Acoustic stuffing differences , any ideas ?

bob s

Active Member
I have dismantled some loudspeakers that had badly damaged boxes. I saved the stuffing material for future use. The material out of the AR-14's is coarser in texture. The material from the Infinity's is a much finer in texture, almost silly feeling. I am wondering which would be superior for stuffing some bookshelf speakers, like my Optimus LX-5's, or if it matters. Some folks swear that plain old fiberglass is the best, but it is so dogone itchy, I want to stay away from it if possible. Any thoughts ?

Bob S
 
The move away from fiberglass was for the reason you just said. Day in and day out was a discomfort for the speaker makers. It was the most common at the time.
And of course the material used has a big effect on the sound as you said. For your limited use with gloves it may be a good option.
Good luck.
 
Fiberglass still reigns supreme, but Parts Express has AcostaStuff. I've had very mixed results from polyester pillow stuffing.
GeeDeeEmm
 
Infinity's been using the polyester-looking stuff since at least the 1980s, for whatever that's worth.
 
So the parts express acousta stuff is different than polyfill? I think that is what was in the Infinities, its real soft and silky feeling. I suppose I clubs stuff one speaker with one material and one with the other and see if I can discern the difference.
 
I have dismantled some loudspeakers that had badly damaged boxes. I saved the stuffing material for future use. The material out of the AR-14's is coarser in texture. The material from the Infinity's is a much finer in texture, almost silly feeling. I am wondering which would be superior for stuffing some bookshelf speakers, like my Optimus LX-5's, or if it matters. Some folks swear that plain old fiberglass is the best, but it is so dogone itchy, I want to stay away from it if possible. Any thoughts ?

Bob S

This should answer your question.
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I read the linked article, still not sure if I totally understand the concepts, but I'm no engineer so can't argue the point. Without sophisticated test equipment it would be hard to really pick apart any small changes the various materials make. I guess I'll just stuff em and see what happens.
 
I have dismantled some loudspeakers that had badly damaged boxes. I saved the stuffing material for future use. The material out of the AR-14's is coarser in texture. The material from the Infinity's is a much finer in texture, almost silly feeling. I am wondering which would be superior for stuffing some bookshelf speakers, like my Optimus LX-5's, or if it matters. Some folks swear that plain old fiberglass is the best, but it is so dogone itchy, I want to stay away from it if possible. Any thoughts ?

Bob S
You can get bags of polyfill (polyester filler) pretty cheap ($7-10 bag) at places like Michaels. Its used for creating/stuffing pillows and such and is a readily available and safe media. I had heard some car audio folks stuff their cabinets with it.
Yellow building insulation fiberglass is real nasty stuff and recommend NOT putting it in ported speaker boxes where broken bits of the fibers can be expelled when bass is played. YUCK!

I have been modding a pair of Heathlkit Valencia type speakers recently. The cabinets have sheets of, I presume, Rock wool stapled to the sides and back of the cabinet. I installed a sheet of stiff fiberglass between the bass area and the horn area. An audio guru I am working with gave me a large box of raw lambs wool, with details on pulling the fibers apart for the most expanded use as stuffing inside. Its got a nice feel (lanolin in the fibers) smells pleasant, and the (ported) boxes have a nice bass response now. The little flecks of white are some polyfill media I had tried before.
This shows maybe 6-8 ounces of lambswool really pulled apart and fluffed up in air.
There is a 15 inch woofer underneath.

You can buy it lambs wool on ebay (cheap!) - https://www.ebay.com/bhp/raw-wool


Woofer-lamb-fluffed_6563.jpg woofer-Area-B4_6561.jpg Woofer-screened_6562.jpg

This is a picture from one of the ebay ads - looks just like what I have at home,
before I pulled all the strands apart and fluffed it up!

eBay-lambswool-l1600.jpg
 
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I've heard many use Rock Wool which is also a fiberglass.

We've discussed Rockwool before, and my personal opinion (ie, likely worthless) is that while it does function as intended as a sound barrier/insulator for home use, it's not good for the qualities that are generally sought by speaker builders. This is because Rockwool (compared to fiberglass) is very dense and minimally air permeable - ie, air movement thru it highly restricted. I think it would be impossible, for example, to use Rockwool in a transmission line the same way as fiberglass or Fiberfill simply because it will not allow air waves to move throughout the enclosure unimpeded.

Additionally, it weighs 2.5 lbs per square foot! ("ROCKWOOL insulation is a rock-based mineral fiber insulation comprised of Basalt rock and Recycled Slag.") That means that, whereas fiberglass will actually "fool" (for lack of a better term :dunno:) the woofer into seeing a larger (sealed) enclosure volume as it is added to the box, Rockwool will instead occupy space and thereby decrease enclosure volume.

https://cdn01.rockwool.com/siteasse...fing-Insulation-Techdata.pdf?f=20180419081800

JMO, you understand. ;)

GeeDeeEmm
 
I worked 35 years in a power plant where they used rock wool as high temperature insulation. It's really nasty stuff, very irritating, so I'll stick with the fiberfill and similar materials. Lambs wool sounds interesting, and we have friends that have sheep ( same critter I suppose ) Maybe we can talk them out of a few handfuls come shearing time.
 
Lambs wool sounds interesting, and we have friends that have sheep ( same critter I suppose ) Maybe we can talk them out of a few handfuls come shearing time.

You likely don't want to do that. Raw sheep wool is covered in lanolin (grease), is filthy, and it stinks. This is why all those jokes about sex with sheep are somewhat misplaced. As an Aussie I knew a long, long time ago once said to someone making jokes about sex with sheep, "You ever smell a sheep, mate?" Anyway, it will be a dense, greasy, dirt mass.

The speakers with wool stuffing use the cleaned and carded variety, with long fibers, which fluffs up a lot better. I believe it was Bailey who first introduced this for transmission-line stuffing. You'll see this called "long fiber" which means the fibers are (IIRC) about six inches long. Much of the wool sold as batting or padding is shorter fibers twisted together which doesn't matter for upholstery, but it does matter for speakers.
 
I have dismantled some loudspeakers that had badly damaged boxes. I saved the stuffing material for future use. The material out of the AR-14's is coarser in texture. The material from the Infinity's is a much finer in texture, almost silly feeling. I am wondering which would be superior for stuffing some bookshelf speakers, like my Optimus LX-5's, or if it matters. Some folks swear that plain old fiberglass is the best, but it is so dogone itchy, I want to stay away from it if possible. Any thoughts ?

Bob S
At the end of the day I would just use Acousta-Stuf but it doesn't hurt to bag up the fill you mentioned for other uses. The advantage of Acousta-Stuf is that will resist settling over time. There is a need to keep the filaments spread in the material to work as intended in providing resistance to the air flow.

Fiberglass is better for lining cabinet walls to target the high pressure areas that build up against the interior walls. I don't have a big concern for the loose fibers but the cautions above are well founded. Rockwool is best used for acoustic absorption for treating walls/ceilings or in acoustic panels. I certainly wouldn't go there for speaker cabinet uses.
 
Well believe or not used some memory foam used for bed I had laying around and it work great for my DIY speakers.
 
Good point about the raw lambs wool, ick.....acoustastuff or equivalent will likely work fine. I have seen folks use the eggcrate foam to line enclosure walls, then stuff the insides with other fibers. The foam they make mattresses is probably too dense and would act to reduce the interior volume of the enclosure, just the opposite of the intention.
 
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