Wierd sub noise

I bought two 10's from a friend and they worked really good but now anytime i turn up my music loud i start getting nasty distortion in the bass....It didn't do this before and at lower to medium levels it works fine. Anyone know what the problem might be???

have you taken the subs out of the box to see if they're visibly damaged in any way?

no i havent really had time to do anything i was asking first just to see if it might be a bad connection or something.

bad connection maybe, but doubtful.

what brand are they, and how much power are you giving them from what amp?