Floor Joists into Bass traps?

[RodC]

Im in a basement with exposed floor joists. If I attach 4" of Roock Wool or OC 703 between bottom edges of the joists (flush with the bottom edge), Then cover with some fabric would this make an effective bass trap?

This would save me the 4" hanging down if I mount them up in the joists.

There would be about 6" air gap between the insulation and the upper floor.

I plan on treating the corners also but this seemed like an easy thing to do.

[carlsaff]

Yes. This is exactly what I did in my basement room. You'll want to use fabric that keeps fiberglass shed out of the room or put another layer between the fabric and the fiberglass. I used thin black polybat (used for sewing) as a protective layer above my final "finish" fabric.

Making it look nice is tricky. I really lucked out with mine. It looks fantastic. Virtually no seams.

[RodC]

I wonder if I could set it back in an inch or 2 and cap it off with 1/8" plywood.

If you look at Ethan Winers Deep bass design it is capped with Plywood:

http://www.ethanwiner.com/BTPlans.gif

Hopefully Ethan will stop by and let me know if this would be effective.

[carlsaff]

Hm... if you did, I wouldn't expect it to work at the lowest (modal) frequencies. But I could be wrong.

[RodC]

Hm... if you did, I wouldn't expect it to work at the lowest (modal) frequencies. But I could be wrong.

Thats what I thought at first, but if you read his article the ones with 1/4" works down lower. I guess it has to bounce around in there and go through the insulation more if its covered with wood.

[Kyle]

I wounder if you could cap some joists with 1/8 inch plywood, 1/4 inch plywood, and cloth only. I've had this same question as I too record in the basement. It seems like you could also set the traps at different depths inside of the joist ramdomly across the basement. this would vary the air between the floor boards and the 703 or doubled layer of 703. The joists themselves might act as diffusors.

The plywood may cause the high freq. to bounce around the room and cause some comb filtering. I can hear the difference between my basement (open rafters) and my friends basement with a finished ceiling. Esp. on the cymbals.

It might be cool to have a dead end of the basement and a live end, inters of broadband absorbtion and low freq absorbsion.

I think its a very cool idea. I'd love to see some photos if you do it.

[RodC]

I wounder if you could cap some joists with 1/8 inch plywood, 1/4 inch plywood, and cloth only. I've had this same question as I too record in the basement. It seems like you could also set the traps at different depths inside of the joist ramdomly across the basement. this would vary the air between the floor boards and the 703 or doubled layer of 703. The joists themselves might act as diffusors.

The plywood may cause the high freq. to bounce around the room and cause some comb filtering. I can hear the difference between my basement (open rafters) and my friends basement with a finished ceiling. Esp. on the cymbals.

It might be cool to have a dead end of the basement and a live end, inters of broadband absorbtion and low freq absorbsion.

I think its a very cool idea. I'd love to see some photos if you do it.

Thats exactly where I was going.

[Ethan Winer]

Rod,

> Im in a basement with exposed floor joists. <

You can use 4-inch rigid material at the bottom of the joist cavities, or just stuff the whole thing with 12 inch thick fluffy fiberglass. I wouldn't try to turn that into plywood panel bass traps for a variety of reasons:

1) You'd need to make all the cavities air tight which is a pain. 2) And that only treats the floor-ceiling direction. 3) And a ceiling should be a absorbent at mid and high frequencies too. So for all those reasons...

> Then cover with some fabric <

Exactly.

--Ethan

[RodC]

Rod,

> Im in a basement with exposed floor joists. <

You can use 4-inch rigid material at the bottom of the joist cavities, or just stuff the whole thing with 12 inch thick fluffy fiberglass. I wouldn't try to turn that into plywood panel bass traps for a variety of reasons:

1) You'd need to make all the cavities air tight which is a pain. 2) And that only treats the floor-ceiling direction. 3) And a ceiling should be a absorbent at mid and high frequencies too. So for all those reasons...

> Then cover with some fabric <

Exactly.

--Ethan

Thanks for the reply Ethan, would 12" thick fluffy fiberglass be as effective as 4" of Rockwool?

I guess I would use 12" without the paper facing and seal with fabric.

What if I only did 1 out of every 3 joists, would it be worth the effort? I would hate to seal them all off, its sorta part of the style of the room.

[Ethan Winer]

Rod,

> would 12" thick fluffy fiberglass be as effective as 4" of Rockwool? <

Probably similar. I never compared those directly so I can't say for sure.

> I guess I would use 12" without the paper facing and seal with fabric. <

Exactly.

> What if I only did 1 out of every 3 joists, would it be worth the effort? <

If you don't want to do the entire ceiling, at least treat the first reflection points, and all around the perimeter to cover the important wall-ceiling corners. And above anywhere you plan to use overhead microphones.

--Ethan

[Etnier]

Before you get started, consider screwing layers of 1/2" & 3/8" sheetrock directly to bottoms of the floorboards: staggered seams and caulked. THAT will have a nice effect on noise transmission in both directions.

[RodC]

Before you get started, consider putting layers of 1/2" & 3/8" sheetrock directly under the floorboards: staggered seams and caulked. THAT will have a nice effect on noise transmission in both directions.

\

That would prob help noise transmission but Im not really conserned about that. Just want to tame down the bass.