Sunday, March 2, 2014

Floor reflection fixed

Floor reflection fixed with two small interior add-ons

Puff ready for some music

When measuring speakers I have used cardboxes, carpets and such in front of speakers to dampen the first floor reflection.
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.

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.

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.
Normally, one does not treat the floor reflection, it also causes practical issues in most cases.
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.

Initial experiments with card boxes covered with pillows and blankets show that this actually is a good idea, the frequency response is significantly improved.
This can be made as a moderately sized puff, or footstool.

Frequency response initial testing - grey: bare floor, cyan: cardbox and pillows

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.
Looks nice, is not too large, integrates well as part of the interior design.

Foam body for just the right acoustic absorption

Completed puff

Carefully placed in front of each main front speaker, they significantly improve the frequency response and the impulse response in the midrange.

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. 

Puff installed

Frequency response shows reduction of peak 700Hz and dip at 400Hz in midrange

Filtered IR at 1000Hz also shows improvement 

The group delay shows reduced reflections in the midrange

The full-range IR show no significant difference, not so strange due to the very controlled directivity of the loudspeakers at higher frequencies

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