I have a single 12" sub in an enclosure in the back of my JK. When I turn up the music or it hits a certain frequency it makes a rattle. Is the sub blown our is my enclosure not big enough out is about a 2x2 cubic foot box.

 

you need to be more detailed...what sub are u running, what amp, the box is 2x2? or 2 cubic feet?

 

is it the sub rattling or is it something else?

 

It is an Insignia sub, I know out is not the best, I have owned rocksford and kicker but it was cheap and a gift. The box is 1.5 ft wide,.2 ft high, and 2 ft wide the other way

 

It is definitely the sub.

 

That seems like a pretty big sealed box for one 12. i dont know about "insignia" but most 12" mid grade subs are good at around 1 cubic foot of airspace. Just for referance that is 12"x12"x12" interior space after sub displacement. hope this helps...there alot of decent box designs on the web for vented subs if that is what u were looking for too.