The membrane isn't tuned. It's reactive over its whole area, so the more area you cover the better. Also, the panels should be joined so the area covered is the sum of the panel areas rather than a smaller area per panel.Use thin strand board if you can get it. Use dampening material on the wall behind the panels and on the face and you'll get better LF and HF absorption.

Thanks for the answer.But this way I can't really say how much frequency I'm about to absorb. For example if you use too much dampening material on the front (let's say having membranes all around your room) I could get in trouble loosing too much HF, right? You could measure it but I don't have access to a measurement system unfortunately. I'm just calculating it with the help of the materials degree of absorbtion. Maybe there is a table for OSB absorbtion degrees? So then I would know how much frequency I killed with for example a 10 square meter 15mm OSB board. Or am I thinking the wrong way?

I'm about to install absorbers into our new studios naked control room and came across the info on membrane absorbers (http://www.electricalaudio.com/StudioA/membrane.php) used in Alcatratz and Control Room A. I'm looking for an alternative to traditional bass traps. Are these really just OSB boards hung on the ceiling? At which frequency range do they work? Do you have to use special OSB material? Is there a special amount of air volume needed behind the membrane? Of course we don't have as much room space available in our control room as at Electrical so I'm curious about this method using OSB boards. Maybe we can save some of the room space?

Yeah, if I'm making a room dead I want it dead-ass dead, so I don't care if I have "too much" HF absorption. I don't really have any advice on sculpting the response of the room selectively.

I'm no expert but I think that a heavy damping material hung from the ceiling will have a pretty low resonance frequency, the more the material is distanced from the wall, the lower the reso frequency will be. Anything below that frequency will cut through, but because of the density of the material and it's distance from the wall, I'm skeptic that alot of low frequency content will reflect back into the room. More than that, see how much material the sound waves have to get through until they get to the OXB, a lot of the low frequency material will be absorbed by the inner walls themselves(I think).The high frequencies will be absorbed by all the fabric in the room, they never get through the walls to the membranes.

You can place slotted or perfed masonite (pegboard) in front of a standard corner trap and it will be nearly as functional as the traditional bass trap.With each corner trap placed, you will also eliminate one of the right-angle corners, instead trading it for two 45 degree intersections.

Thanks for the advice anyway. I looked on the internet but didn't find the absorbtion degree of OSB. In the book I have they have a table where you can see how much frequency is absorbed by for example a bass trap with a depth of let's say 60cm. This way you can find the right absorbers for your room, just by calculating (if you want a flat frequency response). Surely if you just want it dead then you're not about to calculate it, you just make it dead no matter what the frequency response says.

Yep, that's probably true if you build it just like in Alcatraz. But I'm unfortunately far away from duplicating this set up in our studio since I don't have enough space. I just thought of hanging up two or three big OXB boards (instead of bass traps) at the back wall and put a light cloth in front of it. That would have been easier then building a normal bass trap if it would have the same effect. Maybe it has! But it's hard to compare... The thing is that I know of the bass traps how much HF they absorb and so I know when it's too much of them cause I don't want to loose those HF.