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

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?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.

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

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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.