John Sayers' Recording Studio Design Forum

Hello, this is my first post here, but I have been doing quite a bit of reading.
My question is simple, but I cannot find the answer. From my reading, it doesn't seem that the bass traps everyone is talking about and building here can really absorb the bass frequencies. It was my impression that you would need a terribly thick amount of oc-705 or the like to absorb these lows, and that really a different type of trap was needed - specifically a panel absorber. But, everyone talks about building 'bass traps' of fiberglass wrapped in breathable fabric, and as long as its 4" thick, it'll do the job. Is this true? What is the absorbance coefficient at these extreme lows (below 125 hz) and just how far down in the frequency spectrum is it important to have a flat response? (I have a pair of yamaha hs-50m monitors with no sub).

Thank you. I'm sure I will have many more questions to come.

A few more questions I couldn't find an answer to:

I am moderately worried about the health issues of fiberglass. I am not paranoid. I just want the best reasonable protection. I read wrapping in plastic is a bad idea b/c mold could result. Do you think burlap is enough or is there something more I can do to make it even safer (binding glue of some sort)?

Also, according to http://www.bobgolds.com/AbsorptionCoefficients.htm, Rockwool seems to be a better absorber than OC-703/705. Also, its water and fireproof. But, I guess, it crumbles a bit? Ultimately, wouldn't rockwool be better?

"I am moderately worried about the health issues of fiberglass. I am not paranoid. I just want the best reasonable protection. I read wrapping in plastic is a bad idea b/c mold could result. Do you think burlap is enough or is there something more I can do to make it even safer (binding glue of some sort)?"

The best reasonable protection is a facial type dust mask and a long sleeved shirt. No worries:) If you inhale the stuff for say twenty years or so it's gonna be a problem, but so would inhaling say, cigarette smoke.

In general, you may run the risk( Re:wrapping in plastic) of making a dual vapor barrier, depending on how you do this type of thing. In general, I don't think I have ever read of anyone wrapping insulation in plastic. But I am aware that you can purchase it this way. For your application, I would not get plastic wrapped insulation.

You don't want to get burlap either. The ability for burlap to catch fire and spead is well documented. No glues or binding either, it defeats the ability of the insulation to function.

Hope this helps,

Brien

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Brien Holcombe
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Sound: You can't stop it, you can only try to contain it.

Very much. Thanks. But every do-it-yourself on here mentioned burlap if any fabric at all, so I do not know of any alternative (other than generically, it should be breathable). What fabric would you recommend? Price and appearance are both a factor for me, but most importantly, how well it holds the fiberglass particles inside.

And please tell me, if it is just as easy to obtain and price is disregarded, is rockwool or fiberglass (i.e. oc-703) preferable?

some links which with answers you need:
viewtopic.php?f=3&t=12459
viewtopic.php?f=2&t=1742

Ok, I found this http://www.avsforum.com/avs-vb/showthread.php?t=1123719 on dye sublimation and I just have to know where you can go to get this done. Also, can they print anything you want on the fabric? What fabric would be ideal for this? And how much does it cost?

Also, another question

The Master Handbook of Acoustics says:

Sound is reflected from objects that are large compared to the
wavelength of the impinging sound. This book would be a good
reflector for 10 kHz sound (wavelength about an inch). At the low end
of the audible spectrum, 20 Hz sound (wavelength about 56 ft) would
sweep past the book and the person holding it as though they did not
exist, and without appreciable shadows.

I assume this is referring to thickness when it is saying large? The reason I ask is I keep reading that you can use like an FRK cover or plastic painter's drop cloths over the bass trap to allow reflections at higher frequencies to keep the room live. But, isn't this thickness inconsequential?

Thanks again.

Glenn is a regular on this forum so let's see if he's in town

GLENN, tell us more about the "painted" absorbers, I am (or rather the misses is) interested too!