Hi, I have built a subwoofer box for my 2-12" Clarions. It's a sealed box with a divider in the middle with 1.25 cu.ft. airspace in each chamber. The manufacturer recommended 1.50 cu.ft. unfilled and 1.25 cu.ft. filled. My question is since my box has 1.25 cu.ft of air space, how much polyfil do I need to put in each speaker chamber? Any help would be appreciated.

Thanks, Mariano

I'd probably put about 1 pound of polyfill per chamber for that box.

Here is Tom Nousaine's test of fiberfill from the old Car Stereo Review mag:

http://web.archive.org/web/200208082...ces/fiberfill/

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based on tom's findings, which i have been using for years and find very accurate, you need about 21% more volume, so use .75lbs per cubic feet or 1.875 lbs total. This will yield a virtual box size of 3.02 cubic feet total.

Thanks for the info!

i wouldn't even bother will the fill....especially in a woofer box. i think i just muffles the sound. but that's only my opinion.

This audio guru here in Calgary told me something really intesting the other day. He said that by using fibreglass fill, that fiberglass actually cuts up the motor structure of the woofer, thus wearing it out faster, really cool stuff.

polyfill is much better and safer to put in ported boxes.

[ April 12, 2005, 11:02 AM: Message edited by: veeman ]

So how much polyfill would it take to make a 0.7 cuft sealed box 'seem' like a 1.0 cuft sealed box?

I think according to Tom's excellent article that the most you can add is about 1.5 lbs per ft. So if I added 1 lb to a 0.7 cuft box what would the effective size of the box become?


Where is a good place to buy polyfill?

1.75 lbs for a sealed box like yours would yield approx. 36% more virtual volume...therefore about .95 cubic feet. Based on his experiment, 1 lb would give you about 23-25% gain...so about .85-.88 ft^3. Again these are based on his results which seem to be quite accurate at least for me currently, and in the past.