Standing wave issues in a home theater

[bpape]

On the back side, if it's not finished, that's an opportunity to pull the drywall and add insulation (not foam). That will help deaden things a bit and also allow at least that one wall to function partially as a bass absorber.

Bryan

 

[highfigh]

On the back side, if it's not finished, that's an opportunity to pull the drywall and add insulation (not foam). That will help deaden things a bit and also allow at least that one wall to function partially as a bass absorber.

Bryan

Right- and it also makes it possible for me to do this without disturbing the finished side, which has been the sticking point for The War Department at the house. She's tired of the whole process (starting with the fire they had on the first floor) and I'm happy because it simplifies the treatment.

I plan to run a few tests and will watch the response changes as I and someone else lean into the wall to keep it from resonating. If necessary, I can add splines to the studs to stiffen the wall- I think I'll find that it's radiating in the range with the hump. Then, it'll be a case of using traps and panels because the room will be much more uniform.

 

[bpape]

If you want it to act as a bass absorber, you'll want to insulate it, drywall the back side and NOT stiffen the wall. Larger cavities have lower resonant points and will absorb lower.

Bryan

 

[highfigh]

If you want it to act as a bass absorber, you'll want to insulate it, drywall the back side and NOT stiffen the wall. Larger cavities have lower resonant points and will absorb lower.

Bryan

I know, but it's not that the cavity is larger, they used steel studs and they're more flexible than wood. Where the left wall has 2x6 metal studs/3/4" Celotex/5/8" drywall/foam on the theater wall backside and 5/8" drywall on the finish side of the adjacent room , the right wall is 2x4 metal studs/3/4" Celotex/5/8" drywall with no foam and unknown insulation, at this point. The backside is drywalled, but not mudded and taped (this will definitely change).

In your opinion, wouldn't I want the room to be consistently rigid and dead all the way around, instead of having one wall in business for itself? It would seem like more of a blank slate for analysis and treatment, to me. I have to think symmetry would be desired in a space like this.

 

[bpape]

Actually, I would not necessarily recommend all walls act the same. I've intentionally done some room designs where 2 walls are studs 16OC and 2 walls are 24OC. This is specifically to broaden the range at which the walls absorb - and - minimize one peak frequency which is most transmitted to other parts of the house.

The way I look at the current room is that 3 walls have already been ruined as bass absorbers. You have one left to make work FOR you instead of against you. I'd use it that way.

Bryan

 

[highfigh]

Actually, I would not necessarily recommend all walls act the same. I've intentionally done some room designs where 2 walls are studs 16OC and 2 walls are 24OC. This is specifically to broaden the range at which the walls absorb - and - minimize one peak frequency which is most transmitted to other parts of the house.

The way I look at the current room is that 3 walls have already been ruined as bass absorbers. You have one left to make work FOR you instead of against you. I'd use it that way.

Bryan

OK, so I should attach some cleats to the studs so the rigid fiberglass can't touch the drywall on the room side and let it act as a membrane absorber, right? Is there any point in doubling the drywall on the backside?

Thanks again.

 

[bpape]

You can double the drywall on the back side for isolation if you need to. Don't worry about the insulation touching. It will act as a damped mambrane and work down fairly low.

Bryan

 

[highfigh]

You can double the drywall on the back side for isolation if you need to. Don't worry about the insulation touching. It will act as a damped mambrane and work down fairly low.

Bryan

Can you define "fairly low"? The problem region is from 60Hz- 110Hz, where I have a big hump.

 

[bpape]

Depends on the framing but usually centered around 90ish and good for almost an octave on either side to a reasonable effect.

Bryan

 

[highfigh]

Depends on the framing but usually centered around 90ish and good for almost an octave on either side to a reasonable effect.

Bryan

That'll work, for me.

 

[Shock]

Tell those bastards to sit down you're trying to watch a movie!

 

[highfigh]

Tell those bastards to sit down you're trying to watch a movie!

They never listen.

 

[Warpdrv]

Where did you get the OC 703 highfigh...

Local place... ?

krzywica and I are probably gunna do some DIY panels for him..

 

[highfigh]

Where did you get the OC 703 highfigh...

Local place... ?

krzywica and I are probably gunna do some DIY panels for him..

Acoustech, behind Culver's on Hwy 100, South of Greenfield Ave. They stock 1" but would need to order 2" and they can order Roxul, too.

 

[Warpdrv]

Cool..... thanks so much...

For some reason I had a hard time trying to find a place to get it locally...

 

[krzywica]

Sweet!!..I can't wait to start this project....hopefully I will be able to do some documentation this time....once the booze starts flowing that can prove difficult though.

 

[highfigh]

Cool..... thanks so much...

For some reason I had a hard time trying to find a place to get it locally...

C.A.S.H. is another place that carries it but their price is higher. I went to Acoustech when I set up the theater room at the Flanner's store when they were still in Mayfair Mall. The room was small and had really bad flutter. The bass was decent enough but the 1" worked for the problems the room had. Once I did that, the salesmen asked if I could do something in the big demo room where the Mac, Klipsch and other upper line stuff lived. That one was less acoustical and more blocking the sound from the HVAC unit that was above the suspended ceiling, rumbling so bad it was impossible to really hear the sound quality. How they did as well as they did with that making all that noise from '62 until I quieted it is beyond me.

 

[popotoys]

Could you not consider an Anti-Mode 8033B and it's on sale for 163€

http://www.dspeaker.com/en/home.shtml

 

[highfigh]

Could you not consider an Anti-Mode 8033B and it's on sale for 163€

http://www.dspeaker.com/en/home.shtml

I could probably consider it but it's not my project- I'm helping a friend do it for someone. Also, I wouldn't buy anything because I hope it works. It looks interesting, though. The client is having his guys pull the drywall on the backside either today or tomorrow (I hope) and they'll insulate then. Once the drywall goes back on, we're instructing them to mud and tape the joints and put a second layer of drywall on, mudded and taped. Only then, will I see if it works. They didn't follow my/our instructions, so if they only want me to go to a certain point, I'll get it as good as I can. I wanted non-parallel walls, too, but didn't get them.

I suspect they'll be happy as long as I tell them that it's as good as it can be without demolition to fix things and without adding 4"-6" panels on the finished side of the walls. I don't like being in this position but....