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Author Topic: Plastic bags of fiberglass as Bass traps????  (Read 2789 times)

zmix

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Plastic bags of fiberglass as Bass traps????
« on: January 27, 2007, 01:01:51 pm »

An artist I work with told me that a studio near him uses plastic bags of fiberglass as bass traps. They are simply buying bags of household insulation straight from the local building supply and then piling up the bags in corners. I've been thinking a lot about this one. The sealed bags wouldn't affect the high end much, perhaps adding some diffusion, but the low frequencies would pass through.

Anyone want to test this idea?

jimmyjazz

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Re: Plastic bags of fiberglass as Bass traps????
« Reply #1 on: January 27, 2007, 03:57:05 pm »

It works.  It's ugly as hell, but it works.  I actually think the lack of attentuation at the highest frequencies has some benefit, because plenty of rooms have decent absorption in the higher frequencies due to carpet, upholstery, etc., and mainly need help in the bass region.  When thick absorptive panels are used to help reduce low frequency room modes, they also further attentuate the middle and high frequencies, which may not be desirable.
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Gold

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Re: Plastic bags of fiberglass as Bass traps????
« Reply #2 on: January 28, 2007, 02:41:47 pm »

I just did this and it worked very well. I hung 2" batts of Thermafiber SAFB 2" away from the wall in garbage bags. I hung fabric in front of them like a curtain. For bass trapping I just piled four unopened packages in the most effective positions. I wrapped fabric around them. The packages are 4'x2'x16". The 2' dimention could change as they come in different widths. I also stuffed a cabinet that was hung from the high ceiling full of the stuff and covered it in fabric. If I was going for ad clients the finnishing would have to be a little nicer but the room sounds good down to 50hz or so. I need some more bails of the stuff to make the very low end better, but it's better than a lot of rooms I've been in. The room is only 200sf so I'm happy (and working). I'm in Greenpoint if you want to come by.

The question I have for the experts is. Is it less efficient to leave the batts under pressure in the bag? I would guess yes because it would take more pressure to make the fibers vibrate. But a lot of this stuff is counter intuitive.


EDIT: It might be of intrest that I hung the batts first. Then I went to work on the equipment restoration/installation. Since the room is small I knew I wouldn't be able to do any listening until the equipmentwas in place. I always float my speakers in sandboxes. I wanted that done before I listened.  The low end was really awful. It sounded like the excel spreadsheet looked. So I got the four packages of SAFB, which is the amount I used for the rest of the room. It was pretty amazing. I ended up putting two, long way vertical, behind the speakers in the corners. The other two I layed between the speakers, long way on the ground, one on top of the other. It worked better than puting them on top of the other ones in the corner. Go figure?The high end did suffer a bit so I  took a piece of double wall corrugated plastic sheet and bent it at the top corners with a piece of wire. The shape is rounded and irregular because the bend radius is smaller at the top. I put this on top of the packages between and behind the plane of the front of the speakers. That worked a treat too.
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franman

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Re: Plastic bags of fiberglass as Bass traps????
« Reply #3 on: January 28, 2007, 03:15:09 pm »

I would have to say yes, you are sacrificing some efficiency with the insulation in the bag, but as you've noted, it does work...In deep bass traps we typically "hang" the batts so they are free to 'vibrate' easily... Twisted Evil
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