ok, i need to know some more info......... first, take a pic of the sub. what year model is it? if i read your earlier post right, you say that your friend hooked op a jumper between both black terminals, and hooked both red terminals to the amp? (one red on (-) and one on(+)? if so, did you try to get it playing loud for a bit? if that scenario happened, you can definitely heat the coil up quick and it will rip itself apart, or at least start to. and, yes, if that started, the loose parts of the coil will rattle like a snare. listen to the sub more in depth, or describe better. does it make a snare sound with the bass thump? does it kind of make a the rattling at low volumes, but go away when you crank it? is it more of a dull rattle, like a cell-phone rattling on the table? these subs are more difficult to repair than most, but not impossible. i would be willing to donate free labor to fix it for you, too, just need to know a lot more specifics about what happened, and what is going on........oh, and does it smell burned?