Membrane Over Bass Traps - What Do You Suggest?

[Mark Fuller]

Hello,

I plan to make up to 6 large rectangular boxes filled with unfaced pink fluffy.
They'll will be 48" long, 15" deep and roughly 32" high (still deciding on exact height) placed on the floor against walls with Guilford speaker grill wrap.

Which material would you suggest to be used as a membrane on the outer facing surfaces?
Paper like grocery bag material? Thin plastic sheets like you'd use to cover a broken window? Heavy duty Hefty yard bags? Something else?

Which pink fluffy will have the most impact on lower frequencies in combination with a membranous outer-facing surface?

A bit more low-mid control, less low reverb times, maybe I can attenuate slightly my standing wave issues from 80 hz on up, are my goals. I'm fairly happy with the space using numerous 4" 705 FRK clouds and panels mixed with 4" 703.
I intend to replace 703 diagonal corner panels with Superchunks perhaps with the same materials as the rectangles as well.

Any advice would be appreciated.
Btw, I cannot attach these to the walls in any permanent fashion.

Thank you!

Mark

[JasonFoi]

What is your intent in adding the membrane? Are you trying to turn them into pressure traps or just cover them. If youre making pressure traps, what Fc are you targeting? Are you sure your intended location is a high pressure area for your target frequency? On the fluffy fiber, at that depth you should use cheap light unfaced insulation batts with a GFR around 5000 if just a velocity trap, or pretty much whatever is cheaper for damping a pressure trap.

[Soundman2020]

Which material would you suggest to be used as a membrane on the outer facing surfaces?

As Jason already said: Why do you want to put a membrane on them?

Are you trying to create a limp-membrane trap? If so, what frequency do you want to tune it to, and why did you select that frequency?

Which pink fluffy will have the most impact on lower frequencies in combination with a membranous outer-facing surface?

If you are building a membrane trap, then that would depend on the frequency you tune it to. But assuming you are targeting modal issues, you should use lighter insulation. If fiberglass, probably around 20 kg/m3 or a bit less. If mineral wool, then maybe around 40 kg/m3.

A bit more low-mid control, less low reverb times, maybe I can attenuate slightly my standing wave issues from 80 hz on up,

Those are three entirely different and unrelated goals. A membrane trap would only help with the third one. And you must have a very, very small room if your modes start above 80 Hz... Dimensions?

I guess I'm just repeating what Jason said, in reality... with a couple of extra details, maybe....


- Stuart -