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Jon Nolan
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room inside a room

Post by Jon Nolan » Mon Aug 05, 2013 7:11 am

regarding the distance seperating the two walls (exterior & interior studio wall)....

i'm trying to conserve space, and an inside out wall (sayers) isn't a possibility. can i set up my interior wall with a 1" gap, or is that not worth it at that point? i remember reading somewhere that it should be at least 3", but im wondering what it means in actual loss of STL.

thoughts?

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jhbrandt
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Post by jhbrandt » Mon Aug 05, 2013 8:13 am

Jon,

The quality of isolation using decoupled partitions is governed by the mass of the partitions and the air space + absorption IN the air space.

When you cut either the mass or air space in half, generally, you will loose about 5dB on the single number scale. What is NOT mentioned is the loss of usability at LOW FREQUENCIES when mass or air space is compromised. This is because it is a resonant system and a smaller air space or lower mass RAISES the resonance of the system. As a result, the LF STL suffers.

I do not recommend the inside-out wall approach unless special circumstances are involved. These type of walls are usually used by people because they THINK that they can have less air space or it will save them room.. whatever. But that is NOT true. It's just a trickey way to build an isolation wall - very difficult to do & really NOt worth the trouble in my honest opinion.

There have to be good reasons for doing something like that. As a builder, I would need some serious convincing. ;)

Cheers,
John
John H. Brandt - Recording Studio, Performance Hall & Architectural Acoustics Consultants
http://www.jhbrandt.net

"Twenty thousand dollars worth of Snap-On tools does not make you a Professional Diesel Mechanic"

Ron Obvious
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Post by Ron Obvious » Mon Aug 05, 2013 8:50 am

Hello Jon,

a 1" space is more than enough. The most important factor is that the two walls never touch each other. Think building shift?? Secondly, I make the two walls out of different materials to produce different self resonant points for each wall. So on the existing gyprock wall add 1/2" rigid fiberglass panels or Donacona. I'm assuming that this wall has insulation in it.

Key points - mass and separation.

The inner walls would now ideally be made with 2x4 studs or metal. Also space the studs apart 24" centres for a lower STC, over 16" centres. First clad outside with gyprock. Now lift and place all four walls leaving enough room at the top to put your isolated ceiling joists, as part of your isolated room. The only 'common' surface is the floor. To isolate that would cost [ALOT]. I.E. true room within a room. For now the floor would be carpeted except in front of the console so that you can move your chair around.

I personally would always angle these inner walls slightly (3 to 5 degrees) to help with early reflection bounces. Think of a movie theatre. Your speakers & work surface at the front. side walls moving away from you slightly. Back and front wall can be parallel, however if you can put a couple of symmetrical angles at the back, that would be great. Maybe add some AC boxes for some nice wall sconce lighting.

Fill the inner walls with ROXUL Safe & Sound. Next 5/8" plywood. Make sure it's all sealed properly with couching. Last 5/8" gyprock. Everything should be glued and screwed NO NAILS! Another advantage of the 5/8" plywood is that you can now screw baffles anywhere, on any walls, as you do the final "tuning" of the room. You now also have to do this with the ceiling. Slight angle if possible again. Leave enough room up there for any lights and VENT DUCTING.

Make sure you have proper ventilation to get rid of the 'stale air' in the room other wise your clients will not come back!!! This would be very quiet bathroom vent fan mounted to the outside wall of your house. It's switched on when you turn on the lights in the control room. Next a long insulated vent hose with some deliberate curves in it, to a point somewhere above the console/human, to suck out the hot-bad-old air. This can be hidden behind the 'baffle' cloud over the console. New fresh air comes in through the studio door when you open it. This is of course assuming this is a 'home-studio'. If you're building a full-on one, you would have a low noise HVAC system installed > $$$.

All AC sockets in the room should be on the same (15 amp) circuit. Put all the lights, etc on another. Most modern home studios can run all audio equipment on one circuit. If not add a second one but make sure it's on the same 120v phase in your fuse panel.

Save some money for building acoustic panels, or buying heavy fabric carpets or curtains to 'fine-tune' the room when you are finished and have all your gear and furniture in there.

Remember a 'control room' should be representation of the 'average tone' of all the living rooms in the world. NOT a flat 20-20k - perfect space ship, with no vibe!

See my C.V. I've built a few "real studios"
http://www.mts.net/~lakemail/bio-cv.html

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jhbrandt
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Post by jhbrandt » Mon Aug 05, 2013 7:33 pm

Ron,

Sorry to be contrary, but what do you mean, "a 1" space is more than enough."? More than enough for what? - building shift? That's fine. BUT - It's definitely not enough to isolate 80Hz. Most of our rooms isolate to 20Hz. You must understand the fundamentals of MAM (mass-air-mass) resonance. Remember that air is a spring too and must be added into the equation.

Also different materials bonded together as in one wall panel do NOT resonate at different frequencies. - The combined mass on the 'spring' of air space resonate. Ideally, one would make the two decoupled partitions of different masses so that their resonant frequencies do not coincide. THIS technique usually improves STL, however if the coincidence resonance of the panels is BELOW the frequency of interest, it matters little.

Ron, please don't get me wrong, I agree with your other points and suggestions, except - unless you are allergic, use regular R19 type fiberglass for cavity fill (better STL) & don't use plywood unless you need shear support. Gypsum board is higher mass and that is all you need there for isolation. ALTHOUGH, I really like your idea that you can place baffles anywhere... Great Idea. I would still add another layer of 5/8" drywall. :) - But that depends on the STL requirement.

I do rooms a bit differently. I have never found that angling the enclosure shell helps with modal distribution & can often make predetermination impossible. All of our studio builds have never needed acoustic adjustment after they are built and installed per plan. - There you have it. - No fine tuning necessary. ;) Rectangles rule! hehe.

I hope this helps. I am careful to offer "opinions", but rather offer facts. - And I always have testing data to back up the things that I discuss here.

We should get together sometime. My Skype ID is jhbrandt3.

Cheers,
John
John H. Brandt - Recording Studio, Performance Hall & Architectural Acoustics Consultants
http://www.jhbrandt.net

"Twenty thousand dollars worth of Snap-On tools does not make you a Professional Diesel Mechanic"

MoreSpaceEcho
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Post by MoreSpaceEcho » Thu Aug 08, 2013 8:18 am

hey jon,

a 1" gap is fine, because you can count the depth of the interior wall studs as part of the gap. so it's really more like 4.5".

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roscoenyc
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Post by roscoenyc » Fri Aug 09, 2013 6:37 am

Jon,
as a friend I'd urge you to buy Rod's book. There is so much helpful info inside. I can't stress it enough.

http://www.amazon.com/Home-Recording-St ... 143545717X

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Jon Nolan
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Post by Jon Nolan » Fri Aug 09, 2013 6:51 am

roscoenyc wrote:Jon,
as a friend I'd urge you to buy Rod's book. There is so much helpful info inside. I can't stress it enough.

http://www.amazon.com/Home-Recording-St ... 143545717X
Thx brother. I have had it for some years now. An amazing and helpful book.

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roscoenyc
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Post by roscoenyc » Fri Aug 09, 2013 10:45 am

Jon Nolan wrote:
roscoenyc wrote:Jon,
as a friend I'd urge you to buy Rod's book. There is so much helpful info inside. I can't stress it enough.

http://www.amazon.com/Home-Recording-St ... 143545717X
Thx brother. I have had it for some years now. An amazing and helpful book.
Cool, I was about to offer you my personal money back gaurauntee:)

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jhbrandt
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Post by jhbrandt » Thu Aug 22, 2013 10:48 pm

Guys,

I just posted a new paper on my site which you all may find helpful. :)

http://jhbrandt.net/Sound-Proofing-The-Quest.pdf

Cheers,
John
John H. Brandt - Recording Studio, Performance Hall & Architectural Acoustics Consultants
http://www.jhbrandt.net

"Twenty thousand dollars worth of Snap-On tools does not make you a Professional Diesel Mechanic"

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