I've never posted in this forum before, but I've definitely gleaned a lot of useful information here. So thanks very much.

My question is regarding soundproofing - specifically what I need to do on the floor of a room within a room HT in a basement. Is it necessary to isolate my HT room floor from the concrete floor using something like the following layered system: 1/2" rubber mat, 3/4" plywood, 2x4 frame filled with Roxul Safe and Sound, 3/4" plywood, and then carpeting? Or can I just let my HT room sit directly on the concrete floor? How much mechanical vibration will really be transmitted through the concrete to the adjacent rooms if my framing and carpeting sit directly on the concrete floor?

Since my drywalled ceiling will be dropped from the main floor joists, I'm low on head space as it is, so I'd like to limit my floor height as much as possible.

Thanks.

Your concrete slab is an excellent transmitter of sound.

So Dennis, do you think that my current layered floor system will be fine, or is there a better and less space consuming way to do it?

Thanks.

Am I misreading, or are you talking about your basement concrete floor?

Hi scaesare. Yes, I am talking about a concrete basement floor. When I was referring to my layered floor system, I was describing what I plan to place above my concrete to achieve an isolated room in a room. Currently my plan is to have a 1/2" rubber mat sitting on the concrete, then 2x4 frame construction filled with isulation, then a 3/4" piece of plywood, then carpet. I am also entertaining the idea of using just 1/2" rubber mats and (2) 3/4" pieces of plywood as my floor. Then I'd simply attach my walls to the plywood floor - I'd still achieve isolation and would save some height in my room.

What are your thoughts?

If you do it right, the 2nd option will work fine.

Bryan

Hi scaesare. Yes, I am talking about a concrete basement floor. When I was referring to my layered floor system, I was describing what I plan to place above my concrete to achieve an isolated room in a room. Currently my plan is to have a 1/2" rubber mat sitting on the concrete, then 2x4 frame construction filled with isulation, then a 3/4" piece of plywood, then carpet. I am also entertaining the idea of using just 1/2" rubber mats and (2) 3/4" pieces of plywood as my floor. Then I'd simply attach my walls to the plywood floor - I'd still achieve isolation and would save some height in my room.

What are your thoughts?

OK, my theater is also in my basement with slab floor. I asked for the clarification because Dennis' reply seemed to indicate that the slab would be transmitting sound to some other living space.

Given that your slab is sitting on earth (and not a living space below), then there should bo no reason to build up a framed floor on top of it. The only coupling source to the rest of your structure would be that your basement side walls (likely also 6-8" thick concrete) are sitting on that slab. However those walls are also largely buried, which also dampens the sound signficicantly.

I simply used a good heavy pad and nice thinck carpet directly on top of the slab.. and this primarily to treat the in-room acoustics. I decoupled my walls and ceiling where they are common to the rest of the structure, and attached framing directly to my slab. No problems with sound tranmsission via the concrete whatsover.