[Dracule1]

Hi, I'm building a dedicated 2 channel room in my house that is being built as we speak. It's about 15.4 W x 10 H x 22 L feet and located on the second floor - actually the only room on the second floor. I told the builder the front, back, and side walls have to be double sheet rocked (total 1 inch in thickness). The walls have R15 insulation, the floor has R30 insulation, and ceiling has R40? (blown insulation). Floor will be carpeted. Now the problem is this. On the other side of one of the long side walls is the attic space. I thought that the outer side of the long wall facing the attic space will have a single layer of sheet rock (half inch). But the builder just told me there will be no sheet rock, just the insulation and a thin "waterproof" insulation. Same situation for the front wall possibly. Will this be a problem acoustically?
The back wall has single sheet rock on outer side and the other long side wall is actually is part of the wall of the house facing outdoors lined by brick.

[MaxCast]

I don't think it will be a problem.  1/2" seems kind of thin.  Can he double it all around?  I don't think you want rock-stud-rock as this creates a chamber which will resonate.  Doubling the rock will lower the resonate point. 

[TRADERXFAN]

You may wish to consider http://www.gedlee.com/Home_theatre.htm  book. It shows techniques such as CLD drywall which you could take advantage of while you still are building. This can be very effective for bass damping...

There are some free chapters posted on his site, that should help you see where he is coming from.
Chapter 4 page 68- the quick summary.

He posted on the subject here, in audiocircle:
http://www.audiocircle.com/index.php?topic=56687.msg511881#msg511881

[Dracule1]

Hi MaxCast,  the room will be double sheet rocked (1 inch total thickness) for the front, back, and side walls - for the inner walls facing the room.  What I'm worried about is the outer walls of the front wall and one long side wall where it will be open to the attic without sheet rock.  You are saying rock-stud-rock is a bad idea because of resonance - but most rooms have this arrangement.  So you think I should leave the two walls as is without the sheet rock on the outer wall?

[bpape]

Having no rock on the outer side by the attic will drop the resonant frequency of that cavity rather than just having 3.5".  It's just fine and actually preferable.  If you do 2 walls together, you only want drywall on the 2 outer surfaces, not on the ones facing each other.

Bryan

[Dracule1]

Hi Traderxfan, thanks for the book reference.  Don't have time to read it now, but what does CLD stand for?  Is it different than standard gypsum sheet rock?  The dry wall is being put up in my room as we speak, so I think it might be too late to use CLD drywall at this point.

[bpape]

CLD is Constrained Layer Damping.  You can use Green Glue between the 2 layers to get this effect and excellent performance.  There are drywall products that have the damping built in.  From what I've seen, to get close to the same performance as the Green Glue, you have to get their most expensive drywall product.  it takes about 3 guys to move it around.  Can't even imagine doing a ceiling.  The Green Glue and double drywall will perform better and it's a cheaper solution - just takes more time. 

Bryan

[Dracule1]

Thanks Bryan.  Where can I get this green glue?

[bpape]

PM Sent

[Dracule1]

PM sent

[bummrush]

Damn well make sure its not from China!

[Dracule1]

I like the smell of sulphur in the morning!