Feel free to ask questions. I'll do my best to answer.

Monday, December 27, 2010

Room treatment advice--quick and dirty

Controlling bass is difficult in a small room and likely the #1 priority of room treatment.

In general: for typical box speakers you want to absorb the whole front wall(the one behind the speakers or you depending on the situation) with something thick like 4" thick or so.  The further away from the wall, the better it will absorb lower into the bass range.  Bass trapping the front corners with broadband absorption would go right along with this.  This will reduce Speaker Boundary Interference Response(SBIR), reduce coloration and improve imaging.  The next absorption point would be your first ipsilateral reflection and can be done with 2 inches of absorption material.  4 inches is probably better and space it a few inches off the wall.  If your speaker have good off axis performance, this is optional depending on your desired effect.  That can help reduce high frequency hash and harshness caused by diffraction as well as squash polar anomalies.  That said, unmitigated early horizontal reflections have been shown to be "preferred" in blind tests.  They will increase your apparent source width and can arguably be detrimental to pinpoint imaging.

Then the rear wall with the thick stuff for more bass reduction, but diffusion can be used if your bass is well behaved.  Some people will also recommend absorbing the first reflection from the ceiling--others would say diffuse it.  Diffusion makes sense because the ceiling height is high enough to allow it to work.  The side walls can benefit from diffusion to improve spaciousness and sense of envelopment.  Diffusion has to be thicker than absorption to be effective to as low of a frequency and it can be expensive.  I would generally recommend broadband absorption midway between you and the speaker(or microphone as the case may be) to absorb the floor reflection--like a think foam pseudo-coffee table I use with stand mounted speakers.  Measurements of the coffee table found here.

If building new construction or if you are willing to modify the existing structure, making you walls into resonating diaphragm absorber makes better sense for controlling low frequencies because the areas of highest pressure are right next to the walls. Porous traps reduce particle velocity and best used away from walls for bass frequencies.

I will continue update this when I have time/desire.

More Rationale
Further Reading
Boundary Issues

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