You'll feel more bass with a suspended floor above the concrete. Depending on the size of the room, and the speakers used, you could be fine either way.
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Mike, I've seen concrete work but I would float a floor if I had the chance. 2X6 or 2X8 with 12 or 16 inch centers would be great for flooring on a concrete slab. You didn't say what your equipment is so it makes it a little bit harder but I've heard analog gear with friends of mine and you don't want to have a lot of bounce in the floor which is why I would keep the centers closer together.
I took 2x4's and laid them on their sides, this will raise the floor 1.5 inches above the concrete (glue and nail them down). Then I put 1.5 inch thick foam panels between those for insulation. After that I laid down .75 inch tung and groove flooring on top of that..very solid floor that has the feel of no floor at all on top of the concrete (in other words, no give regardless of how hard someone might jump).
Thick carpet tops it off. Don't try to lay the tung and groove with out someone that knows how it needs to go down...it's like a giant puzzle and the last piece of the puzzle fits very tight.
In that case, put the carpet over the slab with some good padding. You don't need to add a wood floor and open your room up to potential vibrations. You also don't need the low frequency waves reflecting between the slab and the wood floor above it.
I like block walls instead of studs too.
Horns huh? I love horns. My home theater room speakers are all fully horn loaded.
Horns huh, have you talked to Jim Smith of Avantgarde? He will strongly beg that you put wood over the concrete. I talked to him in mid construction of my room and he talked me into the same basic construction as Dave described. I can't say if it's better since it's a tough one to A/B, but my horns sound pretty darn good in there. Call Jim, he's really helpful and would be able to really describe why it is so important.
Think of your floor as another wall. Concrete walls absorb nothing. A well constructed sub-floor will be just as good as cement in isolation from vibration.
While I don't agree with your choice of sound room construction...ie> all block room, sounds interesting with horns in a " you are there..LIVE sort of way.
I'm not saying that I disagree with your sub floor. If you built it the way you discribed, you did it right. It must be solid. I'm just not sure if it really has an advantage or not.
There is nothing special about my block walls, except they are built like your sub floor. Cinder blocks, 2x4's on sides, and foam panels in between, but covered with drywall. I can go outside the room with the all 10 speakers plus the subwoofer cranked up and place my hand on the outside of the walls and feel almost nothing. I have another room in my house that has stud built walls where I have a two channel horn system without a subwoofer. When I go outside the house and put my hands on the walls I can feel them flexing. I can also hear the music almost as well as I can when I'm in the room. I can't turn the volume up as much as I can in the theater room, because of room distoration. The walls and doors are moving the windows rattle, it's not good.
The theater room is 17' by 30' and has grown too small for all the speakers. I'm now drawing up a new room that will be 24' by 32'. I'm not saying the size is perfit for my system, but it should be better, and is all I have room for. Now you have me wondering if I should try your sub floor.
I would assume that wood over concrete wouldn't change all that much as opposed to carpeting that would absorb more of the sound. I just finished installing my own bamboo floors throughout my house and although I was working over a wood subfloor, in my search for flooring I saw that there were options for "glue down" wood floors. These are all the engineered type wood floors and actually go down quite easily. Dave is right regarding it being a bit like a puzzle installing it, but I found that it certainly wasn't rocket science and the only tools I needed were a tape measure, a $50 jigsaw, a rented pneumatic floor nailer, and a hammer and nails for the last boards that had to be "face nailed" I was able to lay about 250 sf a day including cuts for floor vents etc. Since you are going over concrete and would be gluing it down I think it would be even easier and faster for you.
Check out Ifloors.com very reasonably priced (I took a break from audiogon to research floors for a month or so with the same obsessiveness that we all do with our audio gear) They have a wealth of info on the site.
Personally...I like the look of wood floors with throw rugs...after pulling up my old carpeting, I have to say that it was so gross underneath that I will NEVER have wall to wall carpeting in any house I own.
I think I probably rambled on more than answering your question...sorry about that.
I should have been more clear. You have nothing to lose from the benefits that cement floors offer over most wood floors which are raised and set over a foundation or basement. Most have spring to them (not a good thing) along with other problems that result in poor vibration control.
A solid well constructed sub floor can offer many benefits over carpet/concrete only.
You can string wires.
It offers warmth to the room (I live in Michigan}.
It absorbs bass, concrete may be a good isolater but it is not a good absorber...pad and carpet absorb almost no bass.
Of course these are my opinions as A/B testing would be hard to do. Maybe Rives will see this thread and pipe-in on which method he would go with as he may have had a chance to do an A/B with before and after measurments.
I am also in the process of constructing a listening room, and am installing wood floor over slab. Out here in the Pacific Northwest, we like a moisture barrier over our slab, so this is what I am doing to install my floor.
1) Clean slab and paint with a sealant. In this case I am using a product by AFM-Safecoat, as it is non-toxic (non stinky) and the slab room is already enclosed as part of my house.
2) As an added moisture protection, I am laying 60 mil plastic sheeting, a single piece.
3) I purchased 2x6's and ripped them down to 2.25". They will be used as sleepers for the floating floor.
4) I purchased 2" thick foam for insulation, and will rip that down to 10.5" wide slabs to place between sleepers. This will give me a 12" spacing.
5) Floor goes down - 0.75" tongue'n groove, bringing the new floor up to 3" above slab.
The main reason I write all this is to advise about the moisture barrier. Plastic alone will likely do. But if you want more, be sure to use something that is friendly to your indoor environment - not something like asphalt foundation sealer (which really stinks!).