what happens when you put polyfill in a ported enclosure?

[supmet]

From http://www.klausaudio.com/subwoofer-...woofer-box.php

In general, a subwoofer box that would require polyfill would be a subwoofer box that is close to, or smaller than the manufacturer's minimum recommendations for internal volume. Polyfill will make a subwoofer perform as if it were in a larger enclosure by slowing sound waves as they pass through the polyfill. The physical internal volume of the subwoofer box remains the same, yet the effective internal volume changes when polyfill is added.

Sealed subwoofer boxes are the best candidates for polyfill. It is possible to use polyfill in a ported enclosure, but this is not recommended, as it would then change the tuning of the box. Sealed subwoofer boxes generally yield a better, flatter frequency response curve when the enclosure is larger (to a certain point). If you need a subwoofer box of a given size, and your available trunk dimensions do not allow you to customize a subwoofer box with enough internal volume, it is possible to get the subwoofer enclosure built a little smaller than desired and have polyfill added. This will make the subwoofer box "appear" larger to the subwoofer.

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Interesting. I just cut my box down a little because it was taking up too much room, but it definitely lost some of its punch. I'm gonna go to a craft store and try this out :D