popping noise- 6x9's??...... help

[disceptre420]

i have 2 15's in my buick lesabre. whenever i have i turned up loud enough (and it seems like only on really deep notes) i get a popping sound. its really bad and i cant even stand to listen to it.

i think i narrowed it down to the 6x9's because if i unmount them from the shelf and just lay them in the trunk the noise goes away( there still plugged in.) or if i open my trunk the noise goes away (even when they are mounted on the shelf)

today, i took my back seat out and just layed them in the hole in the shelf, and put it all back together to see if it might be a pressure problem. it seems like it may have helped a bit but its still there

anybody know whats going on?

[kovemaster559]

use a xover on the 6x9s or make boxes for them

[disceptre420]

so whats happening and what will the X overs do. ( i never have used X overs)