoc/VLGvKo-iPqI/AAAAAAAAAQU/CRv-euYvxSo/s1600/center2.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-uoAAdjUHuoc/VLGvKo-iPqI/AAAAAAAAAQU/CRv-euYvxSo/s1600/center2.jpg" height="320" width="317" /></a></div>
<br />
<br />
<span style="font-size: large;"><i><b><span style="color: #999999;">Learn how to set the center distance distance correctly to get the best sound.</span></b></i></span><br />
<br />
<br />
<br />
<h3>
Center distance setting </h3>
The center distance is a setting in the processor/AVR, affecting time delay of the center channel relative to the other speakers. <br />The value is set by automatic calibration, or manually, to the physical distance from the listening position to the center channel speaker. <br />We will see how more accurate fine adjustment of this distance can improve sound quality and how to do it. <br />
<br />
<h3>
Effect of center distance</h3>
The distance setting affects the timing of the signal to the center, and thus the summation of signals across the front stage. <br />If the three L, C, R front speakers have different timing, the summed frequency response will not be correct. <br />In particular sounds that are panned across the front will be affected. <br /><br />If the phase response from the center is different from the L R mains speakers, it will not be possible to get a smooth total response. <br />The concept of "timber matched" speakers is quite misunderstood, as it is not the typical small differences in frequency response amplitude that causes problems, but differences in phase response and off-axis radiation. <br />The center speaker must have a phase response and radiation pattern similar to the L R speakers to be able to provide seamless front stage sound. <br /><br />If the distance is far off, more than 20cm, the low frequency response will be affected. <br />Smaller errors down to around 2cm is perceived as loss of focus and clarity at higher frequencies, for signals spread out on all front speakers. <br />For movie dialogue recorded only in the center channel there is no difference, even for large deviations.<br />So, for those hoping this is a way to move the center sound image further away from the listening position, to make it more similar to using a phantom center, unfortunately that does not work. <br /><br />
<h3>
How to verify center distance</h3>
We can use a correlated pink noise signal played through all front channels and monitor the frequency response to see if the channels sum correctly. <br />Wrong timing will show up as comb filtering, visible as dips in the response. <br /><br />
<h3>
How to adjust center distance </h3>
Start up your functional REW or similar acoustic measurement set-up, and open the RTA real-time analyzer. <br />We will use correlated pink-noise for measurement signal: <br /><br /><a href="http://www.kvalsvoll.com/Articles/TestSignals/pn_full_fr_-20dBFS_-23dBrms_1min_LR_correlated.flac">Correlated pink noise signal for LR</a><br /><a href="http://www.kvalsvoll.com/Articles/TestSignals/pn_full_fr_-20dBFS_-23dBrms_1min_LCR_correlated.flac">Correlated pink noise signal for LCR</a><br />
<br />You can create your own correlated noise signals by first making one channel pink noise, then copy this signal to the other channels. <br />
<br />Frequency response graphs shown are from RTA with settings for quick and reasonably correct presentation of the situation above around 1KHz, at low frequencies the graphs are not accurate. <br /><br />First, we must align the microphone exactly between the front L and R at the listening position. <br />Do this by playing a correlated pink noise signal in L and R, and move the microphone sideways until the response is most flat at high frequencies. <br /><br />Mic alignment: Initially, the mic is far off: <br />
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<a href="http://4.bp.blogspot.com/-JLJniucIEQQ/VLGvNA6gPAI/AAAAAAAAAQo/blHcHVmKAlU/s1600/lr%2Bfar%2Boff.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-JLJniucIEQQ/VLGvNA6gPAI/AAAAAAAAAQo/blHcHVmKAlU/s1600/lr%2Bfar%2Boff.png" /></a></div>
<br /><br />Mic alignment: Getting closer: <br />
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<a href="http://1.bp.blogspot.com/-herLyeI9VQE/VLGvNER0RMI/AAAAAAAAAQs/z6IlApl9pfQ/s1600/lr%2Bcloser.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-herLyeI9VQE/VLGvNER0RMI/AAAAAAAAAQs/z6IlApl9pfQ/s1600/lr%2Bcloser.png" /></a></div>
<br />Mic alignment: After fine adjustment within approximately 5mm:<br />
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<a href="http://4.bp.blogspot.com/-BeM6NCdrpYQ/VLGvNAcjEzI/AAAAAAAAAQw/Bwl5b4turIg/s1600/lr%2Bcorrect.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-BeM6NCdrpYQ/VLGvNAcjEzI/AAAAAAAAAQw/Bwl5b4turIg/s1600/lr%2Bcorrect.png" /></a></div>
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<br />
<br />
Set the center channel distance to a reasonably correct value, within say 20 to 50cm. <br />Also check that the center channel level matches the front L and R, and adjust if necessary. <br />Then play a correlated pink noise signal in all L, C, R channels, and adjust the center channel distance in small 1cm increments until the response is as flat as possible. <br />It may show a slight roll-off at higher frequencies, as even small differences in phase response between center and L, R will have significance. <br /><br />Center distance: Initally, we see the signals do not sum up correctly, there is visible comb filtering: <br />
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<a href="http://1.bp.blogspot.com/-BmSw5F3hFzE/VLGvPoz4E-I/AAAAAAAAAQ8/US3-N-upAT0/s1600/c%2Bwrong.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-BmSw5F3hFzE/VLGvPoz4E-I/AAAAAAAAAQ8/US3-N-upAT0/s1600/c%2Bwrong.png" /></a></div>
<br /><br />Center distance: After adjusting the center distance within +-1cm: <br />
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<a href="http://2.bp.blogspot.com/-hWvXTqmN_yQ/VLGvP-QT3FI/AAAAAAAAARA/jSGUXJ59zd4/s1600/c%2Bcorrect.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-hWvXTqmN_yQ/VLGvP-QT3FI/AAAAAAAAARA/jSGUXJ59zd4/s1600/c%2Bcorrect.png" /></a></div>
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<br />
<br />
<h3>
Subwoofer system integration </h3>
At low frequencies the integration to the subwoofer system is affected, and this is solved by adjusting the distance for the subwoofer system. <br />Subwoofer distance adjustment will be covered in a coming article. <br />
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<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-20388390823737480862014-09-04T23:17:00.000+02:002014-09-05T22:44:49.609+02:00Bass EQ for Movies - How to improve sound quality on bass filtered movies<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-bngEUR3e6F8/VAjNxtjJo3I/AAAAAAAAANo/Otv_Xwc6TlM/s1600/bass_eq.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-bngEUR3e6F8/VAjNxtjJo3I/AAAAAAAAANo/Otv_Xwc6TlM/s320/bass_eq.jpg" height="260" width="400" /></a></div>
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<a href="http://3.bp.blogspot.com/-JzSmdgAzyj0/VAjOOdxlEyI/AAAAAAAAAPQ/R9pumQi7Lj0/s1600/kontiki_storm_zoom.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div>
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<span style="font-size: large;"><i><b><span style="color: #999999;">Would it not be great if you could bring back the lost bass in you favorite movies? <br />
Well, perhaps you can. <br /><br />
By applying equalization customized for each movie during playback, it is possible to dig out some of the low bass lost due to filtering and processing in the studio.
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<h3>
Why Bass EQ</h3>
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When movies are mixed in the studio, the sound will be adjusted according to what they hear in that studio. <br />
Sometimes limitations in the playback equipment, such as speaker system, will lead to adjustments that will compromise sound quality. <br />
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Typical examples of such undesired adjustments are high-pass filtering that removes the lowest frequency content.<br />
On a limited system this may sound better, because the removal of content that can not be reproduced anyway will increase headroom for the mid and upper bass frequencies. <br />
When played back on a full frequency range system the filtered version looses weight and impact, and also tend to sound less natural. <br />
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If this filtering is done in one of the very final stages of production, then it is a good possibility that at least some of the filtered content can be retrieved. <br />
This is what Bass EQ tries to do. <br />
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The better your playback system is, and if you also like it loud, like 0dB/reference, then the difference will be very significant, and on some movies the whole experience is lifted to another level. <br />
But also if you play at lower volumes, say -20dB, perhaps you have some smaller but still nice and good quality subwoofers, then the difference will most certainly be very noticeable. <br />
This is not only about more shake and physical impact at house-wrecking volumes, the overall sound quality is improved when the natural wide frequency range of is restored. <br />
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Example frequency spectrum plots playing this scene from the movie Battleship:<br />
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<a href="http://2.bp.blogspot.com/-fnvTqPWWHxs/VAjQ26IUjWI/AAAAAAAAAPc/kUrsj6sR5-w/s1600/bs_1.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-fnvTqPWWHxs/VAjQ26IUjWI/AAAAAAAAAPc/kUrsj6sR5-w/s1600/bs_1.jpg" /></a></div>
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Battleship, original and Battleship with Bass EQ playback:<br />
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<a href="http://1.bp.blogspot.com/-8Xbwy8A2P18/VAjRXl_iG-I/AAAAAAAAAPs/HQK88Z1IZ10/s1600/bs_boom_rta.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-8Xbwy8A2P18/VAjRXl_iG-I/AAAAAAAAAPs/HQK88Z1IZ10/s1600/bs_boom_rta.png" height="173" width="400" /></a></div>
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<a href="http://2.bp.blogspot.com/-TA7P4fPHhl0/VAjRZhpoeXI/AAAAAAAAAP0/dl9FjWN_afc/s1600/bs_boom_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-TA7P4fPHhl0/VAjRZhpoeXI/AAAAAAAAAP0/dl9FjWN_afc/s1600/bs_boom_zoom.png" height="181" width="400" /></a></div>
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There is a huge difference in output at low frequencies, and listening easily reveals that the perceived increase in sound quality is significant and very far from subtle.<br />
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<h3>
How to Bass EQ </h3>
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You must be able to implement equalization according to the Bass EQ graph for each individual movie. <br />
This can be done in a DSP, if you have something like that in the playback chain. <br />
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In a bass-managed system the Bass EQ can be implemented on the subwoofer channel. <br />
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Computer playback is increasing in popularity, and it will eventually be the preferred playback device for all media content. <br />
Then it is likely that equalization can be done very flexible and accurate using a plug-in or built-in processing in the player software. <br />
JRiver media center is an example of player software that can do Bass EQ with individual settings for each move. <br />
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A simple graphical equalizer or bass tone control will not be able to provide Bass EQ. <br />
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To verify your equalizer setting you can play a pink noise file and compare the frequency responses - the unfiltered pink noise should be flat, and pink noise with Bass EQ should look similar to the Bass EQ curve. <br />
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Some movies require a very large boost at low frequencies, perhaps in the order +20dB gain below 20Hz. <br />
This requires careful attention to what you are doing. <br />
If such a filter is left in unintentionally, and you play a movie with flat full frequency content, something will overload. <br />
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Some movies are quite heavy in the mid bass region, equalizing this down will gain some headroom for the low bass as well as improving the overall spectral balance. <br />
If there is noise at frequencies below usable output, say around 10Hz and below, then this can be removed using a high pass filter, and some more headroom is gained. <br />
If the sound track is mixed very loud and dynamically compressed, there may not be enough headroom for the low bass we bring back, and the only solution is to reduce the level before applying the Bass EQ. <br />
The lost gain is restored later in the chain, perhaps as simple as adjusting the master volume. <br />
Exactly how this is done depends on what it used for equalization; different dsp and software may require different approaches. <br />
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<h3>
How to recognize good candidates for Bass EQ and what to fix </h3>
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Any movie where sound effects and bass is lacking in weight are potential candidates. <br />
Looking at the Peak-Average graph from the The Low Frequency Content Thread (films, games, music, etc) thread can tell a lot about how a movie sounds. <br />
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Kon-Tiki is a film with a good sound track utilizing the whole frequency spectrum, observe that the curve is a slightly tilted line extending all the way down to the very lowest frequencies:<br />
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<a href="http://3.bp.blogspot.com/-E8hZcZu-bQ0/VAjR51C3snI/AAAAAAAAAP8/69vtPDmUlAM/s1600/KonTiki_pavg.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-E8hZcZu-bQ0/VAjR51C3snI/AAAAAAAAAP8/69vtPDmUlAM/s1600/KonTiki_pavg.jpg" height="223" width="400" /></a></div>
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The storm scene has content all the way down:<br />
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<a href="http://2.bp.blogspot.com/-rji4BgHthbQ/VAjOMnszz8I/AAAAAAAAAPE/72orymISYQQ/s1600/KonTiki_storm.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-rji4BgHthbQ/VAjOMnszz8I/AAAAAAAAAPE/72orymISYQQ/s1600/KonTiki_storm.jpg" /></a><br />
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<a href="http://3.bp.blogspot.com/-YNA6WFdNZV8/VAjONh1eA4I/AAAAAAAAAPM/Td5hUq8A0b8/s1600/kontiki_storm_rta.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-YNA6WFdNZV8/VAjONh1eA4I/AAAAAAAAAPM/Td5hUq8A0b8/s1600/kontiki_storm_rta.png" height="198" width="400" /></a></div>
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<a href="http://3.bp.blogspot.com/-JzSmdgAzyj0/VAjOOdxlEyI/AAAAAAAAAPU/eUhSYKjs-c4/s1600/kontiki_storm_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-JzSmdgAzyj0/VAjOOdxlEyI/AAAAAAAAAPU/eUhSYKjs-c4/s1600/kontiki_storm_zoom.png" height="190" width="400" /></a></div>
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This film does not need any Bass EQ.<br />
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Battleship has met with an accident somewhere in the sound-making process:<br />
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<a href="http://2.bp.blogspot.com/-J8rsrgFvgAE/VAjSQ-1t6HI/AAAAAAAAAQE/1N6oXLroJh8/s1600/battleship_pva.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-J8rsrgFvgAE/VAjSQ-1t6HI/AAAAAAAAAQE/1N6oXLroJh8/s1600/battleship_pva.jpg" height="223" width="400" /></a></div>
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There is an obvious drop right below 35Hz, looks like a steep high-pass filter has been applied. <br />
This is something to work on for Bass EQ. <br />
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A good target response is likely an approximately tilted straight line, that extends as low in frequency as possible. <br />
Start with applying equalization that bring the Peak-Average curve closer to this straight tilted response. <br />
Evaluation by listening is necessary to determine appropriate equalization, and care must be taken to ensure not to clip the signal anywhere in the chain. <br />
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How low in frequency should you try to equalize to flat. <br />
Depends on the original sound design, and whether there is any content to dig out, it may be buried in noise at the very lowest frequencies. <br />
Fixing something destroyed with a 30Hz filter and mangaging to retrieve flat down to 20Hz can make a huge difference. <br />
If you can extend it down to around 15Hz, even better. <br />
Below around 15Hz is questionable, certainly depends on your playback system, as tactile feedback from floor or moving house structure may be required to notice it at all. <br />
The lower you go the greater the risc of amplifying noise instead of usable content, and if you can bring a sound track with virtually no low bass back to life with significant content down to 15Hz, I would say that is a very good achievement. <br />
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Gravity, opening scenes (RTA from playback):<br />
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<a href="http://1.bp.blogspot.com/-czJKQ24agtA/VAjOCOt_8YI/AAAAAAAAAOk/uWPy1RH2E5E/s1600/gravity.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-czJKQ24agtA/VAjOCOt_8YI/AAAAAAAAAOk/uWPy1RH2E5E/s1600/gravity.jpg" /></a></div>
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<a href="http://4.bp.blogspot.com/-kN-Gu9TRJTE/VAjOIFb6z5I/AAAAAAAAAO0/7SfA-Ls0Jpo/s1600/gravity_rta.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-kN-Gu9TRJTE/VAjOIFb6z5I/AAAAAAAAAO0/7SfA-Ls0Jpo/s1600/gravity_rta.png" height="197" width="400" /></a></div>
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<a href="http://1.bp.blogspot.com/-4n-cC684O9U/VAjOLDE40oI/AAAAAAAAAO8/OPwIHsFy1a4/s1600/gravity_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-4n-cC684O9U/VAjOLDE40oI/AAAAAAAAAO8/OPwIHsFy1a4/s1600/gravity_zoom.png" height="181" width="400" /></a></div>
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This film has a droning, constant tone around 20Hz, as can be seen in the curve. <br />
This is part of the sound design. <br />
The level below 20Hz drops off very quickly, but it is not likely that equalization can bring improvements, because likely there is no content that has been removed. <br />
The relationship between frequency and time dictates that continuous tones, which have a long time span, are narrow in frequency distribution. <br />
Impulse like transients, like cannons and gunshots, have short time span and a wide frequency distribution. <br />
If there are no impulses, there may not be low frequency content to retrieve. <br />
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When the Explorer is hit by the debris, there are sound effects added that adds to the sensation of the incident, these sounds are more dynamic and impulse-like:<br />
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<a href="http://4.bp.blogspot.com/-u9Ld24zu_zI/VAjOFMzikbI/AAAAAAAAAOs/icC4yaJmpHg/s1600/gravity_hit_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-u9Ld24zu_zI/VAjOFMzikbI/AAAAAAAAAOs/icC4yaJmpHg/s1600/gravity_hit_zoom.png" height="181" width="400" /></a></div>
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The spectrum reveals that there is content below the 20Hz drone, and that this content may have been filtered using a steep high pass around 20Hz. <br />
Gravity is another candidate for Bass EQ. <br />
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Avatar, flight scene (RTA from playback):<br />
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<a href="http://1.bp.blogspot.com/-KfzDDK91uZY/VAjN0nnhBHI/AAAAAAAAAN0/cBQo-EHKFb0/s1600/avatar_flight.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-KfzDDK91uZY/VAjN0nnhBHI/AAAAAAAAAN0/cBQo-EHKFb0/s1600/avatar_flight.jpg" /></a></div>
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<a href="http://2.bp.blogspot.com/-gGJlyVENm2Q/VAjN2dMmsBI/AAAAAAAAAN8/pLYHVvl1g6c/s1600/avatar_flight_rta.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-gGJlyVENm2Q/VAjN2dMmsBI/AAAAAAAAAN8/pLYHVvl1g6c/s1600/avatar_flight_rta.png" height="197" width="400" /></a></div>
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<a href="http://1.bp.blogspot.com/-xOhYffzTGKc/VAjN37MKw7I/AAAAAAAAAOE/gdP7PSGYdOM/s1600/avatar_flight_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-xOhYffzTGKc/VAjN37MKw7I/AAAAAAAAAOE/gdP7PSGYdOM/s1600/avatar_flight_zoom.png" height="181" width="400" /></a></div>
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This scene sounds good, the feeling of realism and athmosphere is good. <br />
Right at the end of this scene, where the plane drops down the cliff, there is a sense of weightlessness, making it feel like you are on the plane. <br />
The spectrum reveals why this effect is so good - there is significant content at the very lowest frequencies, peaking around 13Hz. <br />
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Avatar, monster stomp-stomp (RTA from playback):<br />
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<a href="http://1.bp.blogspot.com/-1t5QFl_NJls/VAjN9lxuR_I/AAAAAAAAAOc/yVwMC84Rj_o/s1600/avatar_stomp.jpg" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-1t5QFl_NJls/VAjN9lxuR_I/AAAAAAAAAOc/yVwMC84Rj_o/s1600/avatar_stomp.jpg" /></a></div>
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<a href="http://4.bp.blogspot.com/-SAi3b1EZJ54/VAjN6GltH8I/AAAAAAAAAOM/szILZvi373s/s1600/avatar_stampstamp_rta.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-SAi3b1EZJ54/VAjN6GltH8I/AAAAAAAAAOM/szILZvi373s/s1600/avatar_stampstamp_rta.png" height="197" width="400" /></a></div>
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<a href="http://1.bp.blogspot.com/-L7lCa62MlbA/VAjN7oMhELI/AAAAAAAAAOU/d0AxvhP7ICU/s1600/avatar_stampstamp_zoom.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-L7lCa62MlbA/VAjN7oMhELI/AAAAAAAAAOU/d0AxvhP7ICU/s1600/avatar_stampstamp_zoom.png" height="181" width="400" /></a></div>
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Here the stomps sounds rather boomy and does not have the appropriate feeling of weight and impact. <br />
The spectrum reveals why - the low frequency content below 25Hz is removed. <br />
Considering the previous flight scene, the conclusion is that finding the best Bass EQ for Avatar will be a compromise.<br />
Some scenes could benefit from a huge low-frequency boost, but then other scenes would sound horrible with too much in the low end. <br />
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<h3>
Movies improving with Bass EQ</h3>
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There is now a thread at data-bass listing Movies with Bass EQ: <br />
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<a href="http://data-bass.ipbhost.com/index.php?/topic/285-the-bass-eq-for-movies-thread/">The Bass EQ for Movies thread</a> <br />
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<a href="http://www.data-bass.com/home">Data-bass</a> also hosts lots of other content about movies, subwoofers and sound quality related topics. <br />
<a href="http://data-bass.ipbhost.com/index.php?/topic/12-the-low-frequency-content-thread-films-games-music-etc/">The Low Frequency Content thread</a> is a highly regarded source for information about movie sound tracks.Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-60144737018846585942014-08-08T00:10:00.001+02:002014-08-08T00:10:53.987+02:00My Bandcamp Music<br />
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<a href="http://4.bp.blogspot.com/-C0eg4Wt8i9w/U-Pw6o9GwEI/AAAAAAAAANY/rCL4Q7lKkLo/s1600/mybandcamp.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-C0eg4Wt8i9w/U-Pw6o9GwEI/AAAAAAAAANY/rCL4Q7lKkLo/s1600/mybandcamp.png" height="317" width="640" /> </a></div>
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<span style="font-size: large;"><i><b><span style="color: #999999;">On <a href="http://bandcamp.com/oyvindkvalsvoll">Bandcamp.com</a> I have found lots of interesting music of very high quality, music that would never have reached me through old media distribution channels. </span></b></i></span><br />
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A better way for music distribution</h3>
<a href="http://bandcamp.com/">Bandcamp</a> is a web-site where you can listen to and buy music.<br />
You can buy for download directly to your computer, no need to hassle with ripping CDs any more, and lossless formats are available so you do not have to worry about encoding quality. <br />
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Today, when physical media such as CD is disappearing, many find that streaming services like Spotify is a good source for music. <br />
However, there are very good reasons to prefer services where you buy and acquire the music and download it for local storage, on your own hard drive. <br />
At least for the enthusiast, who cares about quality, this is the only way to ensure you have the right version of your favourite albums, and it will not suddenly go away if the streaming service goes down or you simply loose your internet connection. <br />
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I present for you some examples of music I have found, and describes what makes those special with respect to how they sound. <br />
As I say on my Bandcamp page; "My review comments focus on sound - not many do so, and others are far better on the music part." <br />
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Electronic </h3>
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<a href="http://1.bp.blogspot.com/-BkCcGrH6Ei0/U-Pw6WuSo6I/AAAAAAAAANE/F60-fqmKij4/s1600/flashbulb.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-BkCcGrH6Ei0/U-Pw6WuSo6I/AAAAAAAAANE/F60-fqmKij4/s1600/flashbulb.png" height="200" width="200" /></a></div>
<b>The Flashbulb - Reunion: </b><br />
A masterpiece of dynamics and excellent sound production. <br />
Note the impact of the drums of tracks like Oak Lawn UFO and Walking Irrevocable. <br />
But be warned, this is electronic, and everything is allowed, sometimes effects like distortion and changes in tonal balance are used in ways that can seriously disturb the typicial audiophile ears.<br />
The dynamics and general composition makes it possible to play very loud and it will still sound quite pleasant, there is no Loudness-war disease here. <br />
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<a href="http://3.bp.blogspot.com/-aLNu_2lBYAo/U-Pw5qCeCII/AAAAAAAAAMw/UZSUkggSrGo/s1600/emancipator.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-aLNu_2lBYAo/U-Pw5qCeCII/AAAAAAAAAMw/UZSUkggSrGo/s1600/emancipator.png" height="200" width="200" /></a></div>
<b>Emancipator - Safe In The Steep Cliffs: </b><br />
What makes this special is the lively and exciting sound.<br />
Listen to, or rather, feel, the drums on Rattlesnakes, note the big difference in both sound and tactile feel between the sharper smaller drums and the larger bass drum.<br />
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<a href="http://2.bp.blogspot.com/-Twy26ZpDSx4/U-Pw2TmIAvI/AAAAAAAAAMo/5ky02gDNZu0/s1600/antilogy.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-Twy26ZpDSx4/U-Pw2TmIAvI/AAAAAAAAAMo/5ky02gDNZu0/s1600/antilogy.png" height="200" width="200" /></a></div>
<b>Panda Dub - Antilogy: </b><br />
A dub production with unusual good overall sound quality, dynamic and detailed, pleasant to play loud. <br />
If you like this one you should check out Panda Dub's other releases, particularly the older ones. <br />
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Instrumental </h3>
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<a href="http://2.bp.blogspot.com/-j5gSyX6dVhE/U-Pw5ogTU3I/AAAAAAAAAM8/bVLKfAwcBXM/s1600/emily.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-j5gSyX6dVhE/U-Pw5ogTU3I/AAAAAAAAAM8/bVLKfAwcBXM/s1600/emily.png" height="200" width="200" /></a></div>
<b>Emily Davidsson - BASS SOUNDS: Music for Unaccompanied Cello from the Early Baroque: </b><br />
This is a musical and technical masterpiece. <br />
If you think this should be easy to do right - only one instrument, then check out some other releases in the same genre of classical music with few instruments, nowadays quite many of those are destroyed by bad production. <br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-e1mIhrmy9YU/U-Pw6wWycaI/AAAAAAAAANM/KPAaUFpCrL4/s1600/oldtimes.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-e1mIhrmy9YU/U-Pw6wWycaI/AAAAAAAAANM/KPAaUFpCrL4/s1600/oldtimes.png" height="200" width="200" /></a></div>
<b>Seems Like Old Times: </b><br />
A Jazz band in my room, simply. <br />
No attempts to polish or amplify or make things sound bigger than they are. <br />
And it is this simple and plain approach that actually achieves what others with large budgets and names try to do using boosts in the bass, compression, limiters, more compression, and eventually ending up with a flat and unnatural sound. <br />
Turn it up and this sounds huge, dynamic and natural, it achieves to transfer some of the energy and liveliness of live music. <br />
<br />
<br />
<br />
<br />
<br />
<br />
<h3>
Join and find hidden treasures yourself</h3>
<br />
I have no affiliation to <a href="http://bandcamp.com/">Bandcamp.com</a>, I only encourage you to join and support the music and distribution platform, contribute by posting about music you find there, and enjoy the diversity of popular and established artists as well as the new or specialized ones. <br />
Look at my personal collection at <a href="http://bandcamp.com/oyvindkvalsvoll">bandcamp.com/oyvindkvalsvoll</a> to see what I have found, and then you can use the <a href="http://bandcamp.com/discover">bandcamp.com/discover</a> to search for music. <br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-ihtScB_vdXg/U-Pw5pDVo-I/AAAAAAAAAM0/-c6d7PMaYBQ/s1600/discover.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-ihtScB_vdXg/U-Pw5pDVo-I/AAAAAAAAAM0/-c6d7PMaYBQ/s1600/discover.png" height="187" width="400" /></a></div>
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<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-11804030337557683632014-07-06T01:34:00.000+02:002014-07-06T01:34:07.990+02:00Pink Noise Calibration<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-EcSb_ceOM9Q/U7iDVsPi7TI/AAAAAAAAAMA/f6eW2J6ruHI/s1600/bilde.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-EcSb_ceOM9Q/U7iDVsPi7TI/AAAAAAAAAMA/f6eW2J6ruHI/s1600/bilde.png" height="314" width="640" /></a></div>
<br />
<br />
<br />
<span style="font-size: large;"><i><b><span style="color: #999999;">Measuring more than one speaker and getting predictable and usable results can be challenging. <br /> </span></b></i></span><br />
<span style="font-size: large;"><i><b><span style="color: #999999;">Using pink noise and a real-time analyzer makes it easy to check level and frequency response, and you can move the mic around to measure at different locations and still get meaningful observations.</span></b></i></span><br />
<br />
<br />
<h3>
Purpose </h3>
When setting up a sound system you need measurements to verify what is going on with the sound, and the frequency response is the most important characteristic. <br />
Location of listening positions and speakers, eq settings, room correction and room acoustics all affect the response. <br />
To be able to make adjustments in the right direction it is necessary to measure. <br />
<br />
<br />
<h3>
Problems with sine wave sweeps and multiple sound sources </h3>
Sound from more than one speaker will sum up in strange patterns depending on type of sound, room acoustics and microphone position. <br />
It is possible to measure two speakers with sine sweep, but that requires some understanding of what is going on, and the mic must be located within few mm exactly between the two speakers. <br />
<br />
<br />
<h3>
The uncorrelated pink noise solution</h3>
By using uncorrelated pink noise sent to all speakers the individual sound sources will sum more correctly like music or movie sound.<br />
The frequency response can be observed using a real-time analyzer, which means you can see the frequency response changing when moving the mic. <br />
<br />
By having multichannel pink noise files with different channel configurations it is quick and easy to measure different speakers in a surround system. <br />
<br />
<br />
<h3>
Limitations</h3>
Pink noise and real-time analyzer method can only verify level and frequency response. <br />
For other measurements, such as distortion and impulse response, it is necessary to measure with sine sweep, each speaker individually. <br />
Also, there is no possibility to isolate the speakers direct sound from room reflections using gating, the pink noise will always measure all sound including all room contribution. <br />
<br />
<br />
<h3>
Tools</h3>
You need <a href="http://www.roomeqwizard.com/">REW measurement software</a> and a calibrated microphone. <br />
The software is free, and a good mic is cheap compared to what many are willing to pay for potential upgrades to their sound system. <br />
<br />
Pink noise files can be downloaded from my web site: <br />
<br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%20full_fr%20-20dBFS%2015s%207_1.flac">pn full_fr -20dBFS 15s 7_1.flac</a><br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%20full_fr%20-20dBFS%2020s%20L+R.flac">pn full_fr -20dBFS 20s L+R.flac</a><br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%20full_fr%20-20dBFS%2020s%20LCR.flac">pn full_fr -20dBFS 20s LCR.flac</a><br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%20full_fr%20-20dBFS%2020s%20C.flac">pn full_fr -20dBFS 20s C.flac</a><br />
<br />
<br />
<h3>
How to measure</h3>
- Play the pink noise file that corresponds to the speakers you want to measure. <br />
- Open the RTA in REW<br />
- Select Mode: RTA 1/48 octave<br />
- Select FFT Length: 32768<br />
- Select Averages: Exponential 0.88<br />
<br />
A scaling where the 5dB/div lines are visible is fine. <br />
<br />
Now you will see the frequency response being continuously updated, and you can move the mic around to check various positions.<br />
<br />
A "good" response is one that most closely follows a tilted line, where the amount of tilt depends on room acoustics and preference. <br />
Typical tilt is from 0dB (flat) up to around 10dB from 20Hz-20KHz, and generally a more live room has more tilt. <br />
If you can get within +-5dB that is generally considered good. <br />
<br />
For single speaker measurements you can use the PN Pink Noise generator in REW, for more speakers this will not work because the noise signals will be correlated and will not sum up correctly. <br />
<br />
<i>REW measurement software RTA window</i><br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-MgunWICg4ls/U7iDWYMdk1I/AAAAAAAAAMU/0HWzNo4RG_E/s1600/rta.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-MgunWICg4ls/U7iDWYMdk1I/AAAAAAAAAMU/0HWzNo4RG_E/s1600/rta.png" height="361" width="640" /></a></div>
<br />
<br />
<h3>
Example measurements</h3>
<br />
<b>7.1 System at multiple seats</b><br />
<br />
I wanted to verify the response in The Moderate Cinema from all speakers, and see how it changes at different seats. <br />
Response is nice and even across the mid range, the roll-off above 10KHz is due to the surround speakers falling off because they are not on-axis. <br />
At low frequencies the better seats are good, but the two on the far left have some large dips. <br />
<br />
<i>Pink noise all 7.1 channels, seat 1</i><br />
<a href="http://1.bp.blogspot.com/-7dE9OYWZOnI/U7iDUcRTncI/AAAAAAAAAL0/-3TFktn8A6E/s1600/7_1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-7dE9OYWZOnI/U7iDUcRTncI/AAAAAAAAAL0/-3TFktn8A6E/s1600/7_1.png" height="340" width="640" /></a><i> </i><br />
<br />
<i>Seats 1 to 5</i><br />
<a href="http://1.bp.blogspot.com/-n0EqW_vs8Kw/U7iDURkHjFI/AAAAAAAAAMc/T30R04fUpu4/s1600/7_1+1_5.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-n0EqW_vs8Kw/U7iDURkHjFI/AAAAAAAAAMc/T30R04fUpu4/s1600/7_1+1_5.png" height="340" width="640" /></a>
<br />
<br />
<i>Seats 1 to 5, 1/6 oct smoothing</i><br />
<i><a href="http://3.bp.blogspot.com/-S-2ChXYtIcw/U7iDUdOVW_I/AAAAAAAAALw/Nr4LP1LjHwY/s1600/7_1+1_5+smooth.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-S-2ChXYtIcw/U7iDUdOVW_I/AAAAAAAAALw/Nr4LP1LjHwY/s1600/7_1+1_5+smooth.png" height="340" width="640" /></a> </i><br />
<br />
<br />
<a href="http://3.bp.blogspot.com/-S-2ChXYtIcw/U7iDUdOVW_I/AAAAAAAAALw/Nr4LP1LjHwY/s1600/7_1+1_5+smooth.png" style="margin-left: 1em; margin-right: 1em;"></a><br />
<b><br />L+R at multiple seats</b><br />
<br />
The front L and R speakers are the most important, and especially for music it is important to have good linearity in the response for these. <br />
For music listening we choose fewer seats, and see that seats 1, 2 and 4 has reasonably good response. <br />
<br />
<i>L and R, seat 1</i><br />
<a href="http://1.bp.blogspot.com/-juGtJwYvGW0/U7iDWQ61-3I/AAAAAAAAAMM/iOVJd9jjWuk/s1600/l%252Br.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-juGtJwYvGW0/U7iDWQ61-3I/AAAAAAAAAMM/iOVJd9jjWuk/s1600/l%252Br.png" height="340" width="640" /></a><br />
<br />
<br />
<i>L and R, seat 1, 2, 4, 1/6 oct smoothing</i><br />
<a href="http://3.bp.blogspot.com/-O6WNh04IUts/U7iDV4itcQI/AAAAAAAAAMY/KvjqmMGcKWY/s1600/l%252Br+124.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-O6WNh04IUts/U7iDV4itcQI/AAAAAAAAAMY/KvjqmMGcKWY/s1600/l%252Br+124.png" height="340" width="640" /></a>Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-71890180069681460462014-05-06T06:11:00.001+02:002014-05-06T06:12:41.418+02:00How to make Audyssey room correction work<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i></i></span></b></span><br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>How to fix a too-bright Audyssey calibration</i></span></b></span><br />
<br />
Audyssey room correction is included in many of the most popular AV-receivers. <br />
By making adjustments to reduce the effects from bad room acoustics or bad speakers, Audyssey improves sound quality. <br />
And even for good systems in good rooms there may be a significant gain in clarity and definition of the sound. <br />
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>However, limitations to the Audyssey implementations causes failure when used with some speaker and room combinations. <br /><br />I will show what goes wrong, and how to make it work.<span style="color: #999999;"><b><span style="font-size: large;"><i> </i></span></b></span> </i></span></b></span><br />
<br />
<h3>
</h3>
<h3>
Initial calibration</h3>
This system consist of controlled directivity main front speakers and 4 compact Horn subwoofers located in the corners. <br />
Distance, level and crossover settings are carefully calibrated, to give a reasonable flat tilted frequency response and volume level calibration according to 85dB SPL for -20dB master volume. <br />
<br />
After running Audyssey the tonal balance is too bright, with excessive highs. <br />
Selecting the 'Audyssey' curve only makes it worse, it ends up with a notch in the upper midrange, too bright, and the highest frequencies attenuated. <br />
<br />
Also, the automatic settings for subwoofer crossover and distance is far off, causing the bass to be very strange. <br />
<br />
All this can be confirmed by measuring the systems frequency response - which shows the loudness as a function of sound frequency. <br />
<br />
Because Audyssey internally uses a different method to find the response it uses to calculate the correction, the result will vary depending on the speaker and room interaction. <br />
For some speakers and rooms it may work, for others, not so. <br />
<br />
<br />
<i>Frequency response, No Audyssey and Audyssey Flat with automatic settings</i><br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-7jqEZ57mp0Y/U2hYoJk0poI/AAAAAAAAALM/yzSbaSUaYMw/s1600/cal_i1+audysseyflat.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-7jqEZ57mp0Y/U2hYoJk0poI/AAAAAAAAALM/yzSbaSUaYMw/s1600/cal_i1+audysseyflat.png" height="342" width="640" /></a></div>
<br />
The red curve is the calibrated system without Audyssey, a fairly even response with a slight downwards tilt as the frequency rises.<br />
<br />
The grey curve is with Audyssey Flat correction enabled, and all settings left like the automatic calibration suggested. There are severe dips in the bass range, and level above 2-3KHz is too high, causing a too bright sound balance. <br />
<br />
These curves are not smooth, they show peaks and dips caused by room reflections. They are presented like this, with 1/24 octave smoothing only, so that we can see what is going on. <br />
<br />
<br />
<h3>
Restore settings</h3>
By restoring settings for subwoofer crossover and distance and level, the bass response is restored. <br />
Crossover is set to 120Hz, distance is 5.40m. <br />
<br />
<br />
<i>Frequency response, Audyssey Flat, restored settings</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-QOexV_B1Z0Y/U2hYspAiQPI/AAAAAAAAALU/vZuHIXJSanA/s1600/cal_i1+audyssey+fixed100hz.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-QOexV_B1Z0Y/U2hYspAiQPI/AAAAAAAAALU/vZuHIXJSanA/s1600/cal_i1+audyssey+fixed100hz.png" height="342" width="640" /></a></div>
<i><br /></i>
The green curve is Audyssey Flat with tone control adjusted and crossover and distance settings restored. With no tone adjust the Audyssey Flat is equal to the grey curve above 1KHz. <br />
<br />
<br />
<h3>
Adjust tilt</h3>
By using the tone controls it is possible to fix the tilt of the frequency response to match the around 3dB/decade fall, which will also give a flat on-axis response in this room with these speakers. <br />
<br />
The tone control in this AVR is implemented in the master volume control circuit, and this same chip is used in many, if not most, newer AVRs. <br />
This means the tone control works independent of the Audyssey processing, and it also happens to follow a nice tilting curve when adjusted. <br />
<br />
Adjusting bass to +1dB and treble to -5dB causes the curves to match, adjusted by observing the frequency response measurements. <br />
It is possible to adjust this by ear, using pink noise, and adjust until the tonal balance of the noise seems the same for no Audyssey and Audyssey with tone adjustment.<i> </i><br />
<br />
<i>Frequency response, No Audyssey and Audyssey Flat with tone control adjusted tilt</i><br />
<a href="http://3.bp.blogspot.com/-1LUeYcN4HY4/U2hYx8sNjBI/AAAAAAAAALc/tvPM1oDsXVo/s1600/cal_i1+og+fixed.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-1LUeYcN4HY4/U2hYx8sNjBI/AAAAAAAAALc/tvPM1oDsXVo/s1600/cal_i1+og+fixed.png" height="342" width="640" /></a><br />
<br />
Now we can see that the tilt of the frequency response matches for both without and with Audyssey Flat enabled. The 1/1 smoothed curves show the averaged tilt of the reponses. <br />
<br />
<br />
<h3>
Further improvements</h3>
This set-up should be re-calibrated to get the best possible response in the 80-200Hz range, by selection of crossover, distance adjustment and Audyssey recalibration. <br />
Here is how I would proceed: <br />
<br />
1. Equalize the subwoofer system to flat using the subwoofer DSP. <br />
2. Run Audyssey to calibrate. <br />
3. Re-enable the house-curve on the subwoofer DSP. <br />
3. Adjust crossover and distance for subwoofer to get the best possible response with Audyssey enabled. <br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com3tag:blogger.com,1999:blog-7131957440381098047.post-5774945427484313202014-03-29T02:13:00.000+01:002014-03-29T02:13:29.995+01:00Audibility of peak limiting<br />
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>
Peak limiting and clipping is used to make music seem louder, but does it really work that way? <br />No - removing the peaks actually reduces impact and brutality and makes it sound flat and boring.
</i></span></b></span><br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-0C1Fa8LilzE/UzYZf_x1zlI/AAAAAAAAAK0/0BcCgLnMiFQ/s1600/limiter+test.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-xIhERe8znzw/UzYZhjhD1oI/AAAAAAAAAK8/CIHCN8yFhDg/s1600/music+production.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><br /></a></div>
<a href="http://3.bp.blogspot.com/-xIhERe8znzw/UzYZhjhD1oI/AAAAAAAAAK8/CIHCN8yFhDg/s1600/music+production.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-xIhERe8znzw/UzYZhjhD1oI/AAAAAAAAAK8/CIHCN8yFhDg/s1600/music+production.png" height="163" width="640" /></a><br />
<br />
<h3>
Intro</h3>
Typical sources of peak limiting in audio reproduction are loudspeakers and power amplifiers. <br />
This can obviously easily be avoided by turning it down a bit, or get larger speakers with better sensitivity. <br />
<br />
Music can also be destroyed in the production process, where removal of peaks using brickwall limiters is more common than not today. <br />
Dynamic compression, brickwall limiting and peak clipping in music is well known today as the Loudness War. <br />
The kind of signal processing used causes loss of transient peak amplitude and adds distortion. <br />
It is this type of signal destruction that is investigated here. <br />
<br />
Upon visual inspection one can see that the limited waveforms are clearly changed, and it may be difficult to understand why this is not also very easy to hear. <br />
But the loss of signal amplitude happens in a very short period of time, it is not necessarily easy to detect unless you know what to listen for. <br />
There is no apparent change in overall sound level, and the tonal balance is not changed at all.<br />
<br />
<h3>
Hypothesis</h3>
Reduced transient peak amplitude will cause loss of tactile impact and punch when played reasonably loud through loudspeakers.<br />
<br />
<h3>
Method</h3>
A music signal with very dynamic and transient content - mostly drums - is processed with a limiter to create peak limited test signals. <br />
Three different test signals were made - original, -3dB limited and -6dB limited. <br />
<br />
The original and the distorted signals are ABX-compared listening on headphones and on the big system. <br />
<br />
<i>Test signals</i><br />
<br />
<a href="http://2.bp.blogspot.com/-0C1Fa8LilzE/UzYZf_x1zlI/AAAAAAAAAK0/0BcCgLnMiFQ/s1600/limiter+test.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-0C1Fa8LilzE/UzYZf_x1zlI/AAAAAAAAAK0/0BcCgLnMiFQ/s1600/limiter+test.png" height="296" width="400" /> </a><br />
<br />
<br />
<h3>
Results</h3>
The less -3dB limited signal was difficult to distinguish from the original, and the difference was perceived as more noticeable when playing reasonably loud on loudspeakers. <br />
The difference was noticeable also on headphones, the limited signal seems slightly flatter sounding on the loudest drum hits. <br />
On loudspeakers there was a barely noticeable loss of physical transient impact. <br />
<br />
For the heavily -6dB limited signal differences could be verified as audible even when not playing very loud, there was distortion causing a reduction of clarity and perceived sound quality. <br />
On loudspeakers there was a clearly noticeable loss of physical impact. <br />
<br />
ABX results, headphones: <br />
Limited -3dB: Total: 8/10 (5.5%)<br />
Limited -6dB: Total: 10/10 (0.1%) <br />
<br />
ABX results, big system: <br />
Limited -3dB: ABX: 16/14/0.21%<br />
Limited -6dB: ABX: 10/10/0.1%<br />
<br />
<h3>
Conclusion</h3>
The results does not dismiss the hypothesis that peak transient amplitude is important for tactile impact and punch. <br />
<br />
The less -3dB limited signal was difficult to distinguish from the original. <br />
When looking at the waveforms the signals are clearly different, but when listening the differences are not so easy to detect reliably. <br />
Even the -6dB limited signal could pass unnoticed if there was no original reference to directly compare it against. <br />
Also, the reproduction equipment - mainly speakers - must be able to reproduce the transients without additional distortion. <br />
<br />
The combined results from this limiting test and the <a href="http://kvalsvoll.blogspot.no/2014/03/audibility-of-phase-distortion.html">phase distortion test</a> indicates that it is possible for such errors to be introduced unnoticed in the music production process - they simply can not hear it. <br />
<br />
The important part is that the severity of the transient distortion depends on how you listen. <br />
When sitting down to really enjoy your favourite music, you turn it up, and that is when the lack of life and dynamics is most apparent. <br />
<br />
Loud music production style utilizing heavy compression and limiting has several other negative effects on sound quality. <br />
The negative consequences of lost transient impact investigated here is only one part of the destruction. <br />
<br />
<h3>
</h3>
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-Ya05_uQqGxE/UzYZedpa_iI/AAAAAAAAAKs/Lyc1cEZGcXg/s1600/limiter+test+T138.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-Ya05_uQqGxE/UzYZedpa_iI/AAAAAAAAAKs/Lyc1cEZGcXg/s1600/limiter+test+T138.png" height="343" width="400" /></a></div>
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com3tag:blogger.com,1999:blog-7131957440381098047.post-85702053577400549432014-03-25T16:42:00.001+01:002014-03-25T16:42:46.395+01:00Audibility of phase distortion<br />
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>
Phase distortion at low frequencies causes audible degradation of music. <br />When is it audible, what causes it and how does it affect sound quality.
</i></span></b></span><br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-DGmec56pNAY/UzGfqAyJ6ZI/AAAAAAAAAJ4/1ZiYVocQVPI/s1600/fasetest+phase+distortion.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-DGmec56pNAY/UzGfqAyJ6ZI/AAAAAAAAAJ4/1ZiYVocQVPI/s1600/fasetest+phase+distortion.png" height="295" width="640" /></a></div>
<br />
<br />
<h3>
Intro</h3>
<br />
Phase distortion means that different tones gets a different time delay. <br />
It has been a general assumption that phase distortion in audio reproduction is not audible. <br />
<br />
Typical sources of phase distortion in audio reproduction are loudspeakers and room acoustics. <br />
<br />
Music can also be destroyed in the production process, where dynamic compression can cause effects similar to phase distortion. <br />
Dynamic compression in music is well known today as the Loudness War. <br />
The kind of signal processing used causes loss of transient peak amplitude, and smearing of the same transients over time, to compensate for the amplitude loss. <br />
It is this type of signal destruction that is investigated here. <br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-Wi9vMk8T-oo/UzGfxPynzzI/AAAAAAAAAKM/_etOJddwc0g/s1600/fasetest+q.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-Wi9vMk8T-oo/UzGfxPynzzI/AAAAAAAAAKM/_etOJddwc0g/s1600/fasetest+q.png" height="63" width="400" /></a></div>
<br />
Upon visual inspection one can see that the phase distorted waveform is clearly changed, and it may be difficult to understand why this is not also very easy to hear. <br />
But phase distortion means that the only change to the signal is related to timing, the spectral frequency distribution is the same, and there is no nonlinear distortion added. <br />
The energy of the signal is preserved, though very large phase shifts will cause the energy to be smeared out across a longer time interval. <br />
<br />
<br />
One thing that may be important is that the transient peak amplitude is reduced in level, and this is what is presented as a hypothesis for audible difference here. <br />
This reduction in peak level will potentially reduce the maximum peak sound pressure that is experienced. <br />
<br />
<br />
<h3>
Hypothesis</h3>
<br />
Reduced transient peak amplitude will cause loss of tactile impact and punch when played reasonably loud through loudspeakers. <br />
<br />
<br />
<h3>
Method</h3>
<br />
A music signal with very dynamic and transient content - mostly drums - is processed with an allpass-filter to create a phase shift that is large enough to change the signal so that the peak level is significantly reduced and the waveform is visually changed. <br />
Three different test signals were made - original, phase distorted, severely phase distorted by running all-pass twice. <br />
<br />
The original and the phase-distorted signal is ABX-compared by listening on headphones and on the big system. <br />
<br />
The big system is a full-range system with reasonably flat phase and group delay through most of the bass range.<br />
<br />
<i>Test signals: Original, 1x allpass, 2x allpass</i><br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-mtFEntDqZQU/UzGfuXfmjRI/AAAAAAAAAKE/HMbhk0ZvY5s/s1600/fasetest+allpass+org+1x+2x.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-mtFEntDqZQU/UzGfuXfmjRI/AAAAAAAAAKE/HMbhk0ZvY5s/s1600/fasetest+allpass+org+1x+2x.png" height="343" width="400" /></a></div>
<a href="http://2.bp.blogspot.com/-TANO1DifuH4/UzGf74EU0uI/AAAAAAAAAKc/FQVmQfEAWys/s1600/fasetest+T138.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"></a><br />
<br />
<h3>
Results</h3>
<br />
Listening on headphones, the phase distorted music could not be detected as different. <br />
Only when comparing to the severely phase distorted signal could a difference be verified, though now the differences were very clear as the distorted signal sounded more boomy and smeared in the bass. <br />
<br />
The phase distorted music signal could be verified as different from the original in the ABX-test, on the big system. <br />
The observed subjective differences are that the phase distorted signal lost some impact and punch. <br />
<br />
ABX results, headphones, allpass 2x: <br />
Total: 10/10 (0.1%) <br />
<br />
ABX results, big system, allpass: <br />
ABX: 16/14/0.21%<br />
<br />
<br />
<h3>
Conclusion</h3>
<br />
Phase distortion at low frequencies is audible and can cause a significant degradation of music, in certain specific situations, such as when listening on high quality loudspeaker systems at fairly loud levels. <br />
<br />
The results does not dismiss the hypothesis that peak transient amplitude is important for tactile impact and punch. <br />
<br />
In other situations, such as when listening on headphones, or at lower volumes or on lesser capable speakers, it was not possible to detect any audible difference between the phase distorted and original signal, as long as the added phase change and time delay is within reasonable limits. <br />
This also explains how it is possible that such errors are introduced in the music production process - they simply can not hear it. <br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-TANO1DifuH4/UzGf74EU0uI/AAAAAAAAAKc/FQVmQfEAWys/s1600/fasetest+T138.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-TANO1DifuH4/UzGf74EU0uI/AAAAAAAAAKc/FQVmQfEAWys/s1600/fasetest+T138.png" height="342" width="400" /></a></div>
<br />
<br />
<br />
<h3>
Next up</h3>
<br />
A similar test for peak limiting is coming up soon - is it audible, and how does it affect the sound.<br />
Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com4tag:blogger.com,1999:blog-7131957440381098047.post-61481962786177516442014-03-04T09:16:00.000+01:002014-03-07T06:00:19.131+01:002-channel with subwoofers set-up<br />
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>
I present the set-up of a 2-channel system, with simple subwoofer calibration. <br /><br />With measurements shown, so that we can see what is actually going on. <br /><br />And I will show how to try without measuring, only using a pink noise signal that can be played back from a file.
</i></span></b></span><br />
<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-phsO39frRGM/UxWE5BP-5vI/AAAAAAAAAJI/LH21dv8c4yE/s1600/pos+reloc.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-phsO39frRGM/UxWE5BP-5vI/AAAAAAAAAJI/LH21dv8c4yE/s1600/pos+reloc.jpg" height="480" width="640" /></a></div>
<br />
<br />
<br />
This is a standard 2-channel system with digital or analog source, controlled by an analog preamplifier. <br />
No DSP, no room correction, no bass management. <br />
The subwoofers have no digital processing, the only adjustments are level, crossover frequency (low-pass filter) and phase. <br />
<br />
The main speakers will play full range down to whatever frequencies they can output, there is no low bass cut-off. <br />
<br />
This configuration is what many enthusiasts actually will have for a 2-channel system. <br />
Now I will show that it is possible to integrate subwoofers into such a system with great success, even though there are limitations and compromises will have to be made. <br />
<br />
The addition of capable subwoofers transforms this system into full-frequency range with reference quality bass. <br />
<br />
This is a nice, smaller system, with satellite main speakers driven by a class-A amplifier with low output power. <br />
Max SPL is rather low, we hope for a nice and pleasant sound with a true three-dimensional presentation and great bass with precision, slam and capacity all the way down to far below hearing range. <br />
<br />
<br />
Summary of calibration adjustments:<br />
<ol>
<li>Placement not too far from the main speakers, but try to get positions with good gain and smooth response. </li>
<li>Adjust phase individually on subwoofers to get the best response of subs only. </li>
<li>Low crossover, 60Hz, max 80Hz. </li>
<li>Use RTA (Real-Time Analyzer) to see effects of adjustments in real-time. </li>
<li>Adjust crossover and level on subwoofers to get as close to your target response as possible. </li>
<li>While having the measurement gear out this is a good time to try alternative positions for the main speakers. </li>
</ol>
<br />
<br />
<h3>
Equipment</h3>
<br />
The important parts for this exercise are the main speakers, subwoofers and the room. <br />
Source and amplifier is not that important for set-up and calibration, as the process and measurements will be the same for any amplifiers without processing for crossover and delay. <br />
<br />
Room: <br />
3.6m width x 4.5m length. <br />
Door opening on right wall, large opening into other room through rear wall, window on left wall. <br />
Other room length 4.1m together with this room defines lowest length node at approximately 8.6m. <br />
Wood panel on all walls and ceiling, wood floor. <br />
Some chairs and a round table, media console for audio equipment. <br />
No additional acoustic treatment of significance. <br />
<br />
Low frequency response of this room is dominated by the total length of both rooms and the door opening acting as the port in a resonator where the room is the cabinet. <br />
This causes resonances from around 15Hz up to around 25Hz, where room response is strong. <br />
<br />
<br />
Main speakers: <br />
Small satellite system with 8" bass driver sealed, 2x 14cm mid, 1" dome HF. <br />
<br />
Subwoofers: <br />
2x small Compact Horn subwoofers with 10" driver (105dB/20Hz/2pi/1m, equals approx 12" ported or 15" sealed of high quality). <br />
<br />
Measurement instrumentation: <br />
REW measurement software, calibrated microphone, computer, USB I/O. <br />
<br />
<br />
<h3>
Initial placement</h3>
<br />
We start out with the system set up like this: <br />
<br />
<i>Room with L+R speakers and subwoofers initial placement</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-2TwcNJkNAMA/UxWE4g4JFwI/AAAAAAAAAI4/-vqTXrgO61c/s1600/pos+initial.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-2TwcNJkNAMA/UxWE4g4JFwI/AAAAAAAAAI4/-vqTXrgO61c/s1600/pos+initial.jpg" height="300" width="400" /></a></div>
<br />
<br />
We want 2 subwoofers to be able to get a reasonably smooth response. <br />
That also gives more output (+6dB), so that we can use smaller subwoofers, it is easier to place 2 smaller boxes compared to one giant monster. <br />
<br />
The subwoofer locations can be determined by measurement, either by measuring at the listening position (LP) while moving subwoofers, or by placing one subwoofer at the LP and then move around with the mic. <br />
Use the RTA in REW for this, run Pink PN Noise, then you can see the response in real-time while moving the mic around. <br />
<br />
The fact that we have no way to adjust for time differences between mains and subwoofers will limit placement options. <br />
Ideally the subs should be a little closer to the listening position (LP). <br />
Here we start out with a practical location that also works; in front of the main speakers, towards the corner. <br />
Bass is strong, and because the sound radiation is from the front of the subwoofer, it is radiating at some distance away from the corner, which usually gives a smoother response. <br />
In a set-up where the best sound quality is the goal, we do not want the main speakers in the corners, so this location is free to use. <br />
<br />
Placement of one subwoofer towards the rear of the room, behind the listening position, can also be an option. <br />
What will work in your room will depend on the acoustic properties of the room, as well as obvious practical considerations. <br />
<br />
<br />
<h3>
Initial measurements </h3>
<br />
We measure the main L and R speakers from the listening position (LP): <br />
<br />
<i>Frequency response L+R no subwoofers initial position</i><br />
<div class="separator" style="clear: both; text-align: center;">
<i><a href="http://3.bp.blogspot.com/-LOVmJTmLYpg/UxWE26IEUuI/AAAAAAAAAIY/nbgippllVQY/s1600/fr+l%252Br+initial.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-LOVmJTmLYpg/UxWE26IEUuI/AAAAAAAAAIY/nbgippllVQY/s1600/fr+l%252Br+initial.png" /></a></i></div>
<br />
<br />
And the 2 subwoofers: <br />
<br />
<br />
<i>Frequency response subwoofers before any adjustments</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-JSVBI9Z1U8A/UxWE3QPECXI/AAAAAAAAAIo/LV7a9OWWaYc/s1600/fr+sub+x2+initial.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-JSVBI9Z1U8A/UxWE3QPECXI/AAAAAAAAAIo/LV7a9OWWaYc/s1600/fr+sub+x2+initial.png" /></a></div>
<br />
<br />
<br />
<h3>
Sub phase adjustment </h3>
<br />
First the phase is adjusted on one of the subs to fill the response dip around 50Hz. <br />
For this particular room and sub locations this adjustment makes a large difference, but that may not be the case in a different room. <br />
Obviously, the room is not acoustically symmetric for both sub locations. <br />
Use RTA, adjust while monitoring the response in real-time. <br />
<br />
<i>RTA running for subwoofer phase adjustment</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-u_Wro5PHYzQ/UxWE5a4yQyI/AAAAAAAAAJQ/eUr07wIm7CA/s1600/rta+sub.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-u_Wro5PHYzQ/UxWE5a4yQyI/AAAAAAAAAJQ/eUr07wIm7CA/s1600/rta+sub.jpg" /></a></div>
<br />
<br />
<br />
<i>Frequency response subwoofers phase adjusted</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-vKVX9d9ArA0/UxWE55Dtl9I/AAAAAAAAAJY/wUMvuhJV6zM/s1600/fr+sub+x2+justert+fase.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-vKVX9d9ArA0/UxWE55Dtl9I/AAAAAAAAAJY/wUMvuhJV6zM/s1600/fr+sub+x2+justert+fase.png" /></a></div>
<br />
<br />
Then the phase on both subs are adjusted so that they fill in with the main speakers. <br />
Use RTA, watch how the response changes around the crossover frequency, adjust to max level. <br />
<br />
<i>Frequency response L+R+subwoofers initial position</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://4.bp.blogspot.com/-25TpSacRZjU/UxWE2w1QgiI/AAAAAAAAAIc/10YQr9v7ogo/s1600/fr+l%252Br%252Bsub+initial.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-25TpSacRZjU/UxWE2w1QgiI/AAAAAAAAAIc/10YQr9v7ogo/s1600/fr+l%252Br%252Bsub+initial.png" /></a></div>
<br />
<br />
<h3>
Sub level and crossover</h3>
<br />
Adjust to achieve a reasonable frequency response that extends the natural downwards tilt, and you may prefer some extra level at the lowest frequencies below 40-30Hz. <br />
Consider choosing a crossover rather low, below 80Hz or lower, to minimise effects from time alignment issues. <br />
Note that it may be necessary to adjust phase after changing the crossover. <br />
<br />
All this is best to do with the RTA, so that you can see the changes in real-time. <br />
<br />
<br />
<h3>
Adjustment without measuring </h3>
<br />
Using a pink noise signal and your ears to adjust phase, level and crossover for subs may at least give some improvement compared to no adjustment at all. <br />
<br />
Play a 200Hz bandwidth-limited pink noise signal from file. <br />
Adjust phase on one sub for loudest possible signal. <br />
Then adjust phase on both subs to get loudest level around the crossover frequency. <br />
This is the more difficult part, because is is not easy to know how the noise should sound when the setting is correct. <br />
Level and crossover is not easy to adjust using pink noise, because you would have a problem knowing how it should sound when everything is right, unless having a reference readily available to compare with. <br />
Headphones may be a solution - listen on headphones, then compare to how it sound on the system and adjust to same sound. <br />
It may be better to use some known music with bass, as actual music is more likely to reveal when something is way off, compared to a noise signal that still sound like what it is - noise. <br />
Obviously this is something that is not very easy to get right without measurement. <br />
The result depends heavily on the chosen program material and the listeners ability. <br />
<br />
Pink noise signal files can be downloaded from Kvålsvoll Design here: <br />
<br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%20100hz%201min.flac">Pink Noise 100Hz limited</a><br />
<a href="http://www.kvalsvoll.com/Articles/TestSignals/pn%201min.flac">Pink Noise full bandwidth </a><br />
<br />
<br />
<h3>
L+R position</h3>
<br />
Seems like the tilt is a bit too much down at higher frequencies, and it also sounds rather dark with recessed highs. <br />
In the midrange the response could be more flat, this is likely caused by boundary reflections from walls and floor around the speaker. <br />
So, we try to relocate the speakers a bit closer to the listening position, making the distance to the front wall larger. <br />
The larger distance between the speakers and the front wall also usually improves imaging and perceived clarity in the midrange. <br />
The speakers are also raised around 10cm to bring the tweeter on-axis. <br />
Angling is adjusted so that on-axis points exactly towards the listening position. <br />
<br />
<i>L+R speakers moved to new position closer to listening postion and raised</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-phsO39frRGM/UxWE5BP-5vI/AAAAAAAAAJI/LH21dv8c4yE/s1600/pos+reloc.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-phsO39frRGM/UxWE5BP-5vI/AAAAAAAAAJI/LH21dv8c4yE/s1600/pos+reloc.jpg" height="300" width="400" /></a></div>
<i><br /></i>
<br />
<br />
The response now looks much better in the midrange, and the tilt is reduced. <br />
<br />
<i>Frequency response L+R+subwoofers position adjusted</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/--5HSofKDLso/UxWE2xrB1XI/AAAAAAAAAIU/KDeOEcZdBJg/s1600/fr+l%252Br%252Bsub+justert+pos.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/--5HSofKDLso/UxWE2xrB1XI/AAAAAAAAAIU/KDeOEcZdBJg/s1600/fr+l%252Br%252Bsub+justert+pos.png" /></a></div>
<br />
<br />
<i>Frequency response L+R+subwoofers before and after position adjusted</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-3cCMeynjZ3c/UxWLM9HYhtI/AAAAAAAAAJo/9XJOMIlu8JA/s1600/fr+l+r+sub+justert+og+inital+pos.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-3cCMeynjZ3c/UxWLM9HYhtI/AAAAAAAAAJo/9XJOMIlu8JA/s1600/fr+l+r+sub+justert+og+inital+pos.png" /></a></div>
<br />
<br />
<br />
The impulse response is surprisingly good, especially considering the type of speaker and no acoustic treatment in the room. <br />
<br />
<i>Impulse response</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-zX3rVQ3rQkA/UxWE4cMg1yI/AAAAAAAAAJA/k9huA4vWsU4/s1600/ir.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-zX3rVQ3rQkA/UxWE4cMg1yI/AAAAAAAAAJA/k9huA4vWsU4/s1600/ir.png" /></a></div>
<br />
<br />
The step-response can be used to see if the subs are properly time aligned with the mains. <br />
Well, they are not, but that is not possible to correct when we have no delay adjustment on the mains. <br />
<br />
<br />
<i>Step response </i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-XXRmAMCIHHw/UxWE5ryBmzI/AAAAAAAAAJc/pBC0YrMX6Ig/s1600/sr.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-XXRmAMCIHHw/UxWE5ryBmzI/AAAAAAAAAJc/pBC0YrMX6Ig/s1600/sr.png" height="211" width="400" /></a></div>
<br />
<br />
The group delay also provides useful information about timing issues. <br />
If subs and mains are properly aligned they will end up in-line with the same average group delay in the area around the crossover. <br />
This can be difficult to see because this frequency range is usually affected by room and boundary reflections causing large group delay deviations. <br />
<br />
<i>Group delay</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://3.bp.blogspot.com/-_mxGWDMzl9Y/UxWE3r4zbxI/AAAAAAAAAIs/TRndspZXVS0/s1600/gd.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-_mxGWDMzl9Y/UxWE3r4zbxI/AAAAAAAAAIs/TRndspZXVS0/s1600/gd.png" height="216" width="400" /></a></div>
<br />
<br />
<br />
<h3>
Checking subwoofer capacity</h3>
<br />
We check the output and distortion of the subwoofers to see if it is likely that they can match the main speakers. <br />
<br />
<i>Distortion measurement sweep show 110dB at 20Hz with 1.7% THD</i><br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-F99E-vlK9V8/UxWEzfcPDEI/AAAAAAAAAIA/aNoQlDy6Yzw/s1600/dist+110db.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-F99E-vlK9V8/UxWEzfcPDEI/AAAAAAAAAIA/aNoQlDy6Yzw/s1600/dist+110db.png" /></a></div>
<br />
<br />
Indeed, the small Compact Horn subwoofers easily outperform the mains with 110dB at 20Hz with 1.7% distortion. <br />
They can obviously do a lot more, I did not bother to check, as that requires recalibration of the mic amplifier for more headroom. <br />
<br />
<br />
<h3>
How does it sound</h3>
<br />
The subwoofers seem well integrated, providing full-size bass with a heavy bottom, both impact and weight, dry and powerful. <br />
It does not get boomy or muddy in the bass even when the bass is running a little hot.<br />
<br />
The relocation of the mains further away from the front wall improved perception of depth and clarity in the lower midrange. <br />
<br />
The biggest problem is limited output capacity, it simply can not play loud. <br />
The bass range is not as smooth as one can experience from the best systems, and we know from the measurements that the response is not entirely flat. <br />
<br />
<br />
<h3>
Further improvements</h3>
<br />
The bass is quite heavy at the lowest frequencies, level is low around 50-70Hz, and there is a peak at 100Hz. <br />
This can possibly be improved by moving one or both subwoofers, and adjust subwoofer level and crossover. <br />
<br />
Since this set-up was done primarily for this article, I am satisified for now. <br />
If anyone in the neighbourhood wants to hear and experience this system please feel free to contact me.<br />
<br />
If you are interested in reading more on audio systems and set-up, check out my article <a href="http://www.kvalsvoll.com/Articles/HowtosetupaHomeTheaterSoundSystem.htm">How to Set-up a Home Theater System</a>. Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-33857233482345177782014-03-02T00:08:00.001+01:002014-03-02T00:08:28.960+01:00Floor reflection fixed<br />
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>Floor reflection fixed with two small interior add-ons</i></span></b></span><br />
<br />
<br />
<i>Puff ready for some music</i><br />
<i> </i><br />
<a href="http://1.bp.blogspot.com/-FoQH4im_HHQ/UxJc-CC3KTI/AAAAAAAAAHg/IB8tyJWn-34/s1600/puff+installert.jpg" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-FoQH4im_HHQ/UxJc-CC3KTI/AAAAAAAAAHg/IB8tyJWn-34/s1600/puff+installert.jpg" height="300" width="400" /></a>
<br />
<br />
<br />
When measuring speakers I have used cardboxes, carpets and such in front of speakers to dampen the first floor reflection. <br />
Useful both for indoor and outdoor measurements, this proves to at least have some effect on the reflection, improving measurement accuracy in a quick set-up. <br />
<br />
Now, could a similar approach be used in an ordinary room, and actually look nice and appear as a natural extension of the interior design. <br />
<br />
In The Moderate Cinema the main front speakers live in a very tight space, with lots of things around them, causing reflections that affect the response especially in the midrange. <br />
Normally, one does not treat the floor reflection, it also causes practical issues in most cases. <br />
However, in a room like this it may prove to be more practical to fix the floor reflection than trying to do effective damping and necessary relocation of other items. <br />
<br />
Initial experiments with card boxes covered with pillows and blankets show that this actually is a good idea, the frequency response is significantly improved.<br />
This can be made as a moderately sized puff, or footstool. <br />
<i><br />Frequency response initial testing - grey: bare floor, cyan: cardbox and pillows</i><br />
<br />
<a href="http://2.bp.blogspot.com/-wVm2qPeoOaw/UxJanBW-HQI/AAAAAAAAAGc/M5FJ-P2ydK0/s1600/fr+initial.png" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-wVm2qPeoOaw/UxJanBW-HQI/AAAAAAAAAGc/M5FJ-P2ydK0/s1600/fr+initial.png" height="212" width="400" /></a><br />
<br />
The completed design is a puff measuring 38x38x30cm, made of ordinary furniture foam covered with furniture fabric, and an optional matching blanket or pillow on top. <br />
Looks nice, is not too large, integrates well as part of the interior design. <br />
<br />
<br />
<i>Foam body for just the right acoustic absorption</i><br />
<br />
<a href="http://1.bp.blogspot.com/-ns3j1UEmM64/UxJcSSE5QwI/AAAAAAAAAGs/yhht3Q-96a8/s1600/skomgommi.jpg" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-ns3j1UEmM64/UxJcSSE5QwI/AAAAAAAAAGs/yhht3Q-96a8/s1600/skomgommi.jpg" height="300" width="400" /></a>
<br />
<br />
<br />
<i>Completed puff</i><br />
<a href="http://4.bp.blogspot.com/-XUWJ5YGEDCM/UxJcpeLiP2I/AAAAAAAAAG4/_dyXCuJDQmA/s1600/fr+ferdig.png" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><br /></a><a href="http://4.bp.blogspot.com/-PFERZ-t_7l4/UxJcn6TOYxI/AAAAAAAAAGw/sWq6H7dIcFs/s1600/puff.jpg" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-PFERZ-t_7l4/UxJcn6TOYxI/AAAAAAAAAGw/sWq6H7dIcFs/s1600/puff.jpg" height="300" width="400" /></a>
<br />
<br />
<br />
Carefully placed in front of each main front speaker, they significantly improve the frequency response and the impulse response in the midrange.<br />
<br />
A location somewhere around the middle between the speaker and the listening positon will often work good. In this room there is a table in the way and the best locations are somewhere rather close to the speakers. <br />
<br />
<br />
<i>Puff installed</i><br />
<br />
<a href="http://2.bp.blogspot.com/-Ynvi9-Ti2Co/UxJc8fh0HPI/AAAAAAAAAHc/hNo8IYY6S8c/s1600/puff+i+rom.jpg" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://2.bp.blogspot.com/-Ynvi9-Ti2Co/UxJc8fh0HPI/AAAAAAAAAHc/hNo8IYY6S8c/s1600/puff+i+rom.jpg" height="300" width="400" /></a>
<br />
<br />
<br />
<br />
<i>Frequency response shows reduction of peak 700Hz and dip at 400Hz in midrange</i><br />
<i> </i> <br />
<a href="http://4.bp.blogspot.com/-XUWJ5YGEDCM/UxJcpeLiP2I/AAAAAAAAAG8/epIS5onrxIA/s1600/fr+ferdig.png" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-XUWJ5YGEDCM/UxJcpeLiP2I/AAAAAAAAAG8/epIS5onrxIA/s1600/fr+ferdig.png" height="212" width="400" /></a>
<br />
<br />
<br />
<i>Filtered IR at 1000Hz also shows improvement </i><br />
<br />
<a href="http://1.bp.blogspot.com/-OyjRWztH2SY/UxJc2HNKI1I/AAAAAAAAAHM/LMYT-bqbyK0/s1600/ir+1000hz.png" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://1.bp.blogspot.com/-OyjRWztH2SY/UxJc2HNKI1I/AAAAAAAAAHM/LMYT-bqbyK0/s1600/ir+1000hz.png" height="212" width="400" /></a>
<br />
<br />
<br />
<i>The group delay shows reduced reflections in the midrange</i><br />
<br />
<a href="http://4.bp.blogspot.com/-YVhkcA77OPs/UxJcreapBAI/AAAAAAAAAHE/ng_Pye7tg3w/s1600/gd.png" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://4.bp.blogspot.com/-YVhkcA77OPs/UxJcreapBAI/AAAAAAAAAHE/ng_Pye7tg3w/s1600/gd.png" height="212" width="400" /></a>
<br />
<a href="http://2.bp.blogspot.com/-Ynvi9-Ti2Co/UxJc8fh0HPI/AAAAAAAAAHc/hNo8IYY6S8c/s1600/puff+i+rom.jpg" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><br /></a>
<br />
<a href="http://2.bp.blogspot.com/-Ynvi9-Ti2Co/UxJc8fh0HPI/AAAAAAAAAHc/hNo8IYY6S8c/s1600/puff+i+rom.jpg" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><br /></a>
<br />
<i>The full-range IR show no significant difference, not so strange due to the very controlled directivity of the loudspeakers at higher frequencies</i><br />
<br />
<a href="http://3.bp.blogspot.com/-AtMolG5ooYc/UxJmkIU42fI/AAAAAAAAAHw/Xmhz5sCdwbI/s1600/ir.png" imageanchor="1" style="margin-left: 0em; margin-right: 1em;"><img border="0" src="http://3.bp.blogspot.com/-AtMolG5ooYc/UxJmkIU42fI/AAAAAAAAAHw/Xmhz5sCdwbI/s1600/ir.png" height="212" width="400" /></a>
<br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-44369150479488912912014-01-14T06:36:00.000+01:002014-01-14T06:36:21.824+01:00New Loudspeaker Sound Pressure CalculatorI have added a new version of the Loudspeaker Calculator here, more convenient for simple one-speaker calculations:<br />
<br />
<a href="http://www.kvalsvoll.com/Articles/AudioCalculatorspl.htm">Calculator for Loudspeaker Sound Pressure Level </a><br />
<br />
The new calculator lets you see the sound pressure levels from a loudspeaker in a specified room, and it is easy to get an overview of the different parts of the sound - direct sound and reverberant field.<br />
<br />
The direct radiated SPL is the sound from the speaker with no room contribution, as in an acoustically dead space.
<br /><br />
The reverberant contribution is the sound contribution from all
reflections in the room.
The same simplified model from the <a href="http://www.kvalsvoll.com/Articles/AudioCalculators.htm">Calculator for Speaker Requirements</a> is used, it will be reasonably valid for small rooms
with normal dimensions.
Keep in mind that reverberant sound field behaviour in small rooms is
very frequency dependent, as you approach lower frequencies, around the
Schroeder frequency, the sound field will be dominated by discrete
reflections from and between boundaries.
<br /><br />The sum total SPL is the diffuse field sum of the direct and reverberant sound. Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-39279374163041392272013-11-14T21:21:00.001+01:002013-11-14T21:21:36.530+01:00Norwegian versionI will publish some of my posts and articles in <a href="http://kvalsvollnorsk.blogspot.no/">Norwegian here</a>.<br />
<br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-81778740982466625312013-11-13T03:48:00.002+01:002013-11-13T05:03:39.992+01:00How Loud is it - Sound pressure requirements for movies and music<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
<span style="color: #999999;"><b><span style="font-size: large;"><i>We see that dimensioning a sound reproduction system for at
least 120dB output capacity is reasonable and not overkill if realistic
sound is the goal. </i></span></b></span><br />
<br />
<br />
So, how loud is it. <br />
<br />
What kind of sound level exposure is to be expected, and what sound pressure level should be used for system requirements. <br />
<br />
I did some measurements while playing music and movies, to show exactly how loud it is, at a reasonably loud level, and a little bit louder. This information can then be used to find requirements for loudspeakers, and also give a better understanding of why sound quality often is compromised. <br />
<br />
All measurements are done on a calibrated system. Using the -20dB RMS pink noise method and verified on frequency response measurements the calibration accuracy is within +-0.5dB, -20dB RMS equals 85dB from each main front speaker, 0dB peak level equals 105dB peak SPL. <br />
<br />
First, some music. <br />
<br />
Played at 0dB, we can see the RMS sound pressure level varies from 75dB to 95dB, while peak levels approach 113dB. Not perceived as very loud, most will find it this to be a pleasant volume, and the bass has some physical impact and realism.<br />
<br />
At around time 02:30 level is increased to +8dB, and now it is quite loud, with RMS level above 100dB, and we can observe peak levels above 120dB. <br />
<br />
<i>Music playback at 0dB and +8dB, good recording</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-vq2iFfGlpyg/UoLfq9xMozI/AAAAAAAAAE8/G8nl4bkTuNI/s1600/sheffieldlabs_ruffjam_0db_+8db.png" imageanchor="1" style="clear: none; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="436" src="http://1.bp.blogspot.com/-vq2iFfGlpyg/UoLfq9xMozI/AAAAAAAAAE8/G8nl4bkTuNI/s640/sheffieldlabs_ruffjam_0db_+8db.png" width="640" /></a></div>
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<br />
Another example, showing some of the problems with reduced sound quality in most newer recordings. <br />
<br />
First a good old one, then a newer from 2009, same artist, all played at 0dB. <br />
<br />
We see that the peak levels are the same, but the new recording is more compressed and has a louder RMS level, about 5dB higher. This higher RMS level means it is required to turn it down 5dB to maintain the same loudness, the problem then is of source that the peaks are also reduced by 5dB, and all the punch and impact and realism is gone. <br />
<br />
This recording shows the same peak level as the first example, around 113dB. <br />
<br />
<i>Music - old and new, 0dB</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://1.bp.blogspot.com/-eSjHS5LsHJc/UoLfuk_AMTI/AAAAAAAAAFI/ecqmdSUJw0A/s1600/musikk_gammeloggod_ny2009_0db.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="435" src="http://1.bp.blogspot.com/-eSjHS5LsHJc/UoLfuk_AMTI/AAAAAAAAAFI/ecqmdSUJw0A/s640/musikk_gammeloggod_ny2009_0db.png" width="640" /></a></div>
<br />
<br />
The difference between the peak and RMS level is sometimes referred to as the "crest factor", a number that tells us something about how dynamic a piece of music is. Good recordings often have a crest factor of 20dB or more, while new popular music can have less than 10dB. <br />
<br />
The music examples analyzed here tells us that loudspeakers must be dimensioned for at least 113dB if we want to play music at around 90-95dB sound pressure level, and if we want to play loud, more than 120dB can easily be required.<br />
<br />
It is only peaks and transients of very short duration that reach those maximum levels, but the reproduction system must be dimensioned to be able to reproduce those peaks, or else the quality of the sound reproduction will be compromised. If the loudspeakers are not able to handle the peaks it will first start to sound more flat and the physical impact of drums and sound effects will be missing, and if you turn it up even further, it will start to sound bad due to distortion. <br />
<br />
Note that the black RMS lines in the graphs is SPL-dB(Z), meaning full-bandwidth measurements, actual sound level exposure for comparison to noise level standards are much lower when C or A frequency weighting is used. <br />
<br />
Now, a movie.<br />
<br />
Master & Commander, DVD-version with the best sound, the cannon scene in the middle of the film. Here we see that the cannons peak out far above 120dB (124dB peak), but the RMS level is mostly at 80-95dB. This scene, played at 0dB as shown here, is not excessively loud, but the experience is realistic and powerful. <br />
<br />
<i>Movie at 0dB, Master & Commander action scene</i><br />
<div class="separator" style="clear: both; text-align: center;">
<a href="http://2.bp.blogspot.com/-2pfSrfZdUNQ/UoLfxkAoNII/AAAAAAAAAFQ/WrTWrry4PTc/s1600/film_0db_mic132dbcal.png" imageanchor="1" style="clear: left; float: left; margin-bottom: 1em; margin-right: 1em;"><img border="0" height="435" src="http://2.bp.blogspot.com/-2pfSrfZdUNQ/UoLfxkAoNII/AAAAAAAAAFQ/WrTWrry4PTc/s640/film_0db_mic132dbcal.png" width="640" /></a></div>
<br />
<br />
The conclusion is that for realistic sound reproduction of music and movies it is required to have output capacity well above the average listening level, at least 20dB more for most good source material. The requirements given in the article <a href="http://www.kvalsvoll.com/Articles/HowtosetupaHomeTheaterSoundSystem.htm" target="_blank">How to set up a Home Theater Sound System</a>, and numbers that can be found using the <a href="http://www.kvalsvoll.com/Articles/AudioCalculators.htm" target="_blank">Audio Calculator</a> are realistic and valid requirements, and dimensioning for less capacity will lead to compromised sound reproduction.<br />
<br />
This also gives us some clues for reasons why many claim it sounds "too loud" playing a move at 0dB, because the speakers may not be properly dimensioned and will distort the sound, and distorted sound is perceived to be "too loud". <br />
<br />
Other factors that affect perceived loudness is amount of early reflections and reverberation. <br />
The room needs to have acoustic properties suitable for sound reproduction for higher sound levels to be experienced as pleasant and not too loud.<br />
<br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-42760366524937828812013-07-19T00:14:00.001+02:002013-07-29T16:11:01.103+02:00Audio Calculator for Speaker RequirementsI have now completed the first version of the <a href="http://www.kvalsvoll.com/Articles/AudioCalculators.htm">Calculator for Speaker Requirements</a>, for home theater and sound reproduction. <br />
<br />
By entering data for room and speakers, the sound pressure level can be estimated to verify if the speaker configuration has sufficient output to meet the chosen required listening level. <br />
<br />
A graphical presentation shows the current status, and provides point and click access to each speaker configuration section. <br />
Speakers that do not meet requirements are indicated, it is easy to get an overiew of the current situation. <br />
<br />
<i>Speaker Calculator status image</i><br />
<a href="http://2.bp.blogspot.com/-OeuGjDhNA0s/Uehmo8IHN4I/AAAAAAAAAEU/TTImei6f0fY/s1600/flottbilde.png" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="295" src="http://2.bp.blogspot.com/-OeuGjDhNA0s/Uehmo8IHN4I/AAAAAAAAAEU/TTImei6f0fY/s320/flottbilde.png" width="320" /></a><br />
<br />
<br />
<br />
<br />
The most difficult part was to decide how to calculate the reverberant sound field contribution - the sound that is added by the room itself. <br />
The chosen method is approximately valid for relatively small rooms that are acoustically well damped, with reasonably normal height-length-width relationship. <br />
For larger spaces or odd room shapes the model may be less accurate. <br />
<br />
With this tool it is quite straight-forward to check whether a chosen speaker set will be usable, and also see how much amplifier power is needed. <br />
<br />
This is very useful for subwoofer configuration - add or remove different subwoofers and see the results immediately. <br />
<br />
It is easy to see that the most difficult requirement is the subwoofer. <br />
Reference level with a nice house-curve lift at the lowest frequencies will require massive output capability, most likely several powerful subwoofers must be used. <br />
<br />
Tooltip provides additional information for many of the different data items. <br />
<br />
<h3>
Master Volume Listening Level</h3>
The loudest listening level is selected, this forms the foundation for the rest of the requirements.<br />
<br />
Level can be chosen from a set of predefined values. <br />
There is a reason for not using just a number to be entered - the range of values now reflect the level of accuracy one can expect, there are also descriptions for the different levels, and steps of 3 - 6 - 10dB are appropriate, as these levels provide suitable steps in loudness to span the range from reference (quite loud) to a lower -20dB.<br />
<br />
Now, these are meant to be the systems maxiumum design requirement - that does of course not mean that one always must listen at these volumes. <br />
Even -20dB may be too loud sometimes, and for quiet movie or documentary both the dialogue and sound effects should be clear and easy to understand at, say, -40dB. <br />
But you don't dimension the home theater for that. <br />
<br />
<h3>
Room data</h3>
Dimensions and acoustic data for the room is used to calculate the resulting sound. <br />
<br />
Here the reverberation time T60 may cause some uncertainty, regarding what value should be entered. <br />
If the theater has not been built yet, how can you measure it. <br />
The answer is, you do not need to measure it, you determine the value instead, and thereafter fix the room with acoustic treatments to reach that value. <br />
<br />
A T60 around 0.25 or lower is nice for the smallest rooms, 40-60m3, or 12-20m2. <br />
Larger rooms have longer reverberation, 0.3 and up to 0.4 can still be usable for rooms up to 40-60m2. <br />
<br />
<h3>
Speakers and room </h3>
Distance from listening position to speakers determines how much attenuation there is in the direct sound. <br />
<br />
Speaker directivity is the radiation pattern of the speaker: <br />
1: Omnidirectional 4π radiating. Subwoofer or normal speaker at low frequencies. <br />
2: 2π radiating. Recommended for wide dispersion surrounds (180°). <br />
3: Dipole, and normal radiating. Recommended for mains L,R with low directivity - direct radiating mid and tweeter. <br />
4: 45° radiating. Recommended for mains L,R with higher directivity - horns, waveguides. <br />
<br />
The critical distance, calculated based on room data and speaker directivity, is displayed. <br />
This is the distance where the reverberant field and the direct radiated sound are equally loud. <br />
Beyond this distance, the sound from reflections around in the room will be louder than the sound that comes directly from the speaker. <br />
<br />
<h3>
Subwoofer configuration</h3>
Defines how to calculate subwoofer sound pressure level. <br />
When main and surround speakers are set to Small - routing the sub frequencies to the subwoofer, the required capacity for the sub must include the added signals. <br />
<br />
House curve means a customized frequency response target with a boost at the very low end, starting typically at around 50-100hz, full level at 20Hz. <br />
Clearly this will also add to the required spl form the subwoofers. <br />
<br />
Since the main and surround channels are very unlikely to have full level low-frequency content, the level of contribution can be adjusted. <br />
<br />
Loss means correction from 1m/2&pi; specification to in-room at listening position. <br />
The actual correction will vary according to room construction and size, and subwoofer location. <br />
A range of typical values can be selected, and when set to "Use distance" the spl is calculated using reverberant field and room data. <br />
<br />
<h3>
Speaker Requirements</h3>
Sensitivity for the speakers must be specified, as measured at 1m with 2.83V. <br />
Often specified as dB SPL/1m/1W, as 2.83V equals 1W into 8 ohm load. <br />
Some speakers are 4 ohm, and in some cases sensitivity is given for 1W into 4 ohm, then add 3 dB and you have the sensitivity for 2.83V. <br />
<br />
Actual SPL at listening position is calculated using the entered Actual Power. <br />
The Power calculated is the required power to reach the required spl. <br />
<br />
<h3>
Subwoofer</h3>
Four different subwoofer types can be selected, in any reasonable number. <br />
The configuration table allows for quick and easy overview of different subwoofer configurations. <br />
<br />
For subwoofer specification, the maximum spl at 20Hz, measured at 1m distance 2π (groundplane) must be used. <br />
Make sure the value you use is a real, measured value, and not some marketing number. <br />
Most subwoofers will be a lot more powerful at higher frequencies, like 60Hz, than at the lowest 20Hz and below, so be aware of getting the right spl number, you want the one for 20Hz. <br />
If the specification is for 2m groundplane, just add 6dB to that value to get the 1m/2π. <br />
<br />
<h3>
For existing and new installations</h3>
The calculator is useful both for new and existing installations. <br />
Due to flexibility in what data may be entered, there will always be a way to get approximate information about performance. Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-7812797438034066762013-07-01T05:13:00.000+02:002013-07-01T05:13:08.718+02:00More on Compact Subwoofer TechnologyThe Compact Subwoofer Technology is a design method for small horn subwoofers, presented in the <a href="http://www.kvalsvoll.com/Articles/CompactSubwooferTechnology.htm" target="_blank">article available on the Kvålsvoll Design web pages</a>. <br />
The article describes briefly what it is, and how it works, read the entire article there, it is also available for <a href="http://www.kvalsvoll.com/Articles/CompactSubwooferTechnology.pdf" target="_blank">download as .pdf</a> file. <br />
<br />
Now I will discuss some of the more practical implications of the small horn<br />
designs, and give some examples on what can be achieved, in real subwoofers. <br />
<br />
Several subwoofers have been designed, and some of those have been built and<br />
tested. <br />
<br />
The very small 6-14 subwoofer was designed to be compact, at the expense of<br />
low frequency output capacity. Design specification, output capability: 30Hz,<br />
100dB (1m/2pi). <br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="http://2.bp.blogspot.com/-h72Ao4TDUcE/UdDi7aDPJ3I/AAAAAAAAAD8/v7RQxbV3Sg8/s480/MicroSub+6-14+4.jpg" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="235" src="http://2.bp.blogspot.com/-h72Ao4TDUcE/UdDi7aDPJ3I/AAAAAAAAAD8/v7RQxbV3Sg8/s320/MicroSub+6-14+4.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The 6.14 subwoofer. A very compact 30Hz, 100dB design.</td></tr>
</tbody></table>
<br />
This means it is not a real, full bandwidth subwoofer, and can not play powerful<br />
bass in a larger or even medium sized room with the physical authority and feel that larger systems have. <br />
However, the small size have some advantages, and the output is enough for low and mid volume tv or movie, and music. <br />
With two of them in a small room they played loud enough to have a gentle physical impact on the cannons in the Master & Commander movie. <br />
Being small and nice looking, it is easy to find a place for them, they will also often fit under a sofa. <br />
Another advantage of small size is that they are easier to move around for measurements and testing. <br />
<br />
Utilizing a small 6.5" driver, this design really pushes the limit for output from such a small woofer. <br />
<br />
30Hz extension is not enough to get the solid weight of low frequency effects in movies, and nowadays there are lots of music that also benefit from extension down to below 20Hz. <br />
The difference really has to be experienced.<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="http://3.bp.blogspot.com/-pT5d1pLCZ2I/UdDjD4uXa6I/AAAAAAAAAEI/71divLj5quA/s708/MicroHorn+og+MicroSub+6-14.jpg" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="http://3.bp.blogspot.com/-pT5d1pLCZ2I/UdDjD4uXa6I/AAAAAAAAAEI/71divLj5quA/s1600/MicroHorn+og+MicroSub+6-14.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The T138 (left) is a real subwoofer with true 20Hz capacity. As we can see, it comes with a price.</td></tr>
</tbody></table>
<br />
<br />
Now, compare the size of the 6-14 to the T138. This is a real subwoofer.<br />
Extension to well below 20Hz, design output 112dB/1m/2pi at 20Hz. <br />
<br />
Small is a relative term. <br />
Even though the compact subwoofer technology enables very good performance for the size, it still can not beat the physics of low frequency sound reproduction. <br />
More output at lower frequencies will still require a larger box.<br />
<br />
<h4>
SPL requirements</h4>
How much output does one need, then. <br />
Let us assume movie playback at reference level on a calibrated system, we can calculate the theoretical maximum sound pressure level from the subwoofers, when bass management routes all LF to the sub, including LFE track:<br />
<br />
<table border="0" cellspacing="0" cols="4" frame="VOID" rules="NONE">
<colgroup><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17" width="86"><b>Source</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL ref (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>N</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>Sum N (dB)</b></td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">L</td>
<td align="RIGHT" bgcolor="#94BD5E">105</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">105</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">R</td>
<td align="RIGHT" bgcolor="#94BD5E">105</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">105</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">C</td>
<td align="RIGHT" bgcolor="#94BD5E">105</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">105</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">SL</td>
<td align="RIGHT" bgcolor="#94BD5E">102</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">102</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">SR</td>
<td align="RIGHT" bgcolor="#94BD5E">102</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">102</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">RL</td>
<td align="RIGHT" bgcolor="#94BD5E">102</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">102</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">RR</td>
<td align="RIGHT" bgcolor="#94BD5E">102</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">102</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">LFE</td>
<td align="RIGHT" bgcolor="#94BD5E">115</td>
<td align="RIGHT" bgcolor="#94BD5E">1</td>
<td align="RIGHT">115</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17">Sum SPL (dB)</td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="RIGHT" bgcolor="#FF3333">124.079116</td>
</tr>
</tbody>
</table>
<br />
We see that maximum sub output may actually be 124dB. <br />
However, we can make some assumptions that lowers this number considerably. <br />
First, it is unlikely that there is full level content at 20Hz and below. <br />
And, if there are any other sounds playing at the same time in the front and surround channels, some of the headroom is used for that signal, and thus can not have low output at maximum. <br />
For most of the time, we can assume it may not be necessary having more than 115dB capability. <br />
<br />
But, since we would like to have some reserve headroom for a nice house-curve with some boost down at the lowest frequencies, that must be added. <br />
Let us assume +6dB. <br />
We still end up with 115dB + 6dB = 121dB. <br />
<br />
To achieve this kind of output will require some powerful subwoofers. <br />
We need the real thing.<br />
<br />
<h4>
4 decent subwoofers is no overkill..</h4>
Simulations of the S4 subwoofer, a nice, 62l net volume/97l external design, shows output capability at 108dB/20Hz/1m. <br />
Around half the size of the T138 pictured above. <br />
Now, assuming we loose 3dB on average in-room from the 1m output to th listening position, we see that 4 of these subwoofers can give us 117dB:<br />
<br />
<br />
<table border="0" cellspacing="0" cols="6" frame="VOID" rules="NONE">
<colgroup><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17" width="86"><b>Source</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL ref (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>N</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>Sum N (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL diff LP1 (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL LP1 (dB)</b></td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">S4</td>
<td align="RIGHT" bgcolor="#94BD5E">108</td>
<td align="RIGHT" bgcolor="#94BD5E">4</td>
<td align="RIGHT">120.0412</td>
<td align="RIGHT">-3</td>
<td align="RIGHT">117.0412</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT" bgcolor="#94BD5E">0</td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT" bgcolor="#94BD5E">0</td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17">Sum SPL (dB)</td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="RIGHT" bgcolor="#FF3333">120.0412</td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="RIGHT" bgcolor="#FF3333">117.0412</td>
</tr>
</tbody>
</table>
<br />
Also consider that the output increases some up in the mid-bass range. <br />
This should be a good start for a nice subwoofer setup.<br />
<br />
<h4>
Advantage of small horn - the compact subwoofer technology</h4>
To achieve the same output with sealed box subwoofers would require more subwoofers, and a lot more power: <br />
<br />
<table border="0" cellspacing="0" cols="6" frame="VOID" rules="NONE">
<colgroup><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col><col width="86"></col></colgroup>
<tbody>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17" width="86"><b>Source</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL ref (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>N</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>Sum N (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL diff LP1 (dB)</b></td>
<td align="LEFT" bgcolor="#CCCCCC" width="86"><b>SPL LP1 (dB)</b></td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17">Sealed 50l</td>
<td align="RIGHT" bgcolor="#94BD5E">100</td>
<td align="RIGHT" bgcolor="#94BD5E">10</td>
<td align="RIGHT">120</td>
<td align="RIGHT">-3</td>
<td align="RIGHT">117</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT" bgcolor="#94BD5E">0</td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT" bgcolor="#94BD5E">0</td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#94BD5E" height="17"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="LEFT" bgcolor="#94BD5E"><br /></td>
<td align="RIGHT">0</td>
<td align="LEFT"><br /></td>
<td align="RIGHT">0</td>
</tr>
<tr>
<td align="LEFT" bgcolor="#CCCCCC" height="17">Sum SPL (dB)</td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="RIGHT" bgcolor="#FF3333">120</td>
<td align="LEFT" bgcolor="#CCCCCC"><br /></td>
<td align="RIGHT" bgcolor="#FF3333">117</td>
</tr>
</tbody>
</table>
<br />We see that using a driver with similar parameters in sealed boxes requires 10 subwoofers, and that is not really practical. <br />(For sealed simulation: mms increased to 2x, mounted in 50l sealed enclosure, driven at same voltage level, excursion xmax = 16.8mm). <br /><br />An alternative could be to use larger vented boxes, but bigger boxes are more difficult to place, likely it is easier to find space for four smaller boxes than one or two monster-cabinets. <br />There is another advantage to using several smaller subwoofers as well - when located spread around the room they tend to even out the frequency response. <br />But that is a different subject on its own, so we can get back to that later some time. <br />
<br />
<br />
<br />Anonymoushttp://www.blogger.com/profile/15829124437761779916noreply@blogger.com0tag:blogger.com,1999:blog-7131957440381098047.post-22301078214858542962013-06-28T00:42:00.001+02:002013-06-28T07:10:53.706+02:00Audio, design, the making of thingsHere I will present articles and notes about things I make, new technology, new designs.<br />
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The content will be related to audio design and technology, control systems and cybernetics, and design - the making of things. <br />
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My <a href="http://www.kvalsvoll.com/">Kvålsvoll Design company web page www.kvalsvoll.com</a> is now updated, and will continue to receive new articles and designs.<br />
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I will release some audio related articles here as well, and you will be welcome to join in and comment on those.<br />
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