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Jon Risch bass trap fabric choices?

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Aaron 01

(A)

I took the time to build a pair of J R bass traps as per his instructions. They are 4 ft. tall (actually a hair over about49") and now I am having trouble finding burlap over 48" wide to cover these. I did find this hairless linen, burlap type material locally that looks nice and is wide enough, but I wonder if this is as good as the regular burlap for acoustic transparency? I am almost thinking of just ordering the Guilford and being done with it. Any thoughts on the hairless linen burlap?

http://www.denverfabrics.com/Merchant2/merchant.mvc?Screen=PROD&Store_Code=001&Product_Code=23199&Product_Count=&Category_Code= (Open in New Window)

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Re: Jon Risch bass trap fabric choices? - Jon Risch 19:51:30 10/30/05 (5)
Having looked at a LOT of different fabrics, and measured them, what you have LOOKS good, but I can't be for sure, as the burlap I am familiar with uses jute fiber as the thread material. This has linen fibers for the threads.
However, if you can find some speaker grille cloth that is wider than 48", this could be used with good results as well.
Of course, the expensive fabric alternatives are always there.
If you are interested in ONLY using them as bass traps, and are not as concerned about mid and HF reflections, then just about any cloth will work as a covering for JUST a bass trap, except extremely heavy/thick ones, or ones with an impermeable backing.

Jon Risch
- Re: Jon Risch bass trap fabric choices? - Aaron 01 11:15:32 10/31/05 (0)
  Thanks Jon,
  I did search a bunch of old posts and that is why I was concerned to get the right fabric as I really wanted to do these right. After a day of no luck on the burlap I ordered the Guilford 701 as it was on sale for only $12.25 per yard. Your help has been very valuable and much appreciated.
  Aaron
- Most synthetics will screw up voice sound. - Al Sekela 08:52:30 10/31/05 (3)
  The talk-to-it test is free and quick, and will reveal to even untrained persons that most synthetic fiber fabrics, no matter what their appearance or loft, will modify the sound of voice. This is a large problem if extensive room treatments are to be made with such fabric coverings. The purpose may be to treat the bass only, but the consequence may be to make accurate vocal reproduction difficult.
  - Re: Gosh, even Sonex? nt - geoffkait 13:35:40 10/31/05 (2)
    nope
    - Sonex panels are one of the few synthetics that don't. - Al Sekela 09:26:48 11/02/05 (1)
      Anyone care to compare Sonex with polyurethane foam?
      - Re: Sonex panels are one of the few synthetics that don't. - geoffkait 08:46:56 11/03/05 (0)
        
        In Reply to: Sonex panels are one of the few synthetics that don't. posted by Al Sekela on November 2, 2005 at 09:26:48:
        
        don't bet on it...(it was a trick question.... hehe)
another trick - rhyno 18:11:02 10/29/05 (1)
i also heard / read that you should try to breathe through the fabric; anything that you can breathe comfortably through will do the job.
(i hope this is true, i just build 10 bass panels with the stuff).
$15 / yd seems awfully steep.
rhyno
- Fine for bass only - Jon Risch 19:58:13 10/30/05 (0)
  This method works for material to be used in a bass trap where one is ONLY concerned with it's use in the bass, and not for the mids and highs.
  Materials that can pass one's breath, may still be too dense to avoid reflecting the mids and HF's.
  See my other posts in this thread.
  Jon Risch
Talk to it. - Al Sekela 11:52:08 10/29/05 (2)
The easiest way to test fabric is to speak to it while moving closer to it, and listen to the reflected sound of your voice.
Start with a bare hard surface, such as a wall. Say a word or phrase over and over while you move your head closer to it.
Then hold a folded piece or flattened roll of the fabric over the wall and repeat. Notice the change in timbre and diminished loudness compared to the hard surface.
Compare different fabrics, and choose the one that gives the most neutral sound with diminished reflection. I found a cashmere wool scarf to be the best sample, and am looking for more of this material in inexpensive outlets. Wool blanket material is also good.
I'm serious about this, but the method seems silly. Other people who do not understand what you are doing will think your are crazy if you do this in a fabric store, so be discreet.
- Hard to learn, and only midrange results - Jon Risch 19:55:41 10/30/05 (0)
  First, this is hard to learn to do, and takes more practice than most people are going to be willing to put in to learn it well enough to walk into a store and do it with decent results.
  Second, it will only provide results for the midrange, and not provide much in the way of feedback for HF's.
  For instance, many velours and thick wool materials absorb voices just fine, but reflect virtually ALL the HF's above 5 kHz, with amazingly little loss.
  
  Jon Risch
- I did, now they won't let me into that store anymore. :) - Jack Seaton 14:06:26 10/29/05 (0)
  Good suggestion. You have to remember that the human voice has a frequency spectrum of itself, which is less than full frequency spectrum. The fundemental frequency of the human voice starts around 100 Hz and extends (for some folks) up to 1200Hz. Harmonics will take it much higher, of course, but you might have to bring in a kettle drum to determine the attenuation at sub 100Hz regions. :)
  Then again, what you chose to use behind the fabric will also determine which frequencies are attenuated and at what degree.
  It is fun to try new and different materials and methods to see what works best for you, in your room. It took me a month of Sundays to get it right, but it sure paid off.
  Best,
  Jack
  P.S. My home made room treatment devices work much better than my aftermarket ones did, which I sold and bought more software. :)

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