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Speaker cabinet insulation

AudioGMan

AudioGMan

Well-Known Member
Does anyone know what type of insulation was used in some vintage speakers that have yellow insulation applied to the interior cabinet walls? Is it fiberglass? Don’t fiberglass particles make their way out of a port when air is rushing out of the port? I just bought a pair of American Acoustics D8500 speakers. I removed a woofer to inspect the internals and there is zero insulation in there. I want to add some type of damping and was wondering if stapling pink fiberglass batting to the inside walls would be fine to use. I’m sure adding some insulation will improve the sound. Any input is welcomed.
 
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Some times rock wool was used. It looks similar to yellow fiberglass though slightly different in some physical and acoustic properties. There are other options now, some made for this purpose, some adapted to it.
I think that fiberglass is so intertwined there would be little chance of fibers blowing out through the vent though none of the vented speakers I have left used fiberglass.
 
AudioGMan said:
Don’t fiberglass particles make their way out of a port when air is rushing out of the port?
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Air doesn't rush out of the port as such, it moves in and out. Think of it as AC rather than DC air "current". The port will suck in as much as it blows out, but I suppose some migration of particles is inevitable.
I have a ported cabinet with rockwool inside and I'm not particularly bothered by thought of particles coming out, but it might make sense to use something like the stuff in the post above if you're more cautious.
 
rothwellaudio said:
Air doesn't rush out of the port as such, it moves in and out. Think of it as AC rather than DC air "current". The port will suck in as much as it blows out, but I suppose some migration of particles is inevitable.
I have a ported cabinet with rockwool inside and I'm not particularly bothered by thought of particles coming out, but it might make sense to use something like the stuff in the post above if you're more cautious.
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Thank you for the input. I understand that the air is moving in/out of the port but sometimes I’ve listened at loud enough levels with heavy bass material that I can feel the air from my listening position that is 12’ away.
 
AudioGMan said:
Thank you for the input. I understand that the air is moving in/out of the port but sometimes I’ve listened at loud enough levels with heavy bass material that I can feel the air from my listening position that is 12’ away.
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:rflmao:
 
we421a said:
https://www.parts-express.com/Acousta-Stuf-Polyfill-1-lb.-Bag-260-317

I have used these for diy cabinets and it works well in my vintage Jensen cabinets as well
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we421a said:
https://www.parts-express.com/Acousta-Stuf-Polyfill-1-lb.-Bag-260-317

I have used these for diy cabinets and it works well in my vintage Jensen cabinets as well
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Thanks for the recommendation. Can it be applied to the inside walls or is that meant for just stuffing a sealed enclosure? My speakers are ported.
 
AudioGMan said:
Thank you for the input. I understand that the air is moving in/out of the port but sometimes I’ve listened at loud enough levels with heavy bass material that I can feel the air from my listening position that is 12’ away.
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Unless something is extremely wrong with your speaker, then more air can't come out of the port than goes in. It's not unusual to feel bass impulses coming from the speaker, and that's indeed air moving, but it's not like the port is gushing out a stream of air like there's an air compressor in there. The air in the port is just + and - pulses.

FWIW, I built a pair of ported speakers a couple of years ago and l lined them with fiberglass. In another thread where somebody was concerned with a stream of fiberglass particles shooting from the ports, I did an experiment. I placed a small amount of fiber in the port a couple of inches in and cranked it up on some bass heavy music. The fibers wiggled in the port, but never made any forward progress. These speakers have the ports tuned to 28Hz and reproduce bass with some authority, tri-amped with an amp driving each woofer. They "move some air", but none streaming from the ports.

That said, the stuff I used was 1" thick Wrap-On 16550 insulation and it's no longer made. It's non-shedding fiberglass insulation and is very similar to what JBL used in ported speakers for years and years.
 
Jeffery said:
Unless something is extremely wrong with your speaker, then more air can't come out of the port than goes in. It's not unusual to feel bass impulses coming from the speaker, and that's indeed air moving, but it's not like the port is gushing out a stream of air like there's an air compressor in there. The air in the port is just + and - pulses.

FWIW, I built a pair of ported speakers a couple of years ago and l lined them with fiberglass. In another thread where somebody was concerned with a stream of fiberglass particles shooting from the ports, I did an experiment. I placed a small amount of fiber in the port a couple of inches in and cranked it up on some bass heavy music. The fibers wiggled in the port, but never made any forward progress. These speakers have the ports tuned to 28Hz and reproduce bass with some authority, tri-amped with an amp driving each woofer. They "move some air", but none streaming from the ports.

That said, the stuff I used was 1" thick Wrap-On 16550 insulation and it's no longer made. It's non-shedding fiberglass insulation and is very similar to what JBL used in ported speakers for years and years.
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I didn’t mean that I can feel a continuous flow of air. But on occasion I can feel a blast of air from the port. I’ve owned several pairs of speakers that house 15” woofers and even some 12” with the same experience. Nothing wrong with any of the speakers.
 
AudioGMan said:
I didn’t mean that I can feel a continuous flow of air. But on occasion I can feel a blast of air from the port. I’ve owned several pairs of speakers that house 15” woofers and even some 12” with the same experience. Nothing wrong with any of the speakers.
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Mine do as well when I am way up in the volume levels. If you just want to add some mass and make them dead, I add some layers of rubber Ice shield to my cabinets which you can buy smaller rolls of.
 
If you're worried about fiberglass you can always hit it lightly with Krylon Fixatif. I've heard of using hairspray too but the fixatif is acid free.
 
NH-MAN said:
If you just want to add some mass and make them dead, I add some layers of rubber...
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I'm not sure what the OP's intention is, but lining vented cabs with something absorbant is usually done to reduce mid frequency reflections inside the cabinets which can colour the sound. However, in this case the woofer is crossed over to a sealed mid range driver at 400Hz, so I doubt the addition of some rockwool (or similar) would be of much benefit at all.
https://worldradiohistory.com/hd2/I.../HiFi-Stereo-Review-1986-06-OCR-Page-0042.pdf
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AudioGMan said:
Thanks for the recommendation. Can it be applied to the inside walls or is that meant for just stuffing a sealed enclosure? My speakers are ported.
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I use inside of the wall. You can adjust the thickness to your liking then apply tape over it
 
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