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Author Topic: 'Ventilating' modal pressure in a control room?  (Read 2041 times)

widrace

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'Ventilating' modal pressure in a control room?
« on: June 03, 2009, 03:22:37 pm »

Here's a new one...

Is it possible to release the modal pressure to good affect by providing a pressure escape path? The basic idea is to cut openings in the corners, etc. allowing release to the outside world.

My control room shell is 2 layers of 5/8 gypsum on R-channel. The RC is on 2x4 studs (std insulation) with 1/2 OSB on the outside. Vinyl siding after that. The room is about the size of Gateway.

No neighbors so leakage in either direction is a non-issue around here. Comments?

Ethan.....please refrain
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jimmyjazz

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Re: 'Ventilating' modal pressure in a control room?
« Reply #1 on: June 04, 2009, 10:54:58 am »

My gut tells me that you could encounter a variety of problems, including (but not limited to) diffraction and wind noise.  Furthermore, I would also think that the efficacy of such a vent might be a function of its size.  Think wavelength -- would a 1 meter hole be "visible" to a mode with a wavelength of 7m (~ 50 Hz)?

The theory should be fairly easy to test in a standard control room.  Measure room response at various locations with and without the human entry door open.  In my own experience, I know that low frequency response at the mix position can be affected somewhat by whether or not that door is open, but I've always attributed it to being related to a rather dramatic change in room "geometry" (which is in a sense what you are proposing).

I'm curious to hear others' thoughts.
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Greg Reierson

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Re: 'Ventilating' modal pressure in a control room?
« Reply #2 on: June 04, 2009, 12:32:35 pm »

I asked that question at a acoustics panel at the SF AES. A couple of the panelists though it was an intriguing idea but they have to deal with isolation so it's a non-starter 90% of the time. Otherwise, yes, they said it could provide a benefit in the right conditions.

My studio has a relatively porous back wall in the <150Hz range. That works as well as any bass trap as long as you don't have to worry about sound getting in or out. Doors are not usually located in a good spot to test the idea but it's work looking at.


GR
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mike shelton

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Re: 'Ventilating' modal pressure in a control room?
« Reply #3 on: June 04, 2009, 12:40:06 pm »

I think I remember reading about a few studios built in the 90's that were flat down to something like 10Hz. They acomplished this by venting the rooms into larger "attic spaces" that were acoustically coupled to the studio space. It let the bass waves "see" a larger space.

I used this same concept in a night club I designed, where we vented the dance floor area into an attic space that acted as a huge bass trap...
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Eric H.

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Re: 'Ventilating' modal pressure in a control room?
« Reply #4 on: June 04, 2009, 05:54:23 pm »

Electrical audio's alcatraz room is also based on that principle i think. It gives a quite intriguing space impression. Or i am totally wrong?
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eric harizanos

Greg Reierson

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Re: 'Ventilating' modal pressure in a control room?
« Reply #5 on: June 04, 2009, 07:11:06 pm »

Any open floor plan, such as in a house, works this way.


GR
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Thomas Jouanjean

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Re: 'Ventilating' modal pressure in a control room?
« Reply #6 on: June 05, 2009, 03:02:59 am »

widrace wrote on Wed, 03 June 2009 14:22

Here's a new one...

Is it possible to release the modal pressure to good affect by providing a pressure escape path? The basic idea is to cut openings in the corners, etc. allowing release to the outside world.

My control room shell is 2 layers of 5/8 gypsum on R-channel. The RC is on 2x4 studs (std insulation) with 1/2 OSB on the outside. Vinyl siding after that. The room is about the size of Gateway.

No neighbors so leakage in either direction is a non-issue around here. Comments?



1 square meter of 100 % absorbing material has an absorption of 1 square meter of open window according to Mr Sabine Smile

Having holes leading straight to the outside isn't realistic though because of all the problems it would lead to (noise to start with) so you'd need the room 'ports' to vent into another closed space. You'd have to treat that space in such way that it won't start interacting back with your room, therefore treat it with absorption...

So you're back with a (pbly big) bass trap, albeit an exotic type.
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Thomas Jouanjean
Northward Acoustics - Engineering and Designs
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widrace

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Re: 'Ventilating' modal pressure in a control room?
« Reply #7 on: June 05, 2009, 03:14:51 pm »

Thank you for your comments gentlemen.

Funny you should mention exotic...

Attached is a pic of a (pbly big) bass trap from inside of it.  A second pic is in a follow up post, which is a shot of the rear wall that it is exposed to. The opening is behind, and somewhat larger than the black fabric area. It is the full width of the room, about 4 feet high in the center, reducing to 2' at each side and is 13' deep.

About 5' behind the blue modular absorb wall are a pair of 6' doorwalls (back-to-back) for entry from a lounge/vocal/dub room that is 13' deep as well. The trap is above this room.

I have experimented with its 'operation' quite a bit. At one time or another, it's been filled with either fluffy fiberglass rolls, cellulose (still in the bags) or about 80 of those modular absorbers. They all worked quite well, and prevented a return to the main room. Will probably put the cellulose bags back in, as that was the cleanest, most adjustable filler. The only thing left to my imagination would be to build the worlds' deepest diffusor into it. How about that one?


index.php/fa/12497/0/
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widrace

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Re: 'Ventilating' modal pressure in a control room?
« Reply #8 on: June 05, 2009, 03:22:08 pm »

To repeat...this is a shot of the rear wall that the trap is exposed to. The opening is behind, and somewhat larger than the black fabric area. It is the full width of the room, about 4 feet high in the center, reducing to 2' at each side and is 13' deep.

About 5' behind the blue modular absorb wall are a pair of 6' doorwalls (back-to-back) for entry from a lounge/vocal/dub room that is 13' deep as well. The trap is above this room.

I have experimented with its 'operation' quite a bit. At one time or another, it's been filled with either fluffy fiberglass rolls, cellulose (still in the bags) or about 80 of those modular absorbers. They all worked quite well, and prevented a return to the main room. Will probably put the cellulose bags back in, as that was the cleanest, most adjustable filler. The only thing left to my imagination would be to build the worlds' deepest diffusor into it. How about that one?

index.php/fa/12501/0/



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Thomas Jouanjean

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Re: 'Ventilating' modal pressure in a control room?
« Reply #9 on: June 10, 2009, 03:39:56 pm »

widrace wrote on Fri, 05 June 2009 14:14

Thank you for your comments gentlemen.

Funny you should mention exotic...

Attached is a pic of a (pbly big) bass trap from inside of it.  A second pic is in a follow up post, which is a shot of the rear wall that it is exposed to. The opening is behind, and somewhat larger than the black fabric area. It is the full width of the room, about 4 feet high in the center, reducing to 2' at each side and is 13' deep.

About 5' behind the blue modular absorb wall are a pair of 6' doorwalls (back-to-back) for entry from a lounge/vocal/dub room that is 13' deep as well. The trap is above this room.

I have experimented with its 'operation' quite a bit. At one time or another, it's been filled with either fluffy fiberglass rolls, cellulose (still in the bags) or about 80 of those modular absorbers. They all worked quite well, and prevented a return to the main room. Will probably put the cellulose bags back in, as that was the cleanest, most adjustable filler. The only thing left to my imagination would be to build the worlds' deepest diffusor into it. How about that one?



Nice! It must've been a lot of work to build on your own... (?)

Using the space "between" the shells is a rather common tool for deep-bass trapping. It's very efficient, although not always very easy to manage.

Smile
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Thomas Jouanjean
Northward Acoustics - Engineering and Designs
http://www.northwardacoustics.com
http://www.facebook.com/pages/Northward-Acoustics/1062876633 71

Pro Audio Partners:
ATC Loudspeakers
FOCAL Professional Speakers
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