Speakers going fuzzy?

[nikz]

So a while ago i bought some pioneer mids and tweeters for the car which are not amped (I already have a sub and amp). For the couple of months I had them they were working fine, now recently they begin to go fuzzy and distorted after driving for about 30 mins at my standard, quite high, volume. The treble seems to just become distorted. Anyone have any ideas on what the problem may be? Or do i just need to get the speakers amped in order to work at the "normal" volume level I have? /

Thanks in advance for any help.