Coming right along. Make sure you caulk the bottom plate to the concrete before you put your mat down so you don't lose isolation there.
Also, if you haven't planned the door position yet, try to keep it out of the corners and offset at least a couple feet if not more from the center of the rear wall. That leaves more options when it comes time to treat the room.
Bryan
Done and done. We laid a polystyrene-dimpled membrane first, (DeltaFL.com) then the plywood first to make a subfloor. So, the entire basement is on one big floating floor. It was glued together at every seam with industrial adhesive. All of the walls are then glued and screwed to the subfloor, with an extra bead of glue along the inside edges of the sound room.
The back door is about 3' into the room along the back wall, which is about 15' wide. I'll post a pic of the layout in my gallery soon.
There has to be some weird soffits along the back because of a return duct from upstairs that can't be moved. I'm debating on whether to make the bump out symetrical now... probably will.
That looks to be a beautiful audio room, seeing with my mind's eye. In the end, you will have pride of not only assembling the tinkly bits but also the structure in which they reside. What an opportunity.
It's a dream come true, I'll be honest. I figured this will be 'my big thing'... I'll have a great place to hear music at its best and watch movies in my own theater.... and that's just amazing to me. You only live once.
-C