I just though up an idea! I could hang 2' wide 4" deep traps off the ceiling around the perimeter of the control room in the front section with a 1" air gap on top. I would have all my gear under where these would be anyways so it's not like I would lose headspace there.
I would straddle 4" panels in the corners around the room. That would absorb A LOT more low end.
Then I could have the 2" stuff running down the middle all the way back on the ceiling.
That would work.
I'm thinking I wanna make the whole back wall a 12" thick broadband absorber and in the wall to wall corners build the biggest bass traps I can possible fit in them. Then put 2" traps at the early reflection points for the mix position and beside the couch.
Instead of frk can I use thick plastic like vapor barrier?
I have zero experience with that product so I can't help you there.
Should I use it on all the bass traps?
Yes anything in the corners
I'm also toying with the idea of stuffing the floor joists of the tracking room with about 6" of rockwool so the whole ceiling is a bass /broadband absorber covered with fabric. I already have a layer of 1/2" drywall attached to the subfloor between the joists. Would I get noticeable isolation doing this compared to what it would be like without anything in there and having the joists exposed?
I am not a iso guy, but if you put rockwool in the joists and cover that will fabric that will work well as a bass trap.
Would I would benefit from diffusion on the back wall of the control room or any parts of the tracking room?
Sure but you still would want 1 or 2 6" (or deeper) panels back there with the diffusion around it. As far as other places, it would work well anywhere behind the mix spot (ceiling, side walls, and back wall).