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 Post subject: idea for broadband gobos
PostPosted: Tue Feb 14, 2006 1:18 pm 
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I have an idea for something I'm calling (for now) "broadband gobos" that I wanted to run by this forum. I want these units to be versatile, freestanding units with a reflective side and an absorptive side, with the absorption capable of going well into the low end to provide some bass-trapping benefit if they are placed correctly.

The idea is to make a wooden frame out of 2x8s that is 2' wide and as tall as you want the gobo to be. Put plywood on one side of the gobo to create a reflective surface, and a 4" layer of 703, rockwool, or cotton covered in fabric on the other side to create an absorptive surface, such that there is a 4" airspace on the inside of the gobo between the plywood and the back of the absorptive material.

So finally my question: Would this design help the gobo absorb more low end than if they were simply 4" thick, build the same way without the airspace? I know that when you mount panels of 703 on walls you are supposed to space them for better low end absorption.

Some background information: My studio is a one-room basement studio, 15x17x8 with 2 concrete walls and 2 framed/sheetrock walls, that is as much "rehearsal space" as "recording studio." I'm also planning to build corner bass traps along the wall/ceiling and wall/wall corners, as well as pack 12" of fluffy fiberglass in the ceiling joists.

My room is small and mulitpurpose, and it will most likely move someday, therefore any acoustic treatments I build have to be versatile. I'm planning on building about a dozen of these units, so they can be moved around my studio for recording, and placed strategically along the walls during mixing/critical listening to create a RFZ at the listening position. I'm basically riffing on the idea that "you can't have too much bass trapping in small rooms," and trying to eke out a little more bass trapping out of my multipurpose gobos.

I also know that room placement will play a large part in how much low end they absorb; I'll be most interested in their low-end absorption when they are placed along the walls. Or possibly when arranged around the drum kit. 8)


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PostPosted: Tue Feb 14, 2006 1:25 pm 
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The determining factor is the size of the gobo in relation to the wavelengths of the frequencies being isolated. Where the wavelenghts are larger that the dimensions of gobo, no additional gain is achieved.

With that said, yes what you descrivbed will increase the low end absorption for the relevant wavelengths.

Andre


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PostPosted: Tue Feb 14, 2006 1:55 pm 
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So if these are 2' wide, they will only be effective down to 2' wavelengths, which is about 565Hz-ish?

Is that because they are sealed units, as opposed to the open back of 703 panels straddling corners? Hmm....


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PostPosted: Wed Feb 15, 2006 12:43 am 
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You got the idea. Not because of what they are from, but because of physics of diffraction. At lower wavelengths the sound just goes arouind the panel. Of course there is still some effect as it is not a hard point but rather a broad effect that takes place.

Andre


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PostPosted: Sat Aug 01, 2015 9:29 pm 
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Thank you informed me.


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PostPosted: Mon Oct 26, 2015 2:38 am 
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Thank you informed me.


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