Subwoofers cutting out

I have a 94 taurus gl and I have a kenwood sound system in it. I have 2 12" subs (kenwood tornados) and a 600 watt kenwood amp and it always cuts out and just stops playing the bass. I was wondering if anyone would have any ideas what this could be.

Cd skipping? Loss of power, bad connection? any of the above?

if it's just the bass speakers ...... either you have loose power wires or something is tripping the protection circuit - like the load on the amp is too low, or it's overheating or something like that