B-Quiet is a very inexpensive sound deadening material. (B-Quiet.com) I used Seam Sealer where the body pannels come together. It can be foud at automotive stores. Another thing I used was foam padding in my quarter pannels and any where else I could stuff it. I just used that pink egg carton looking foam for like a mattress. Get it at Wal-mart for $7-$8.
2006 Jeep Liberty
Adire Audio, Cadence, Clarion, MB Quart
Lv = [(14630000 x R^2) / (Fb^2 x Vb)] - 1.463R
*Vb = vol. in cu"
**R = sq.rt. A / Pi (for square/slot port)