Building bass traps

I know this has been talked about before but I could not find it doing a search. A friend of mine said you can build a bass trap by making an air tight plywood box filled with fiberglass any size as long as it's at least 8" deep. Is this correct?

I heard once before you need a small hole in it. I really don't know much about it, any ideas?

George Augspurger designed most of the rooms I worked in, and his traps always used peg-board. In fact, the whole rear wall in one of our control rooms was peg-board about 12" away from the orignal concrete block walls. The peg-board was covered with porous material, much like a furniture covering or something, and the airspace between the peg-board and concrete wall was filled with fiberglass.



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ERIC SEABERG • San Diego, CA
eseaberg@home.com

Eric, what exactly is peg - board? Is that another name for partical board?

So in theroy, the low frequency waves penetrate the boxed in space filled with fiberglass and are traped?

I am about to build a trap myself. And I also have different questions:
- How important is it to to find the right resonance frequency of the room? Doesen`t it make it worser if I absorb the wrong frequency?
- To find out wether I need to build a Trap or not I thought about tests with a open window. Is this a silly idea or does a open window/door act like a Basstrap?
- I ve heard about fiberglass is bad for health (cancer). Are there some substitute materials that I can get in Europe.

Reto

Pegboard is a 4x8 sheet with 1/8" holes in it every square inch... you know it's the stuff that holds hooks so Tim Allen can hang all of his tools on it in the garage!!

Build-out a frame of 1x1 about 9-12" from your wall. Tack 6" or more of insulation on the original wall and nail the pegboard to the framing. Cover it with any porous material you may like. I'd also recommend NOT building it all the way up to your ceiling... leave about a 1-foot space up there. This really makes a difference, but the fiberglass should only go as high as the pegboard... mainly so you can't see it.

If you don't want to use fiberglass, then you can spend a lot of money for some of the foam products.



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ERIC SEABERG • San Diego, CA
eseaberg@home.com

Hello all
Check out http://www.ethanwiner.com/basstrap.html http://www.studiotips.com/ http://ic.net/~jtgale/diy2.htm
AES NYC There will be a workshop " GUERRILLA ACOUSTICS III " PERSPECTIVES ON ACOUSTICAL REQUIREMENTS FOR SMALL ROOMS WITH AN EMPHASIS ON PROJECT STUDIOS.
It will held on Sunday Sept. 23 @ 9.00 AM, $35.00 Workshop fee.
Hope this helps Good Luck VU

Hey all.... Check out www.decware.com and look under acoustics they have a bass trap plan that rocks!!!! absorbs all the way down to 25 weighs a ton but is easy to build and works well. good luck.

Hey y'all -

Definitely pick up copies of F. Alton Everest's books on acoustics:

• The Master Handbook of Acoustics (the latest edition rocks)
• Sound Studio Contruction on a Budget
• Build a Small Budget Recording Studio From Scratch

All this stuff is covered. Deep stuff, but great reference books. I'm also very interested in Dave Moulton's ideas, but haven't the space that he has to try any of it. Nick can probably give more and better detail on his theories.

From what I know, yes, it makes a big difference what frequencies you target and why...Everest goes into a lot of detail on tuning Helmholtz resonators (either slat or pegboard-style holes) as well as other methods of treatment, and how to get the appropriate degree of absorption at the right frequencies. I wouldn't want to guess at this - it's the sort of thing that should be measured first. Fortunately, the lastest edition of Master Handbook of Acoustics has a chapter on measurement written by Doug Plumb of Acoustisoft (which makes ETF, a great, low-cost acoustics measurement program).

There's also an acoustics mailing list that's quite good, and geared towards smaller recording studios. The site's http://www.studiotips.com/ , and the list is hosted by Yahoo/Egroups.


charlie

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charlie bonnell
www.copperdalton.com

[This message has been edited by CopperDalton (edited 09-08-2001).]

Eric, so your saying build a frame, lets say 4 ft across, 4 ft tall and 18" deep, fill it with fiberglass and cover the frame with peg board? Thats interesting because of the other way was to have an air tight box filled with fiber glass. I guess they would both work, I don't know.

I just need to loose the low end of a kick drum that fills my room whenever i'm tracking a band.

The frequency will depend on the depth of the absorber, so 12" vs 18" will make a difference.

A sealed box works IF you use thin material, so that it actually squeezes by the bass sound pressure. You can also make bass traps by this method, just creating shallow, sealed boxes against your walls. They flex when hit by bass.

Blue, if you don't know what freq to absorb, you can't do anything. First find out what freq you want to get rid of. Then find out what to build.

OOOOOOOhhhhh! BASS TRAPS. I thought everybody had a lot of spare time and was going fishing! My Bad.

Bill Corkery

In a sealed box, the front panel acts as a resonator that traps/cancels it's tuned frequency. The resonant frequency is dependent on the volume of air space in the box, and the thickness of the front panel. Being rather frequency specific and narrow bandwidth, the resonator traps are good if you have measured/calculated to know what frequencies you're going after. If you're not sure, they can do more harm than good, though it's pretty safe to say that smaller rooms will need a lot of help in the low frequency area.

The pegboard faced box will be sort of like a Helmholtz resonator (a box with slats or ports tuned to very specific frequencies), a panel resonator, and a porous absorber (that traps sound waves and converts them into heat). These with their wider bandwidth, are not as effective at specific frequencies as the resonators, but are a good general treatment that covers a wide range. I like to put a curved (poly cylindrical) face on these to add diffusion to the equation, while also blending the "box" into the wall nicely. Here's a couple of poly diffusers that I made (mainly for diffusion, not bass control) for the control room.

PLEASE note, that I'm just interpreting stuff that I've read and been told, and am by no means an expert in this area. In other words, I just might be talking out my arse (among friends though).

A better version (though much more of a pain to build) of DIY tube traps is at Jon Risch's site. This cat knows his shit. I made these with hi-loft polyester batting, 'cause I don't dig fiberglass, and they work great. If you make Gale's pipe insul ones, go with 2" thick instead of the 1" he calls for. And if you hate fiberglass like me, cover it with thin (.5 mil or less) plastic sheet to contain the fibers. Then, before covering with fabric, wrap some poly batting (maybe .5 inches thick) around it to re-gain some of the hf absorbtion that the plastic took away (unless you want the HF diffusion).

Thanks alot guys for so much good information. I have a better understanding of what are and how bass traps work.

My room is small with low ceilings so when I have a drummer in here the kick fills the room. I just want to tame some of that.

I think what I well do is build several resonator type bass traps different sizes. This way may help to cover more low frequency's.

This is more for the sake of recording and not mixing. As of now, the mixes translate pretty good to other playback systems as far as the low end goes. I just want to clean up the room and not have to clean it up with EQ.

Jeremy,

Here's an interesting thread about using a kick drum tunnel , which may help you in your quest for kick drum isolation.

You guys are great! The timing is great cuz I'm doing my sound room now.

I'm not looking into instructions on how to build a Babe-Trap. I know you can do it with a Ferrari or a cool mill or so in the bank but what about the do it yourselfers?


/Ricache