Using a loose material such as polyester fiberfill and eggcrate foam are two different things. Using eggcrate foam will definately make your box smaller.

 

Believe it or not, the fibers in polyester fiberfill 'wiggle' from the energy created by the subwoofer moving. That movement dissipates energy which is what makes the sub act as if it is in a larger box. I doubt the density of the eggcrate foam would allow for the same effect.

 

Eggcrate foam works fantastically for cancelling reflections inside an enclosure. I stuck my hear inside and enclosure before and after a lined it and talked to myself - the different was stunning.

Look in the yellow pages under Foam - there is a little shop here in Burlington on Brant St that I get mine from - and another on Plains road when I need a backup.

 

It's polyester fiberfill or more commonly known as pillow stuffing. You can use other stuff but it usually has more negative properties. For example fiberglass insulation will work as well, but has a tendency to make you itch and could possibly get into the inner workings of the sub. I have heard of using lamb's wool as well, but that costs a fortune. I don't know about the effectiveness of using eggcrate foam, I only used it once and it was more for cosmetics of having a plexi back on the wall. I know it has a pronounced effect when talking into the enclosure, but that isn't really the frequency range that would normally be bouncing around in there. I am going to make use of alot of different acoustic foams in my Beetle, but most of it won't be in the enclosures.