Control Room Treatment Advice, please...

[el_goodo]

Hey all,

I have a control room finally completed and need to figure out the acoustic treatments needed. It will be primarily used for music mixing and some post production, sound design, etc. The walls are constructed as follows (inside to out): 5/8" sheetrock-3/8" mdf-1/4"neoprene-2 x 4 framing (fiberglass filled)-1/4"neoprene-3/8" plywood. Long story short - materials I was given. (Isolation is not the issue). Floor is wood parquet over joists. Ceiling is 5/8" sheet-rock laid over 2x6 joists 24" OC which are currently open on the inside.

My goal is to have a fairly flat response without being too dead. I know the room is small, but in particular I need the low end to be as accurate as possible. To that end, I'd like to devote the back wall to bass trapping/absorption. I'm thinking of a false wall/absorber that would traverse the slanted rear wall along a joist as seen in the pic. It would vary in depth from 1" to 19". It would be a nice bonus if I could incorporate some built-in storage, but it's not a deal breaker.

I was thinking of filling the space between the ceiling joists with 6" of fiberglass bat insulation and covering with fabric for a start (because it seems to be a lot of cheap, fairly flat, broadband absorption for the buck). I would consider installing it with paper out except over the mix position to keep the room from being too dead.

I would like to build corner traps of 2'x4'x4" Roxul RHT40 (Studiotips corner trap) that I could take with me when I move. The problem is, when I close up the ceiling joists with fabric, I would be hanging the traps against the false corner created with the joists, fabric and insulation instead of the true corner of the wall/ceiling. I'm considering making Super Chunks style traps but 20" long that would fit between the joists and be covered with the ceiling cloth tacked down the traps on the sides.

I would also treat side walls for monitor reflections as needed.

OK, let me summarize my questions:

1. I'd love an overall plan for treating ceiling, corner traps, and rear wall that would give give me as much bass trapping as possible while not making the room too dead (I've spent too much time in super-dead editing suites).

2. In the ceiling joists, would I be better off with 6" of fluffy insulation or 2" of RHT40 with a 3.5" air gap?

3. If I make 8 or 10 2'x4'x4" RHT40 modules for the corners, would they still be effective on the low freqs if they are not in the exact corners of the wall/ceiling? (they would be offset 5.5" by the 2x6 joists and insulation).

4. What would be the best construction of the rear wall for bass trapping and broadband absorption? Build the whole wall out of rht40? Hangers? Cavities?

I don't have a huge budget, but the RHT40 is cheap at .66/sq ft for the 4", .33 for the 2". I was thinking of ordering 20 or so of the 4" panels or a mix of 4" and 2" to get started. I have a lot of the other materials, so let's figure about $150.00 or so for insulation.

Thanks is advance for any help - and extra thanks to John for hosting such a helpful site!

Robert

[el_goodo]

Oops. Just noticed that 15' dimension at the top should extend all the way to the back wall...

Robert

[el_goodo]

Just a friendly bump as I would like to start work on the ceiling and rear wall treatment in the next few days.

In particular, I can't seem to find much data on the absorption effects of hangers. I've looked at several plans here for rear absorbers, but can't find any info on what sizes to make the hangers or how many to use and what sort of absorption I can expect at which frequencies. My goal is for the rear wall to be as absorbent as possible throughout the audible range while maximizing and broadening the bass trapping I will be achieving with the above mentioned corner traps and the existing drywall. My basic plan is for a wall of 4" Roxul RHT40 at the location in the drawing.

Thanks again,

Robert