John Sayers' Recording Studio Design Forum Archive

hello all.
I sure have enjoyed learning on this site and hope to repay someone else down the road with informed acoustic advice.

a little background: I just moved into a house with a separate guest house that is becoming my new studio. I don't work with bands often but I do drum kits from time to time, never really late into the night. My control room is isolated just fine for my purposes and reasonably so from the tracking room.

The T-room is 10' wide, 18' long with 9' ceilings. Construction is regular 2x4 framing. 1/2" drywall inside, residential batted insulation in the cavity and only 3/8"(or even thinner) rough paneling with vertical wood strips outside. Only two of the walls are facing outside, the other two have the control room & bathroom between them and the outside world. Two big issues are a wall mounted heater/ A/C unit and two 4'x6" double pane(1979-ish) aluminum windows. There is also a door to the outside world, solid and weatherstripped all around. Ceilings are 5/8" drywall, 2x6"s, blown-in insulation, attic space, sheathing and cement tiled roof. Seems very quiet and solid up there.

Yesterday I tried a drum session in the tracking room. One song in the middle of the day to asses the leakage problems..and to a lessor extent the inside acoustics. I stuffed sleeping bags in to the windows as best as possible and a few over the A/C unit. In walking around the outside while the drummer was tracking the walls were surprisingly isolated but the windows were not. The A/C unit was just about like an open window into the room...as I expected.

My plans are to: seal off one of the windows and get something like a Milgard sound control for the other. Remote mount the A/C unit to a large storage closet on the back of the guest house. Add material to the outside wall. Maybe add a layer of drywall to the inside two walls.

Questions:
1. I have a bunch of 1/2" glued chip type plywood(OSB maybe?) and 1/2" siding. I have pulled off the outside cosmetic strips and was planning on screwing on this stuff with lots of caulking and seam sealing. Good idea?
2.Tips for remote mounting A/C unit. I was planning on making a return and duct work and have a master switch in the tracking room?? would be about a 15' run with ductwork
3.should I just screw in the extra layer of drywall or float it somehow R/C. 4. If not do I screw it through the first layer into the studs or just to the other drywall somehow?
5. I was planning on sealing one window by framing it outside with 2x2s around, stuffing with insulation and adding plywood like the existing outside wall. then, I would drywall up the inside stuffing more insulation against the glass?? this leaves me with an inside windown frame, perfect for a bass trap of somekind...
6. would greenboard-gyp add mass and isolation to the outside wall?
thanks so kindly!!

Questions:

1. I have a bunch of 1/2" glued chip type plywood(OSB maybe?) and 1/2" siding. I have pulled off the outside cosmetic strips and was planning on screwing on this stuff with lots of caulking and seam sealing. Good idea?

Only if you can completely fill any voids between the existing and new siding - you don't want ANY air gap between layers of a single mass leaf, or it will be weakened acoustically; mostly at lower frequencies.

2.Tips for remote mounting A/C unit. I was planning on making a return and duct work and have a master switch in the tracking room?? would be about a 15' run with ductwork

That would depend on what kind of AC unit - generally, you want larger than normal diameter ducts, fairly long, with 2-3 bends per run, and no shared runs between rooms.


3.should I just screw in the extra layer of drywall or float it somehow R/C.

Not sure what extra layer of drywall you're referring to, you need to clarify this one more -


4. If not do I screw it through the first layer into the studs or just to the other drywall somehow?

If you're referring to a second layer of drywall on studs, first mark (on masking tape along the intersecting walls) the EXACT location of each and every screw, then apply the second layer at right angles to the first layer, and MISS the existing screw locations - screws through existing drywall and into studs, full schedule.

If starting a NEW wall, only the FINAL layer would get full schedule fasteners. Wall insulation will help minimise the flanking caused by penetrating screws through both layers, but if it's a single stud wall frame you would need to use RC on one side to keep this flanking to a minimum.


5. I was planning on sealing one window by framing it outside with 2x2s around, stuffing with insulation and adding plywood like the existing outside wall. then, I would drywall up the inside stuffing more insulation against the glass?? this leaves me with an inside windown frame, perfect for a bass trap of somekind...

Be careful here; you can very easily end up with a triple or quad leaf barrier doing this. Can you post a drawing showing layer by layer (including air) from outside to inside?

6. would greenboard-gyp add mass and isolation to the outside wall?

While greenboard is better at high moisture locations, it is still gypsum; as such, it has very low resistance to "racking", and should not be used on outside wall frames. Building up mass at that location would be better done with extra layers of OSB or waferwood, tightly nailed, properly flashed (where applicable)

While re-reading this, it occured to me that you might (6) have been referring to gypsum INSERTS between studs; if so, I'd go with greenboard and make sure the wall is dry inside with a proper air barrier toward the outside.

Hope this helps... Steve

Thanks so kindly.
I was referring to adding another layer of mass(drywall) to the inside finished wall since it's only 1/2" and has few interruptions so hanging would be easy....so screw into the stud through existing drywall, missing any screws. No glue. Correct?

I tried a test panel to the outside wall. caulked heavily and screwed together. It seems as if it sucks up to the siding quite well leaving no air space...if any they would be 1/32" or so. I think I'll continue.

would adding a sealed panel 2 & 1/2" away, stuffed with insulation, from a double pane window be triple leaf? ...seems to be only 1/4" air space and decorative window grids in between the glass. Doesnt seem to be enough airspring to make a leaf...correct me please. Was thinking about gluing some Homasote(soundboard) to the glass(one side) to dampen. Then the window box would be filled with 703 inside the room for a bass trap.

thanks for the a/C info. how does one go about fitting ductwork to the front of a window-type A/C unit??
again, thanks....

Correct on addition of the drywall, including no glue -

Yes, still triple leaf - even a 1/4" air gap can cause resonance in the 250-300 hZ range, depending on glass thickness, etc - if you can't get additional mass items to fit flush with the glass, you shouldn't use them at all. Better to place MORE mass in the secondary leaf. If you already have "thermopane" type glass, as in double glass with nitrogen-filled center, that is already double leaf. Placing more mass anywhere but tightly against either of the sides of that type glass will create a triple leaf.

Triple leaf isn't bad throughout the audio spectrum, just mainly at low mid to low frequencies; but those are always the hardest to stop, so they should be considered foremost.

Window AC units - have you seen this -

http://www.johnlsayers.com/phpBB2/viewtopic.php?t=644

How to fit ducts to a window unit? some you can't, others maybe. That's why I asked Rod Gervais about this (link) idea, and he saw no reason it wouldn't work. Basically the same as leaving your bedroom door open during the summer, and allowing the BR AC unit to cool the rest of the house some by putting a fan in the doorway to the BR, on the floor pointed out toward the rest of the house... Steve

Interesting how common sense/gut feelings about how well something should work are not always so...
OK, so the triple leaf deal is out. Maybe I'll just take out the glass and build a double leaf wall, adding mass to the outsides.
Any thoughts on the effects of squishing regular R13 insulation bats down to a 1 & 3/4" thickness? I have already sealed off one such window in my control room a couple weeks ago by screwing 2x2s to the outside wood frame, stapling bats in and screwing on 5/8" plywood. Upon playing my monitors as loud as I'll ever want and going outside, any leakage disappeared. Now I realize this is triple leaf as well but I won't be doing any drums in there. ..I could always undo the 30 or so screws and redo...

I've done a search on glass blocks..not much is known. If I seal off the window in the tracking room, outside only(first leaf). would a small glass block wall in front (on the inside of the room) constitue a triple leaf? ..or is the block considered one mass?
thanks again.
where on the west coast by the way mr knightfly?

Squishing fiberglass down inside a barrier won't cause any problems until you squish it to the point that it causes coupling between the leaves of the barrier; in fact, it's better to squish than to not squish in most cases, because this helps damp the panels so even at their resonant frequencies they don't ring.

Glass blocks - not much info out there, you've probably already found this -

http://www.glassbrickcompany.com.au/pag ... nical.html

Near as I can tell, glass brick would work same as hollow concrete brick - with an air gap between the surfaces, they would act as a double leaf barrier on non-RC solid, single studs -

I'm about 90 miles south of Portland, OR - about 7 miles to the nearest 1-horse town, about 15 miles off I-5... Steve

Thanks again. hello Oregon.

So far I'm doing OK then. I think I may try the glass blocks as a floating windown not sealed up, with 703 around and a lighted wall behing them for some vibe in the room. The sill inside is fairly deep. This would eliminate the possible triple leaf.

It is so cold down here this week. Normally in Ca cold A/C is the only concern in a studio since the gear is enough to heat up a room. I suspect that I have some insulation problems, and consequently some sound leakage problems along with..The heat/A/C unit is almost like a window outside, the window is poor quality and the Recessed 'pot' down lights are my first suspects. Up in the attic the insulation(blown-in celulose) is held back from the lights with cardboard rings. Ideas? Is there fire/ heat type insulation.

Ideas on mounting another sheet of drywall on the ceiling..on top of the cottage cheese acoustic crap?? would that be almost a way of getting some miniscule air spaces and somewhat floating of the new sheet?? ..just an idea. I've scraped that stuff before and it's way fun!!(sarcasm) Thought maybe then I could surface mount the lighting with no holes into the attic for sound escape.


I've read many time about cutting the drywall inbetween the studs in order to gain access to the first outside leaf. Commonly it says to use the cut pieces to add mass to the first leaf by screwing them on.
The interior wall between the tracking room and to the bathroom and another to the storage are 2x4 stud walls with 1/2" on both sides. The one to the storage room is open studs inside the storage room. How do I mount/screw drywall to drywall? It would seem the screws would spin before a solid fastening...
Is this a place for glue?
appreciatively,
kel

motown59 wrote: Ideas on mounting another sheet of drywall on the ceiling..on top of the cottage cheese acoustic crap?? would that be almost a way of getting some miniscule air spaces and somewhat floating of the new sheet?? ..just an idea. I've scraped that stuff before and it's way fun!!(sarcasm) Thought maybe then I could surface mount the lighting with no holes into the attic for sound escape.

Hi kel, I don't know how much of a mess you are willing to make removing the 'cottage cheese,' but IME it came off fairly quickly with some water. We got one of those pesticide type sprayers to spray the water onto the ceiling. After that, we made quick work of it with a few large putty knives.

BTW, I am in so cal also.

Hey GD, nice to meet you..
yea, I've done the sprayer/water/scrape thing before. I might do it again, especially if I rip up the carpet.

catch ya soon