Bass trap question, Rose Lane Studio, Carpinteria, CA

Hi there, After some 12 years I'm realizing what a fantastic resource this forum has always been. Glad to be back, glad to be building again. As I'm in my 60's now, this is likely my last studio! There is some more info under "other studios" John helped me a lot with my old studio in Montecito, CA., there are some pictures under "sjoko's studio" in the "completed" section. This project is a re-build of what used to be Jimmy Messina's "Gateway" studio. It seized to be a studio in the '90's. The people who bought the building knocked some of the walls down, filled the spaces between the floating floors with concrete, walled over some of the doors and windows, and of course removed all the acoustic treatment. They also extended the next floor up, and in the process nicely coupled the roofs of the tracking room, one booth and the control room together. They also cut all the duct and power cabling :cen: It was a brilliant studio before, I tracked some sessions there with Dave Mason, Ginger Baker, Stevie Winwood etc. Always loved the rooms. Outside there are two gigantic transformers providing 1800 amps of beautifully clean and balanced power. I am doing the rooms one-by-one and am doing most of the work myself. I have one really good friend / builder who comes in when he can after his normal building job. We started with de-coupling the walls, removing the concrete poured in the spaces between the floating floors (took a week with a small pneumatic hand hammer, so not to damage the floors - major sore bruised hands!!!) Next we re-framed the vocal booth, mic locker and two sound locks between rooms, as you can see in the picture. I'm busy building a bass trap / service area for the main tracking room. In the enclosed picture you see: left bottom - window opening from tracking room to vocal booth. top left to right - the area in question. right bottom - door opening to sound-lock, gray door leads to mic locker. The wave pattern 2 x 4 frame in front of the trap will most likely be covered with 2 x 8 straw panels and open slots with acoustic cloth (straw panels: http://bit.ly/x8hYsq ) The trap size is 14' wide, 8' average deep (9' to 7' angle) and 9' high. It will contain a trough for the electrics leading to the control and machine rooms, one 10" flex duct run and one 12" flex duct run for A/C and heating. The ducts will run over the floor, with 2 x 10" ones going up to vents in the bordering editing suites upstairs My questions are: A. My straw panels are 2' wide, 1" thick, but can be trimmed down. The framing is 4' high on the right, 5' on the left. I can put the panels top and bottom leaving a gap in the center, or diagonal across the 14' width. Or use 4 x 8 panels and leave one gap at the top or bottom. What would be the best way to go? B. The back of the wall (purple) is 2 x 4 framing. The purple you see is QuietRock, an acoustic drywall with an STC rating of 72. On the other side is a layer of 1/2" soundboard, decoupled with Green Glue. I will test the transmission and will finish the other side most likely with 2 layers of 5/8" drywall. I am thinking of leaving the other three sides open, fill it with 3" Safe & Sound rockwool batt, held in place by open netting. The alternative would be to put the rockwool in and close the wall with more drywall. C. I would really appreciate John's input with the size and construction of the hangers. Any suggestions welcome!!

"On the other side is a layer of 1/2" soundboard, decoupled with Green Glue. " Well, first, welcome and looks like you have yer hands full, and must have lots of money to be buying quietrock :) Soundboard doesn't have much mass and is typically used in the effort to damp panels. Green glue specifically does not decouple, and I would wonder why you would want to decouple something that has so little mass. But GG is a viscoselastic damping material designed more to damp panels and raise the panels low frequency isolation properties by shearing. Generally, you would install the GG in-between mass panels, like the quiet rock, but I am not aware of any documents at greengluecompany.com that show data on this particular material. Also, while STC is a good rating for determining what we as human can hear or not hear (20Hz to 20kHz) it is not a good measurement system for wall assemblies that get below these numbers in the frequency spectrum that a human may not hear but a quality microphone can, or neighbors might experience. A better rating might be the OITC (out door indoor transmission class), but even better than all is the TL or transmission loss of the assembly, which is more concerned with sound and particularly at low frequency which is the area of most concern in a sound filled environment. Usually, it is better to get the guys here involved in the start of these projects, rather in the middle since we can be , how can I say this, opinionated about the facts that we know and the truths that we rely on in the dissemination of this information.

Hey Brien, Thank you very much for your response. I completely understand your comment and I agree that I have built something which potentially "double decouples", which could also mean that it could do the opposite of what was intended. However, in this case there is a reason. First of all I tried to get an answer on weather I should close the "inside" wall first or should fill it with rockwool and leave it open, which I would have preferred. I have basically answered that question with some testing. I am filing it with Rockwool and closing it with a single layer of 5/8 drywall on the inside (inside of the trapping area). On the other side of the wall, upstairs, will be three editing suites. We cannot have any sound leaking between the spaces. It is going to be: 5/8" drywall, 2 x 4 frame (dampened at the top), 3" Safe'n'Sound rockwool insulation, QuietRock, soundboard and 5/8" drywall. Of course without overlapping seams etc. My previous studio and the one I had before than were both "less then ideal" buildings. The last one really good in shape, but consisting of a single layer of 1/4" wooden siding on 6" framing. the only way I managed to soundproof that animal cost effectively was by using a sandwich of soundboard, 7/8" high density drywall, huge amounts of non hardening caulk (no green glue yet) and a layer of 5/8" drywall, with blown in cellulose as insulation. (see this forum - finished studio's - Sjoko's studio). With this project we will have some very interesting challenges ahead. First and foremost there will be three editing suites upstairs and a post production suite directly on top of the control room! And I agree with you that quietrock is way too expensive! But it works. Thanks for your comment!