Platform as a Bass Trap?

[Griffster]

I am getting ready to build a platform for a second row of seats and was wondering if it is possible to use the riser as a bass trap?

I was thinking of cutting holes in the front and back and stuffing between the studs (2X10) with fiberglass insulation.

It seems somewhere I've read about someone doing this, but now I can't find it, and a search was no help.

I'm interested to hear what everyone thinks.

Thanx!!


Griff

[ThomasW]

Have you 'mapped' the in-room bass response to see this is needed?

Cutting smallish holes won't do much of anything. Cutting out entire sections of floor and covering them with expanded metal lath would create a trap.

[Griffster]

Alright,

I'll profess my ignorance and admit I have no idea how to "map" the in-room bass response. As for smallish holes, I was thinking 6-8" holes at the ends of each bay of the platform.

Guess maybe this wasn't such a good idea. I was hoping it might help with taming the liveness of the room until I could figure out what i need for acoustic treatments.

[Dennis H]

I was thinking 6-8" holes at the ends of each bay of the platform

That's not going to do much. Think about it, even if all the sound hitting your holes gets absorbed, you've got sound hitting and reflecting off 100s of square feet of walls/ceiling/floor and a couple of 6-8" absorbers which are tiny in comparison. Absorbers need to be big, like many square feet, if they're going to do much at bass frequencies.

[ThomasW]

Mapping the room involves measuring the bass response of the room using a grid. That tells where bass traps are needed.

6"-8" holes will do nothing. A standard fiberglass bass trap is 24" thick, flexible membrane traps are thinner....

http://home.comcast.net/~thomasw-2/SubwooferSetupandEQpage9.html

[PMazz]

Didn't John Kotches do a Dennis Erskine designed platform that sounds familiar. The little info I had made it seem to be a Helmholtz resonator in design. I couldn't imagine it working any other way.

Pete

[ThomasW]

One could certainly make the platform into a Helmholtz resonator. It would be necessary to determine what tuning frequency is needed.