#966258 - 07/06/01 02:43 PM
To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Registered: 01/28/01
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Ethan,
My bass traps are finally in process. I started with two deep traps and two high bass traps, and I should be finished by the weekend. I am going to place them against the back wall, and hopefully eliminate the standing waves. I am then going to build about ten more (a mixture of deep, high, and mid/hi absorbers), depending on the success of the first units.
The traps are identical to your design, but instead of being mounted to the wall, they are mounted to a sheet of 3/4" AC Plywood and a sheet of 3/4" particle board. The backings are held together by fifty to sixty 1-1/4" drywall screws, and the 2"x2"s are secured to the backings with six 2-1/2" drywall screws. Needless to say, these are some heavy traps. So heavy that I wonder if their performance could be compromised.
I do have a couple of quick questions:
1) Is the effectiveness of the traps (particularly the deep traps) dependent on volume? I have a tough time explaining to people that bass frequencies will vibrate the 1/4" plywood (at normal listening levels), but the volume is at least significant enough to create standing waves.
2) Is there another fabric I could use for the mid/hi absorbers other than burlap? The #703 fiberglass sheds a lot of small fibers, and I'm concerned that they will get past the burlap. Is there a tighter woven fabric that I could use that won't compromise effectiveness? Perhaps cotton?
3) Real estate is becoming a constraint. I have two ideas to minimize the impact, and I want to get your feedback:
a) Mini Traps
There are two areas where I can't fit a 24" wide trap, so I am considering a 12" wide trap (still 8' tall). They would be placed behind the front wall, where my monitors are. Your thoughts on effectiveness?
b) Dual Traps
I thought about putting a combination deep/hi bass trap in two corners of the room (the corners that join the front and side walls). This dual trap would share a 2'x8' plywood/particle board backing, but the top 2'x4' section would be a high bass trap, and the bottom 2'x4' section would be a deep trap. It would save some money, and since I have to continually move one of the traps to get in and out of the room, it might be more convenient. Your thoughts?
Anyways, thanks again for the help. I'll let you know how the first four units turn out.
All the best,
Wiggum
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#966259 - 07/06/01 04:04 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Ethan Winer
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Registered: 06/12/00
Posts: 5391
Loc: New Milford, CT, USA
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Wiggum,
> The backings are held together by fifty to sixty 1-1/4" drywall screws ... <
There you go! Running a bunch of "Jackson Pollack" beads of glue between the boards will help further.
> So heavy that I wonder if their performance could be compromised. <
Not at all. The heavier - or more accurately, the less flexible - the better.
> Is the effectiveness of the traps (particularly the deep traps) dependent on volume? <
You mean audio volume, not cubic feet volume, right? Any bass trap will work at both low and high volumes. The wood may not vibrate visibly, but it's still vibrating. If you touch the panel with your hand while music is playing you'll feel the wood vibrate. That proves it's working, and you should be able to feel the vibration even at fairly low levels.
> Is there another fabric I could use for the mid/hi absorbers other than burlap? ... Perhaps cotton? <
Any soft fabric will be fine. Shiny fabric with a "hard" surface will reflect the highest frequencies so stay away from those.
> I am considering a 12" wide trap
That will double the range of frequencies absorbed, so a trap that size will not be as effective at trapping bass.
> the top 2'x4' section would be a high bass trap, and the bottom 2'x4' section would be a deep trap. <
Without actually building one and testing it, I again have to assume this is not a good idea because it changes the range of frequencies that will be absorbed.
--Ethan
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#966260 - 07/06/01 08:20 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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alphajerk
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ethan, can you send me a link or email to the designs. im quite curious.
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alphajerk FATcompilation "if god is truly just, i tremble for the fate of my country" -thomas jefferson
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#966261 - 07/07/01 01:14 AM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Thanks Ethan,
I am going to try a thin, woven cotton for the high absorbers. I am also going to wrap some raw #703 and hang the tiles like pictures. It will be some time before I can build the actual mid/hi absorbers, and I think the #703 panels will help nix the flutter echo.
I will stay away from the dual and mini idea. If need be, I can pursue some alternate treatments on the problematic wall (perhaps some foam diffusers or some deep wedges).
I may have a problem with my traps.....
When I made the 1.5" backings, I thought about laying some Liquid Nails between the sheets, along with the screws. I wound up just using screws. I laid a trap frame on the saw horses this afternoon (a backing with the end frames, but no fiberglass or plywood cover), and I slapped my hand against the backing. To my surprise, the boards vibrated for perhaps 1 - 1.5 seconds. I didn't hit it really hard, I just gave it a thud from my palm.
I don't know if this is cause for alarm or not. I don't know how I could have made these traps any more rigid. Everyone who has seen them has walked away laughing. They just can't believe how heavy they are.
I am going to try to shoot some additional screws along the edges, and hopefully dampen the vibration. BUT, the traps won't be in the same orientation when placed against the wall, so maybe there is nothing to worry about. If all else fails, I guess I could laminate another sheet of plywood to the backing, but I'll need three people to lift the trap.
I just hope it has nothing to do with my choice of materials (3/4" ply and 3/4" particle board). That particle board has got me nervous. At this point, it would be VERY difficult to remove it and replace it with a different material. But I sure don't want to make my room more boomy than it already is.
Alphajerk: You can find the article at:
http://www.ethanwiner.com/basstrap.html
Thanks again,
Wiggum
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#966262 - 07/07/01 02:38 AM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Ethan Winer
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Registered: 06/12/00
Posts: 5391
Loc: New Milford, CT, USA
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Wiggum,
> I am also going to wrap some raw #703 and hang the tiles like pictures. <
That will do nicely.
> the boards vibrated for perhaps 1 - 1.5 seconds. <
I think that's fine. The self-resonant frequency sounds like it's probably around 0.5 Hz.  which is a good thing!
> I am going to try to shoot some additional screws along the edges, and hopefully dampen the vibration. <
As long as the two pieces aren't buzzing, you probably have enough screws. That was the only reason I suggested also using glue. Glue is needed when joining two pieces of plywood for a floating floor, to prevent it from squeaking as you walk. It's probably not needed here.
> BUT, the traps won't be in the same orientation when placed against the wall, so maybe there is nothing to worry about. <
Probably not. With one edge on the floor, that should keep it steady.
> Alphajerk: You can find the article at ... <
Thanks.
--Ethan
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#966263 - 07/07/01 03:31 AM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Thanks again Ethan...
I may or may not shoot the additional screws. At the very least, if I run into a problem, I know I can always lay another backing over what I have. If the resonant vibration is less than 20 Hz, the traps can vibrate all they want .
I'll send you photos of these bad boys when they're done. My neighbors don't know what the heck I'm doing, but its fun to watch their faces when I try to explain .
Thanks again,
Wiggum
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#966264 - 07/07/01 05:57 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Ethan,
I have one more question for you....
How significant is paint? I initially planned to stain the traps, but I'm leaning toward paint. I will need to lay a coat of primer (latex), and 1-2 coats of paint. I imagine the end frames are insignificant, but the vibrating surface concerns me. With the primer, that's three coats of paint (satin or semi-gloss latex).
Please advise if you see an issue - thanks again.
Wiggum
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#966265 - 07/07/01 08:26 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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c1131@hotmail.com
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Registered: 06/10/00
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Loc: Adrian,MI,UNITED STATES
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Hello, where did you guys get you #703 I have talked to lots of people including Owens Corning and I cant seem to find anyone who can get me this stuff ( or 704 ) I have called all the local commercial insulation places and no one wants to deal with with me. Sound Sanctuary Studio off of this forum was kind enough to give me the number of the person he bought it through in Cali and that guy wouldn't call me back. Where did you guys find it ? I am willing to have it shipped. I live in Michigan. I have seriously called everyone here, from insulation contractors to home theatre contracters to a company that builds movie theatre's as well as the suppliers Owens told me to call and still no luck. thanks for any help.
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#966266 - 07/07/01 08:32 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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alphajerk
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is 703 that stuff that is a "board" of pressed insulation? why does NO ONE CARRY IT for civilians, and those who do carry it will ONLY deal with contractors? thats pretty fucked up. fortunately my father in law is a contractor and has an account at a HVAC place that carries it. it is primarily used for ductwork to silence the plenums.
_________________________
alphajerk FATcompilation "if god is truly just, i tremble for the fate of my country" -thomas jefferson
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#966267 - 07/08/01 01:46 AM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Registered: 01/28/01
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Indeed, Owens #703 is a pressed fiberglass insulation. It is popular with audio folks because you get a lot of absorption for a very narrow thickness.
It is hard to find, but a professional insulation store can sell it to you. Forget Home Depot and the like -- they don't even know what it is. As for the "contractor attitude"...yeah, I have encountered that myself, but eventually you will find a place willing to sell it to you. Why wouldn't they want your money?
You might want to try an acoustics design firm (the guys who design and build professional studios and broadcast rooms). If your local insulation contractors are truly that lousy, these folks should be able to tell you where to go.
All the best,
Wiggum
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#966268 - 07/08/01 02:55 PM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Ethan Winer
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Registered: 06/12/00
Posts: 5391
Loc: New Milford, CT, USA
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Wiggum,
> I'll send you photos of these bad boys when they're done. <
Yes, please do!
> How significant is paint?
Not at all. The mass of one or two coats of paint is 1% or less the mass of the wood, and so will not be a factor.
--Ethan
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#966269 - 07/09/01 01:32 AM
Re: To Ethan Winer: My bass traps are in progress - a couple of quick questions...
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Wiggum
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Posts: 428
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Ethan,
This may sound like a dumb question, but does the sheen of the paint make a difference? You had mentioned in a previous post to stay away from shiny fabrics (for the mid/hi absorbers), but I assume this was due to the porosity and composition of the fabric, rather than the sheen.
I have decided on a black cabinet (semi gloss or gloss), and an oak / polyurethane face (gloss).
I will be attaching the plywood faces tomorrow, and hopefully have the traps in my studio by next weekend. I'll let you know how they sound.
Thanks again,
Wiggum
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