# Membrane or Resistive?



## Chuck27 (Feb 27, 2011)

First post from a new member who was introduced to the forum through the use of REW.

I'm really just getting started on the acoustics in my dedicated theater room. I have a BG Radia BGX-4850 sub system that will eventually go in the ceiling, at present the modules are laid out on the floor while I experiment with position to get the best response.

I have done a lot of reading about bass traps for the corners and I have a question that I have not seen answered elsewhere: Membrane traps or resistive traps in the corners? I see a lot of discussion surrounding filling the corners with resistive material, yet if the corners are where P=Max and V=min, would a membrane absorber, or series thereof in different thicknesses, be more effective? I was thinking of a membrane absorber in each corner, with the front surface stepped to support 1/4, 1/2 and 3/4 thick plywood panels with a flush front.

Thoughts or opinions?

Thank you,

Chuck


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## bpape (Sep 14, 2006)

A THIN membrane could work OK. The problem is that ALL frequencies build up in corners and dedicated membrane type absorbers are relatively narrow in nature so you'd be ignoring a lot of the frequency band.

There are other places where membranes can be used effectively besides the corners.

The thinner the membrane, the less it's going to reflect in terms of something like 703 or mineral wool with just a facing on it as opposed to something like 1/4" plywood.

Bryan


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## Chuck27 (Feb 27, 2011)

Thank you for that, Bryan. I had neglected to consider that of course more than just sub-300 Hz frequencies would collect in the corners and I see now why larger resistive absorbers are more popular. And you are certainly right that there are easier locations to put a membrane absorber than in a corner!

I have learned a great deal just in the few days I have been lurking in this forum.

Since I'm starting from a semi-clean slate, I think I will (a) get my subwoofer modules where they need to be for the smoothest response, (b) finish the insulation-stuffed faux ceiling that hides the subwoofer modules, (c) fill the vertical corners with resistive material, and then start doing RTAs to determine what else I need to fix.

I am fortunate that in exchange for surrendering decorating rights to the rest of the house, I have been granted free reign in the basement to build a theater the way I want.

Thanks again,

Chuck


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