thanks! that all helps alot. viridian, i will try that, but i am unsure what the dust cap is exactly. rockvirgo, my sub has 2 eight inch woofers, one DOES make that crack, i have described it as a smacking. the other does not. therefor i ponder whethter one is dmged or not. i feel like it is bottoming out, but not sure. thanks again all.
