Simple test. Keep amp off, then GENTLY spread your hand out over the cone on the bass/mid units and gently push them in and release. Not too far. If the bass or mid unit have problems then instead of allowing you to gently push the cone gently in they will grate. Be careful as you are not trying to stress them but more trying to determine if the coils have melted, If they have then they will grate. If not it could be tweeters.