JL HD600/4 problem
 

ive got a JL hd 600/4 powering all four of my components and every once in a while at higher volumes itll go into protect. grounds are good. my deck shows power is around 14volts when it goes into protect. what could the problem be? ive got 4ohms load in the rear, and a 2.7ohm load in the front so all well within what the amp can take. ive also tuned everything using a multimeter so i dont think its clipping anywhere. ive also got a HD 750/1 powering my sub and it never goes into protect even when the 4 channel does the sub still plays. could it be a dying speaker? i dont think its over heating seeing as its real cold out. any help would be great. thanks