I'm making a HT in my basement where sound insulation is paramount. Therefore, I'm doing a (more or less) true room-in-room (the inner room only has mechanical contact with the floor (which in turn is mechanically insulated from the walls)), with triple layers of sheet rock (GG'ed between each layer), double sound insulated doors etc. etc.

Now, I'm wondering if all this is a waste of time if I install in-wall surround/back speakers? Before you scream "YEEEEES!!!", please look at the sketch below (seen from above):

http://www.avsforum.com/avs-vb/attachment.php?attachmentid=103720&stc=1&d=1204552165

As shown above, I'm considering making "back boxes" for each speaker with the same thickness as the walls - that is triple layer of sheet rock.

Would this keep the "integrity" of the wall? The box would of course be closer to the concrete wall than the rest of the wall (close = bad when it comes to sound insulation), but how much "damage" would this limited area do?

Just ran across your thread. I am buy no means a sound expert but I would think your design would work quite well. Some of the in-wall speaker manufacturers use a thin metal or plastic enclosure on the back side of their speakers and claim no sound escape from the enclosure on the back side. It would appear that your design has much more sound integrity than what little the manufacturers give you. I'd run with it.

Good luck.

I plan to do something similar in my theater. However, I would talk to the manufacturer of your speaker to see how that would affect the sound. Some inwall speakers are made for an infinite baffle behind them and may or may not have a preferred volume for the back box. Others, like mine (Triad), are built with a box already in place, so an additional enclosure won't affect them.

CJ