# Bass trap from gypsum drywall



## Guest (Jun 2, 2007)

Hi everyone,
I`m about to write my first post here, but first I would like to say thank you for the nice, interesting and useful enviromet you have created.

SO the question is:
Have anyone met somewhere on the net information about calculating the absorbtion coefficients of bass trap built similar to that described by Mr.Ethan Winer, but with gypsum drywall instead of polywood? Knauf drywalls are widely available in my country ( Bulgaria ) and I would like to use them for building basstrap. Of course there is allways the opportunity to build a small basstrap with known area and construction and then to measure the trap`s effective frequencies, but there is always the question how correct is the measurement setup. So I prefer to have a starting point. 

So any comments and sources of reading will be wellcomed.

Thank you in advance.


----------



## bpape (Sep 14, 2006)

If you use the standard formulas for such absorbers, you can simply substitute the mass of the drywall in the equation and it will tell you the frequency. Most likely, it will be MUCH denser than standard plywood used so the internal cavity will need to be shallower in order to get up into the upper bass/lower midrange.

Also, understand that this type of absorber no matter what the material is - is only good for about 2 octaves of coverage at most. You'll need to make 2-3 different tunings to cover what a broadband absorber would.

Bryan


----------



## Guest (Jun 4, 2007)

Thansk for the reply.
Since I plan to install drywall over the concrete and all the surface of the wall will be covered, it is not so hard to divide the wall an so to achieve wideband bass trap. I am only thinking about the depth of the trap and the type of fiberglass to be used. But this will become clear after some initial calculations.


----------



## bpape (Sep 14, 2006)

I guess I don't understand. How are you going to change the DEPTH if you're doing this by using the wall structure where the cavity depth is the same everywhere? The SIZE of the cavity doesn't matter - only the depth.

Also, remember that these MUST be sealed air tight and you want a minimal amount of denser absorbtion inside mounted close to, but not touching the front membrane. 

Bryan


----------

