Diaphragm / Membrane Bass Traps - Page 2 - Home Theater Forum and Systems - HomeTheaterShack.com

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post #11 of 18 Old 04-03-14, 08:28 AM
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Re: Diaphragm / Membrane Bass Traps

You're still talking 2 different things. If it's a non-sealed damped membrane, then the volume of the box doesn't matter, only the thickness and it should not have a back on it at all. If you ARE doing a sealed box with a back then it tunes narrowly.

No idea on 2lb high cut, sorry. 4lb MLV, not heard of it

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post #12 of 18 Old 04-03-14, 08:41 AM Thread Starter
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Re: Diaphragm / Membrane Bass Traps

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You're still talking 2 different things. If it's a non-sealed damped membrane, then the volume of the box doesn't matter, only the thickness and it should not have a back on it at all. If you ARE doing a sealed box with a back then it tunes narrowly.

No idea on 2lb high cut, sorry. 4lb MLV, not heard of it

My mistake, you mentioned sealed and unsealed earlier. I should have clarified: yes, I mean sealed. Here's an image to help explain the kind of box I'm talking about:




The brown is the wood, black is the membrane, and gray is some insulation. The rest is just air.
The membrane is pressed tightly to the wood, to make an air-tight seal. The box would have a top and bottom too, of course - thus, it's sealed.

Most of the box is shaped like a triangle, to fill up a corner of a room and (hopefully) increase the apparent depth.


The depth in the triangle area varies from 0" (left and right side of the triangle) to, let's say 8", at the center.
So, how would the depth be calculated in the triangle portion? Would it be 4"? (I need to put that into the calculator, to find the tuned frequency.)




If it's still not clear, I apologize.

Last edited by icor1031; 04-03-14 at 08:48 AM.
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post #13 of 18 Old 04-03-14, 08:51 AM
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Re: Diaphragm / Membrane Bass Traps

That's going to tune VERY narrowly. Figure the volume of that triangle plus the rectangular space and relate that to the volume of a rectangle the size of the face (gotta work backward).

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post #14 of 18 Old 04-03-14, 09:00 AM Thread Starter
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Re: Diaphragm / Membrane Bass Traps

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That's going to tune VERY narrowly. Figure the volume of that triangle plus the rectangular space and relate that to the volume of a rectangle the size of the face (gotta work backward).
The example above is 4" of insulation (though unstated and unscaled, lol). And unless I screwed up,
8" in that triangle should give 4" of volume if it were a rectangle the size of the face.


The blue one should mimic that.



The green one is an alternative design, with 200mm (8") insulation, with the triangle beginning 10" out from the corner. (5" worth of volume)



Does it look like I followed your directions correctly?
Thanks for your help!
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post #15 of 18 Old 04-03-14, 11:04 AM Thread Starter
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Re: Diaphragm / Membrane Bass Traps

I really like these two:

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post #16 of 18 Old 04-03-14, 02:59 PM
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Re: Diaphragm / Membrane Bass Traps

and those are limp membranes, not sealed ones which is why they are broader. Damped limp membranes will be even broader on the bottom side but still roll off on the top side.

In the end, what you do should be based on what the room requires. Do you know that part yet?

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post #17 of 18 Old 04-03-14, 03:58 PM Thread Starter
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Re: Diaphragm / Membrane Bass Traps

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and those are limp membranes, not sealed ones which is why they are broader. Damped limp membranes will be even broader on the bottom side but still roll off on the top side.

In the end, what you do should be based on what the room requires. Do you know that part yet?
Ah, . I don't want unsealed, because of the fibrosis possibility from the insulation. Unless putting 2mil plastic over the insulation won't ruin the affect in this kind of design?
I don't suppose you know of a calculator that shows the response like this does, for a sealed membrane resonator?


Also, no - I don't know what I need yet. I have a proper measurement mic. It's calibrated, not that it needed to be. However, I'm moving in about a month - and I'll be able to take measurements shortly.
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post #18 of 18 Old 04-03-14, 04:13 PM
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Re: Diaphragm / Membrane Bass Traps

Other than mine that I use to design our Scops Traps, nothing - but the formulas are available on the web.

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