Poly-Fill ?

i've never heard a big difference, but i have a friend that swears by the stuff. supposed to slow down the sound waves or some-such. if it does, slower soundwaves make deeper tones. hence, lower bass.

although i can't tell for sure either way, there's nothing wrong with a little experimentation on your own part. you can get a big bag of the stuff in walmarts craft section for like $3. if you try it, make sure you let us know your take on it.

cheers

To absorb internal standing waves and to prevent reflections into the woofer cone, some sort of acoustic dampening material such as poly-fill should be added.  Adding this material to an enclosure will increase the apparent internal volume. This is important to note, especially with sealed box designs, since the enclosure should be filled close to 100% and equivalent volume increases of 10 to 25% are possible depending on the amount and type of material used, so you must undervolume the enclosure to achieve our target.  For example, calculate the target volume of the enclosure and then undersize by 10% when you build it, and add a pound of poly-fill for every 1 cuft of enclosure volume.  This will allow you to build a somewhat smaller enclosure for a given woofer.

Adding polyfill can increase the "apparent" box size by up to ~20% in a sealed enclosure. More than lining the walls of a ported enclosure may do more harm than good.

  http://www.win.net/audtatious/audio/fiber.html

  http://www.geocities.com/kreskovs/Box-1.html

Read and enjoy.