What is your take on polyfill?In your opinion,when is it best to use polyfill?

The skinny on polyfill...

Pollyfil is a sound absorption, dampening fiber that will deepen bass, provide cleaner midrange, tone down any unwanted reverberation and improve the dynamic extension of any speaker system.

It does this by eliminating standing waves, which is something like an echo inside the box. The result is tighter, more accurate bass. It also helps to give a flatter frequency response to the overall sound, which is good. Besides this, it also helps reduce the vibration of the box, which results in less distortion.

Damping also increases subwoofer efficiency by dissipating some energy that affects the sub, particularly the voice coil. Pillow polyfill and fiberglass insulation are common, though polyfill is a lot easier on your skin. Polyfill also "tricks" a sub into thinking it is in a bigger box. Most sealed and vented enclosures require 1/2 lb. of dampening material per cubic foot of internal enclosure space. For best results it is recommended to loosely fill the material throughout the enclosure avoiding port or vent openings .

You can find polyfill at any craft store or the craft section in Wal-Mart, for those that want to know.

More info here http://spkrbox1.spaces.live.com/

Sparky has this question covered...

I will add that, for subs, using polyfill may not always make much of a difference in overall sound. It will slow down the sound waves which does trick the sub to thinking it is in a larger enclosure. The thing is that sealed enclosures are very forgiving on the overall internal volume. So an enclosure that is, say, 2 cubic foot would sound virtually identical to one that is 2.2 cubic foot for many subs.

I've used it in a few of my set ups to keep the "rear wave"(if you want to call it that) issues to a minimum. It works pretty well in my applications.