Thanks for this great forum - till I started lurking here I thought I understood something about acoustics.

I am faced with the challenge of turning my 11 x 23 x 7.5 foot garage into a workable space for recording drums. This is a one shot deal, once this project ends I don't intend to use this space for recording.

On one short wall there is a garage door, on the opposite a tool bench made of wood, some metal shelves, metal drawers, peg board, the usual stuff. The wall behind the toolbench is concrete up to 3 feet and sheetrocked above that (split ranch house).

One of the long walls is sheetrocked floor to ceiling, on the other it is concrete up to 3 feet and then sheetrock. The half and half wall has 2 standard windows.

The room sounds awful, flutter echos abound, the ceiling is much too low, and I'm sure if I put something in there that produced low frequencies I'd find some standing waves too.

The room has only one advantage and that is I don't care what it looks like while recording. I can nail blankets to the walls, stack cardboard boxes, bags of old clothes etc...

So my plan was to do what I can with the walls using basic household stuff (free) and then build a set of gobos that I can create a temporary "iso" booth with, suspending one pannel from the ceiling. After the project I was going to move these into my normal music space for general use of all kinds.

I already have 96 sq feet of 2 inch wedge acoustic foam I got cheap ($.77/sqft). I figured since I was building a room inside a room I'll maximize the low end absorption since the foam would be spaced far away from the walls. The ratings on this foam are pretty much like you would expect. Good down to 500Hz. So so at 250Hz and useless below that.

I figured maybe I could mount it to some 1" 703 and/or some thin plywood or hardboard. But in order to create some isolation I would need to use a much denser backing. Perhaps some bifold closet doors (which would be self standing and would be angled to help prevent any parallel surfaces)?

If I back the foam on something dense will the dense substance essentially act like a wall and nullify whatever low frequency absorption I would get by having the foam away from the walls?

When using something dense for isolation does the dense substance absorb the sound or reflect the sound back into the space? In my case reflection back into the space is exactly what I'm trying to avoid.

If I simply mount the foam on thin plywood or hardboard will that act to any degree like a low frequency membrane absorber? I only need to get down to maybe 150 or 200Hz (22" kick drum).

Any suggestions? Isolation is nice, and I'm more worried about the ambient neighborhood sound getting in than drums getting out. But the sound inside the "iso" space is the most important factor.

Thanks in advance for any help you can provide!

PS. I was quoted a price of 35 bucks per 2x4 sheet for 2" 703 the other day. That's $350.00 for a 10 sheet box. Yikes!! Weird thing was the guy who tracked the stuff down for me was super helpful and also a recording musician. Needless to say I wasn't going to pay $4.30 per square foot for the stuff.

I am sure Ethan will give you good advice, but here is my 2 cents.
Have you thought about just cutting your drum tracks at a good studio then going back to your place and doing the rest?? For what you spend on doing a one shoot deal you could spend that in a real studio with a great room and great gear..
If you do build it, you may want to look into mineral wool, it is on .80 cents per squ foot.. That is for the 4"..

I thought very seriously about going to a studio, but the music is very complex with a lot of time signature and tempo changes. While he comes highly recommended I haven't worked with this drummer before so I don't know how quickly solid tracks will get put to tape.

Plus I already bought a pair of 414s to use as overheads.

A careful reread of the FAQ did answer one of my questions. If I understand correctly as the mass of the backing material increases the less effective the absorptive material will be. So I'm thinking at this point I'll cut to size 2x6 or 4x6 pannels of 703 (or whatever rigid fiber product I can get my hands on) wrap them in fabric and just glue the wedge foam to the front. Then frame only the outside edges to provide structural integrity so the pannels can be free standing.

"Then frame only the outside edges to provide structural integrity so the pannels can be free standing."

You may want to make frames on the back and mount stands to that. I think (I THINK MEANS I AM NOT FOR SURE) that mounting frames to the outsides will mess with the sound.. It is a matter of how good you want it.. One thing is if the drummer blows, all your work will not help.. You may want to go listen to him before you put that kind of work into a project like that. Ones again just my 2 cents.

Dave,

I agree with Myfie that by the time you construct a room within a room and also treat it properly, you'd pay less to go to a real studio. Even if the drummer takes forever to play his parts. That said...

> When using something dense for isolation does the dense substance absorb the sound or reflect the sound back into the space? In my case reflection back into the space is exactly what I'm trying to avoid. <

It sounds like you may be confusing isolation with absorption, and they're basically opposite goals. Materials and construction that isolate well reflect the very sound you're hoping to absorb.

> I wasn't going to pay $4.30 per square foot for the stuff <

Yikes, it should be 50 cents per square foot or even less.

--Ethan

Thanks for the input guys.

I think I'll just make free standing pannels that absorb and give up on creating any isolation - which I knew I couldn't get realistically in the first place since sound could always find ways around whatever pannels are constructed. This way no harm done if they don't make the garage a passable space - I can certainly use it in my primary music room where I have a whole other set of acoustic issues that some broad band absorption will help with.

Anyway thanks again.