I thought I'd share this with you guys. It gets a little technical, but those people that are into designing the perfect sub enclosure might find it interesting/helpfull.

http://diyaudiocorner.tripod.com/dilemma.htm

I was doing some research on sub box filler materials when I ran across this. I've got a 15 in a BIG box that I'm experimenting with

 

Just an FYI with the filler material.

I have a BIG ported enclosure for a 15. Somewhere around 6.5 cubic feet. The reason for the size is I was trying to emulate what the 15 sounded like in the trunk of my old Buick Lesabre. Anyway, the setup sounded too boomy and had pretty hollow hit to it. I was trying to eat up some air space and eliminate some of the hollowness. Well, I just got done putting an old queen size comforter and a pillow case stuffed with those plastic bags you get from the grocery store in it. I have to say I was impressed. It doesn't hit quite as hard on the rock type bass as I would like, but when it comes to rap it's right on the money. If I put a 10 in a sealed box back there with it I would probably be pretty satisfied with it. My one 15 now hits and booms as hard as 2 15's in my buick did.

Edit: This is in an Expedition btw.

 

Its nice to see someone actually explaining Qtc as it is one of the most important factors regarding subwoofer performance and system planning.