Question about box polyfill stuffing

I am building a sealed box for my Perfect 12 sub. I am going to line the inside with polyfill, but don't know the effects of stuffing the whole box loosely with the material, lining the sides only, etc. What are the acoustic affects of the different methods of dampening the inside of the box?

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2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12

Two reasons to use polyfill. First, it keeps waves coming off the rear of the sub from bouncing off the back of the box and effecting the woofer. Second, it allows the woofer to "see" a bigger box. I usually like to line the sides and rear with about two inches of material. You will find varied opinions on this, for instance, most JL factory boxes are lined right up to the rear of the woofer. Their method seems to make the woofer sound a little better in exchange for some effiency.

Lining your box will give you more sound but doesn't dampen the crap sound as much as filling your whole box. However filling your whole box the polyfill cuts down alot on the noise but it also cuts down on the over all volume; killing your subs efficiancy causing you to push your subs more causing them to work harder and shorten their life span which is then accelerated by the insulation storing the heat and causing your subs to overheat and DIE!

But you can't beat the sound of a properly filled box.

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Tell the Snap-On guy I'm not here!

I would stay away from stuffing the box all together. I just recently built a Box for my 10's and I sprayed all the inner walls with a rubbereized undercoating. I worked very well to keep the resonation down inside the boxe and also helped a bit with air tightness. BTW, the box sounds really good.

Chris

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Alpine CDA-9833 HU
Diamond Audio M661 Components
MTX Thunder T6.6 Components:rear fill:
Cadence Q400 4 Channel Mains + rears
Thunder 801D Subs
MTX 1004 10's
Dual 4g wire to rear
4g grounds

Thanks for the suggestions, I will not fill the entire box. If I did decide to use polyfill around the sides, would I just use 2 inch sheets secured to the inside? And I am assuming the front baffle is not lined?

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2004 BMW 325ci.
Alpine CDA-9885
JL 300/4 and 250/1
JL XR 5.25 comps
Infinity Kappa Perfect 12

I think polyfill is more effective if you stuff the box instead of lining the walls. The general I think I've heard is 1 pound per cubic foot about. And don't stuff it too much or it will defeat the gain of stuffing your box. It's just something you have to play around with a little bit.

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From my experiance (which is limited and riddled with idiotic mistakes) Every box reacts differently. Experiment with it.

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Nik
Jeeputer Progress
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Check it out.

are there any substituse for polyfil?

any fabric store polyfil is fine. Stay away from Parts express Acustastuff though! SQ boxes use 2-3" lining of polyfil about 1lb per cubic ft and spl boxes should use Deflex Pads on the backside of your enclosure.

The best I've used is the quilt stuffing the little old ladies use. It works great and it's a ton cheaper then anything my suppliers sell.

69burbn: why do you say stay away from AcoustaStuff? I've always had success with it.

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New Project: 2003 Pathfinder

Whats the difference from the acustastuf and polyfil?

Acoustastuf is a more consistent fiber diameter, and as it is drawn, it is crimped, with very even crimp spacing. This makes Acoustastuf FAR more predictable than the polyfil you go to Walmart and buy for a buck for a 4 cubic foot bag. Yes, it IS more expensive, but I think the recommendation to avoid Acoustastuf is only one person's view, because that person MIGHT not know what he is doing when stuffing an enclosure. If it were such a bad product, then every high-end speaker manufacturer in the world wouldn't be using it in their 20, 30, 40 thousand dollar enclosures... The Acoustastuf IS a good product, one that I recommend (again with every other audio professional in the world - that or long fiber wool) VERY highly...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."

haemphyst how do you stuff the enclosure? im lookin into this stuff so i can stuff my boxes (3 cubic feet each) and how woudl i go bout doing it?

The recommended start point is .5 pounds per cubic foot. Generally, I just kinda fluff it up, and send it into the enclosure by the handfull. Make certain you stuff evenly, try not to have a whole bunch of big lumps of the stuff in one or two places... Because the fibers are very long, and relatively coarse, they can be right up to the back of the woofer, no problem there, but you do need to make certain it stays away from the port opening, if you are using a vented enclosure. If you have a 4 inch vent, you must keep it, at a minimum, two inches from the port opening. A 3 in port requires 1.5 inches, etc., etc...

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It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."