Do any of you worry about fiberglass insulation in ported subs? - AVS Forum
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post #1 of 10 Old 03-25-2013, 05:44 PM - Thread Starter
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Insulating my attic hatch last week reminded me of the danger of breathing in fiberglass fibers. The Owens Corning packaging notes that inhaled fiberglass is a potential lung cancer hazard. It's at the very least a skin irritant for sure.

Looking for a subwoofer, and some are reportedly insulated with fiberglass. Seems that there's a tradeoff between safety and loud, deep bass.

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post #2 of 10 Old 03-25-2013, 06:24 PM
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Originally Posted by PoseidonXXL View Post

Looking for a subwoofer, and some are reportedly insulated with fiberglass. Seems that there's a tradeoff between safety and loud, deep bass.
Home insulation fiberglass should not be used in speakers. The correct material is rigid Owens Corning Type 700 fiberglass boards, which doesn't pose an environmental problem. But you're mistaken about its usage, which is to damp internal reflections of midbass and higher harmonics. It has nothing to do with how low or loud a sub will go.

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post #3 of 10 Old 03-25-2013, 07:19 PM - Thread Starter
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I was referring to the use of fiberglass in a ported sub, Bill. In a sealed sub, nothing inside the sub's going to be ejected through the port(s).

I don't see any subwoofer manufacturers using fiberglass board. Do you? The pics I've seen suggest the use of batting, not board.

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post #4 of 10 Old 03-25-2013, 08:38 PM
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Originally Posted by PoseidonXXL View Post

I was referring to the use of fiberglass in a ported sub, Bill.
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I don't see any subwoofer manufacturers using fiberglass board. Do you? The pics I've seen suggest the use of batting, not board.
I couldn't say who uses what, only what they should be using. Type 700 comes in many thicknesses, it's typically used as insulation but it's also coated with aluminum foil for use as heating ducts and plastic faced for use as lightweight drop-in ceiling tiles. It's usually yellow color. It has one of the highest coefficients of sound resistivity, so it's excellent for cabinet lining and room sound treatment panels.

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post #5 of 10 Old 03-26-2013, 10:05 AM
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They almost always use Polyfill or something similar which is 100% Polyester, it's not fiberglass.
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post #6 of 10 Old 03-26-2013, 01:13 PM
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Never thought twice about it. My ported DIY subs use good old pink R-19, but I've never noticed any fibers floating around the room or building up on furniture in a dedicated theater room.

From the photos I've seen, I'm pretty sure SVS uses batt insulation for stuffing/lining. I would expect most other mfgs do, too. Dickason's testing in the LDC showed fiberglass insulation to be as good or better than other options, including some of the supposedly purpose made products. On a bulk mfg basis, I imagine it's also much more cost effective.

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post #7 of 10 Old 03-26-2013, 01:55 PM
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Originally Posted by riverwolf View Post

Dickason's testing in the LDC showed fiberglass insulation to be as good or better than other options,
I haven't looked at Vance's book since the first edition, but I think you'd find that if he mentions fiberglass it's Type 700, and chances are he used the test results of one of our colleagues at Speaker Builder and AudioXpress magazines, Gerry Koonce, who did a major test a dozen or so years ago. He also recommends not using insulation glass. Environmental issues aside, it also can get into the driver motors, acting as an abrasive, leading to driver failure.

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post #8 of 10 Old 03-26-2013, 03:32 PM
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OC 700 series fiberglass is used rarely in speakers, or only for specific applications. Remember that most modern fiberglass you purchase in a store is and has been formaldehyde free for some time now. The fibers are an irritant if they are stirred up, but that does take some significant port air flow (subwoofer range, less likely with speakers). For some custom projects I have stapled in the fiberglass batting with a very open mesh like a spandex or similar to keep everything in place with huge port airflow.

The most "green" of the available materials is recycled cotton insulation. Some sell it as acoustic cotton, with the brand name of Bonded Logic now available at or through many home improvement stores such as Menards and Lowes. The main hurdle is cutting it, as the fibers don't cut easily with a razor.

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post #9 of 10 Old 03-26-2013, 04:15 PM
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Originally Posted by Bill Fitzmaurice View Post

I haven't looked at Vance's book since the first edition, but I think you'd find that if he mentions fiberglass it's Type 700, and chances are he used the test results of one of our colleagues at Speaker Builder and AudioXpress magazines, Gerry Koonce, who did a major test a dozen or so years ago. He also recommends not using insulation glass. Environmental issues aside, it also can get into the driver motors, acting as an abrasive, leading to driver failure.

Bill, over the years you continually come across as a bit of a curmudgeon towards the usage of stuffing/fill materials.

Since I have it relatively handy, I pulled my 4th edition LDC off of the shelf. Vance clearly states he is referring to standard R19 fiberglass insulation. Further, the text doesn't suggest in any way to me that he didn't perform the comparison measurements himself. The extensive reference section at the end of the chapter includes a couple of stuffing/fill articles, but none were authored by Koonce.
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post #10 of 10 Old 03-26-2013, 04:35 PM
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Originally Posted by riverwolf View Post

Bill, over the years you continually come across as a bit of a curmudgeon towards the usage of stuffing/fill materials.

Since I have it relatively handy, I pulled my 4th edition LDC off of the shelf. Vance clearly states he is referring to standard R19 fiberglass insulation. Further, the text doesn't suggest in any way to me that he didn't perform the comparison measurements himself. The extensive reference section at the end of the chapter includes a couple of stuffing/fill articles, but none were authored by Koonce.
Like I said, I haven't looked at Vance's book since the first edition. I've seen how R19 falls apart, so I won't use it or recommend it.

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