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Discussion Starter · #1 ·
I've read several sub building threads where fiberglass insulation has been suggested as a damping material for the interior of subs. This could potentially be overly cautious, but I see this as potentially hazardous. Fiberglass insulation should really be restricted to sealed applications (such as in a wall) because the particulates from it are known carcinogens. The glass is essentially bio-chemically inert, but the material becomes a permanent lung irritant.

A ported sub would constantly be breaking off invisible bits of glass strands and blowing them out of the port into a nicely sealed home theater, where the occupants spend hours at a time. When I am in exposure to fiberglass insulation, I wear a full Tyvek suit and a full-face sealed breather. I only see the actual glass dust when the light hits it just right, and it can really fill the air.

End of sermon. Flame at will.:nono:
 

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You do bring up a good point both fiberglass and mineral wool can be dangerous if handled incorrectly. Personally I use the latter rather than the former because it is far cheaper while being equally effective. Whenever I use either in a ported application I carefully wrap it in cloth or batting to lock all fibers in place. This traps all the fibers in place under the material stopping them from being dispersed throughout the room. I also take this same precaution with my room treatments.

Blindly placing these materials within a ported cabinet could be hazardous, but common sense and planning can prevent these issues.
 

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Discussion Starter · #5 ·
Oh, I see. Well, there was a response that claimed that if fiberglass in subs were a problem, then so would it be as home insulation. That is not necessarily so, if there is proper detailing. Fiberglass must be encased, sealed off from the conditioned space. Even in a crawlspace, it is a very good idea to attach a membrane to the underside of the joists. A radiant barrier is good for this, as it has three functions: reflecting radiated heat (especially important in cold climates), containing the glass fibers (important when you have to be down there), and creating an air barrier, which increases the effectiveness of the insulation.

Not that you wanted to know that, but I do go on...

Oh, and there was another response about not ever seeing the fibers. As I mentioned earlier, the stuff is invisible until you catch it in a sunbeam.
 

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Glass fibers remain in the lungs? Glass fibers are smooth, they can pass through the lungs, unlike asbestos which have barbs, like a fish hook, that stay in the lungs.
 

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I have been dealing with insulation for a long time. lol I know a lot of installers, that have installed fiberglass for 30+ years without a nuisance mask, and had no damage from the glass fibers, most have other vices causing the lung damage. I myself deal with the fibers on a daily basis. lol
So I just put my $.02 worth. :bigsmile:
 

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My parents just bought a new home and the fiberglass is unincased in the basement. There are intake vents for the furnace down there as well. If this were a hazardous situation don't you think the building codes would dis-allow it?
 

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My parents just bought a new home and the fiberglass is unincased in the basement. There are intake vents for the furnace down there as well. If this were a hazardous situation don't you think the building codes would dis-allow it?
No . . . . but the rest of my answer is NOT a HOME THEATER SHACK subject and not on subject here.
 

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A quick google found this site.

Some excerpts:

"1999- OSHA and the manufacturers volunta- rily agreed on ways to control workplace exposures to avoid irritation. As a result, OSHA has stated that it does not intend to regulate exposure to fiberglass insulation."

"2000- The National Academy of Sciences (NAS) reported that epidemiological studies of glass fiber manufacturing workers indicate "glass fibers do not appear to increase the risk of respiratory system cancer"."

"2001- The IARC working group revised their previous classification of glass wool being a possible carcinogen. It is currently considered not classifiable as a human carcinogen. Studies done in the past 15 years since the previous report was released, do not provide enough evidence to link this material to any cancer risk."


It would see that the minimal exposure we would experience during a loud passage from a ported subwoofer is much much smaller than the exposures in these studies, and even still they concluded that there was not sufficient evidence of a health hazard.

Additionally a simple silk stocking at the base of the port would catch any escaping fibers if they irritated listeners.
 

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******, Justin, I'm an engineer, not a doctor!

ETA: Crazy. They could say it on TV in the 60's, but it's censored here. Corn shucks.
LOL! I had one of mine censored as well. This will take some getting used to! :heehee:

SheepStar
 

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Just go to Walmart and buy cotton polyfill. All of these materials are so close to each other in effectiveness that its not worth getting worked up over. The cotton polyfill is cheap, doesn't give you a case of the scratchies and is easily available. What isn't to like?
 

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Just go to Walmart and buy cotton polyfill. All of these materials are so close to each other in effectiveness that its not worth getting worked up over. The cotton polyfill is cheap, doesn't give you a case of the scratchies and is easily available. What isn't to like?
Polyfill is not even comparable in effectiveness to OC705 or 8lb mineral board in terms of dampening capabilities. I am not sure your source on such a statement, but it just isn't so. This is similar to those who think egg crate foam has similar dampening properties as OC705 or 8lb mineral board while actual testing on the materials shows otherwise.
 

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Well.... I'm talking about fill inside the box, not room treatments. There is no reason for 6lb. density fiberglass inside the box. I've used 3lb density behind midrange drivers before but with inconclusive results.

Lets lay out the two functions for the fill.

#1. Increasing effective enclosure size. I'll stand by my statement.... I've never measured a big difference in performance among materials. The differences are only minor and swamped by other issues.

#2. Trying to damp enclosure resonant nodes. This is an area where different density materials may be more or less effective. It depends on the resonance though. The size of standard subwoofer boxes doesn't lend itself to having meaningful resonant issues down low in frequency. The box just isn't physically large enough to set up those kind of standing waves at those frequencies. The different density of materials make them more/less effective at different bandwidths and I'm having a hard time seeing an application using OC705 where its useful inside the enclosure. It will just eat up volume.
 

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Well.... I'm talking about fill inside the box, not room treatments. There is no reason for 6lb. density fiberglass inside the box. I've used 3lb density behind midrange drivers before but with inconclusive results.
I realize that and my comments are regarding cabinet internals, but the location of the wave does not change the amount/type of dampening required to minimize/remove it.

#1. Increasing effective enclosure size. I'll stand by my statement.... I've never measured a big difference in performance among materials. The differences are only minor and swamped by other issues.
It is possible to increase effective cabinet size with certain types of material, but this is a fairly ineffective method compared to making a larger cabinet.

#2. Trying to damp enclosure resonant nodes. This is an area where different density materials may be more or less effective. It depends on the resonance though. The size of standard subwoofer boxes doesn't lend itself to having meaningful resonant issues down low in frequency. The box just isn't physically large enough to set up those kind of standing waves at those frequencies. The different density of materials make them more/less effective at different bandwidths and I'm having a hard time seeing an application using OC705 where its useful inside the enclosure. It will just eat up volume.
Dampening material is needed when the cabinet size is larger than 1/4 the size of the frequencies being reproduced. While it is true that most subwoofers aren't large enough for this to matter many Sonotubes do fall in this category and are poorly dampened.

As far as usage in a midrange or something this is where standing waves become a larger issue and where I generally recommend stuffing a cabinet full of a high grade dampening material such as OC705 or 8lb mineral board - a cabinet such as this should be an anechoic chamber in the passband. In regards to such materials eating up volume that just isn't true the largest issue that will occur is increased low frequency roll off which can be adjusted with varying amounts of dampening material or proper subwoofer integration.
 

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Ok... so we can agree to disagree. :)

I stuff subs mainly to increase the effective size and get some minimal out of band attenuation. I'm not at all sure the attenuation is audible in the vast majority of situations. The spurious noise is typically below the -45dB down point and masked by program material. If you are getting noise from the enclosure that is greater than the the noise floor of the driver/port/amp then its worth building a better enclosure.
 

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Polyfill is not even comparable in effectiveness to OC705 or 8lb mineral board in terms of dampening capabilities. I am not sure your source on such a statement, but it just isn't so. This is similar to those who think egg crate foam has similar dampening properties as OC705 or 8lb mineral board while actual testing on the materials shows otherwise.
Hey Andrew, how does r-13 stack up against these?
 

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Ok... so we can agree to disagree. :)

I stuff subs mainly to increase the effective size and get some minimal out of band attenuation. I'm not at all sure the attenuation is audible in the vast majority of situations. The spurious noise is typically below the -45dB down point and masked by program material. If you are getting noise from the enclosure that is greater than the the noise floor of the driver/port/amp then its worth building a better enclosure.
I have already alluded to the fact that many subs do not need dampening to remove wave created resonance due to their size in relation to the created wavelength size, but when it comes to other frequencies as outlined previously it is of extreme importance. Do note that depending on various other aspects of design use of proper dampening might not create audible differences (i.e., there are far weaker links in the chain).

Hey Andrew, how does r-13 stack up against these?
125hz 250hz 500hz 1khz 2khz 4000hz NRC
R-13 3.5" 0.95 1.30 1.19 1.08 1.02 1.00 1.15
OC705 2.0" 0.16 0.71 1.02 1.01 0.99 0.99 0.95

It would seem the OC705 (mineral wool acts very similarly) would be more efficient considering the R-13 is one and a half times as thick. OC705 is unfaced, wall mounted.

Taken from a great site for comparing various materials absorption coefficients.
 
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