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In Reply to: RE: DIY acoustic panels questions posted by temporarymadness@aol.com on February 06, 2008 at 17:46:11
You get more absorption with the panel spaced off the wall and one of the reasons for that is that you expose a second surface for absorption. If you make it reflective, you lose some absorption efficiency at those frequencies where the rear surface is reflective.
Of course, if you only want the amount of absorption you get from the front of the panel it won't matter as far as absorption goes but the reflectivity at high frequencies coupled with the fact that it will still absorb at lower frequencies may create a problem with the tonal balance of the reflected sound field. Note that I said "may create", not will create, since that HF reflectivity has to be considered in the context of the overall reflectivity/absorption spectrum of your room.
David Aiken
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