I'm curious what everyones take was on Acousta Stuf or similar products. I remember about 10-15 years ago in my car audio days buying a similar product from Crutchfield for my car sub box. Basically the product claimed that you would achieve deeper bass from your box because the stuffing would atrifically make your sub perform as if it were in a bigger box (like the stuffing gave you additional artifical internal volume).

Anyway in the Parts Express catalog that I received the other day I noticed the product Acousta Stuf that reminded me of the product from Crutchfield I bought years ago. Here's a link to Acousta Stuf:

http://www.partsexpress.com/pe/pshowdetl.cfm?&Partnumber=260-317&CFID=6910941&CFTOKEN=63468264

Just curious what everyones opinion was on such products. I would assume that they are mostly gimmick rather than result-delivering, but from a physics standpoint can anyone chime in as to whether or not they would do any good? I do recall removing speakers from factory enclosures (subs, tower speakers, etc) over the years and seen stuffing in the cabinets, so some manufacturers must feel that it is beneficial in some way.

What does everyone think?

I should also add that I don't recall years ago in my car application whether or not the stuffing made any difference. I guess the only real way to test it is with a SPL meter.

The stuff is polyfill.

Polyfill slows down air movement within the enclosure which makes the enclosure "act" a bit larger.

So from your experience it does deepen bass a tad? Has anyone actually tested with a meter to see what kind of results are achieved?

No one has done a before and after with polyfill? Come on...

So from your experience it does deepen bass a tad? Has anyone actually tested with a meter to see what kind of results are achieved?
I used some in the car sub that I put together....but did not test with and without it.

I prefer results using AcoustaStuf over regular polyfill. I fill sealed enclosures with between 1/2 to 1 lb per cu ft; in ported enclocures I glue wads of it as lining onto the walls. The difference in sound, of course, may be my imagination as my ears aren't as keen as they (maybe) used to be, but working with it is much better. It fluffs out more readily, doesn't seem to want to compact itself and get tangled up. I envision that behavior within the enclosure as the fibers expand and redirect/slow down the back waves.

And yes, that slowing down of the waves will enable a box to appear somewhat larger. Unibox has programming capability if you intend to stuff the enclosure or line the walls.

In general terms, a larger enclosure will yield deeper bass extension...so you could probably say, as a rule, that AcoustaStuf yields deeper bass.

Seems to me, that alot of speaker companies use this type of material to absorb and deaden waves on the inside of speakers/subs.. :)

Warp

Isn't there a point though when you wouldn't want the sub to see any additional box volume? At what point do you go from big to "too big?" I mean take an SVS dual 12" driver box... they have a good amount of internal volume. How do you know if the box performing as if it were bigger (with Acousta Stuf) would actually help?

Here's a short article that Tom Nousaine did on stuffing speakers - link (http://www.moodym.com/audio/fiber.html). There's a longer one with the physics behind it but I'm having difficulty finding it.

-Robert

Here's a short article that Tom Nousaine did on stuffing speakers - link (http://www.moodym.com/audio/fiber.html). There's a longer one with the physics behind it but I'm having difficulty finding it.

-Robert

Very interesting link

That's a cool link...

So basically the stuffing would be good for an application where ahead of time you have determined that you cannot (or will not) provide enough internal volume for your driver(s) of choice so you use the stuffing to allow the sub to "see" more volume...

HOWEVER, if your box is already properly built to spec for optimum driver performance, adding the stuffing perhaps won't do any good?

Stuffing is good for only a few percent gain in apparent box volume maybe 5-10% tops, but that's probably high.

It also helps absorb internal reflections which can eminate eventually and muddy the sound. This is what I believe the primary benefit of box fill is. I generally use egg crate foam in my boxes, cleaner and easier to work with plus the density is more consistent than damping wool.

Box volume dictates driver frequency and transient response. Large box = low bass but not tight, this is an underdamped enclosure. Oppositely a smaller box yields tighter bass at a higher frequency, this is a critically damped box.

Try Vance Dickason's Loudspeaker Design Cookbook (I think it's up to 5th revision now). It is an excellent resource for anyone wanting to understand speaker design, and its really easy to read and understand.