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Hello Audiophiles! My name is James - I've been working with a talented and insightful acoustic designer and together we've come up with an idea for a membrane corner bass trap. I'm including 3 graphics of the concept, and would be very interested in your feedback. Here's the idea...

- The trap stands 4' tall, about 2'6" wide and stick out about 2'6" from the back wall. The back is open to the room corner. I intend to stack 2 (8' high) in 2 of my 4 corners - other 2 corners are too small with windows and doors in the way and will receive a more generic treatment.

- At the front we plan to use 4" thickness of mineral wool - 2" of 6lbs/ft3 at the very front, backed with 2" of 2.5lb/ft3. We feel the variation of density may tend to cut back on the natural resonance of the panels, small as that resonance may be.

- Behind this is a 1.5" air space, followed by a mass loaded vinyl membrane hanging free from a top bar. It is about 2'5" wide and 48" high.

- Then another 1.5" airspace followed by the same mineral wool treatment as on the front of the trap, with the 2.5lg/ft3 on the inside , followed by the 6lb/ft3 at the very back, then there's an open back into the corner of the room, and we may loose pack insulation between there and the room corner.

Can't wait for your input! James
 

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seems some of the most effective products from RealTraps, GIK and possibly ASC all use the membrane - also an interesting video on youtube of guys from sound-on sound mag constructing a big bass trap in a vocal booth. The big question is, some folks put the membrane at the front with the 703 or such behind - I imagine some high freq reflections off the membrane back into the room with this scenario. Others put the membrane behind the 703 - maybe for mid and high absorption. Or maybe there are other implications to which order they are in, like Q or just plain bass sucking power.
 

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That's an interesting design. Most membranes go on the front for the purpose of both extending response and minimizing high frequency absorption since most rooms require more bass control than high frequency absorption.

In a home theater, you'd want to leave the front corners as is but consider facing it somehow for rear corners for the reasons above.

Bryan
 

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It looks to me like there are some strange choices. The bits of timber facing the wall don't seem to serve a function. Why not just have a minimal frame?

The porous material on the back doubles up on cost, but if working in a resistive way it contributes almost nothing due to close proximity to the wall.

The filleted corners make it look wider than it is, but if you sent them back at a right angle to the front, you give up little but it would appear to have quite a lot less width. You could then make it wider at the front and have a bigger bass trap that looks about the same size. If you view it in 3D from the kind of angles you might see it in a room you will see what I mean.

As I understand membrane traps, they work best right near the boundary. Therefore, two sealed boxes in an L shape would work better. So you then have a triangle with the front part being a broadband resistive trap, then the connecting L shaped panel as seen from plan works as a pressure narrow band trap.
 
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