Audio Systems: Car audio problems, impedance mismatch, speaker unit

Question
Hey there,

I have a car system that the subs kept cutting off and then back on then all sudden cut off for good. the speakers and amp are fine. i am thinking it is the fuse by the battery can you help

Answer
It is more likely the amp going into protection mode from:

ONE: Overdriving the subs with too much power.
TWO: Fuse too small for the current required - if the fuse is blowing.
THREE:  An impedance mismatch between amp and speakers (for example, if the speakers are DVC giving 2 ohms impedance and the amp is good for 4 ohm load it can cause this to happen).
FOUR: A shorted condition in one of the speaker lines between amp and speaker unit.  Disconnect one sub at a time to see if it helps.
FIVE:  Bad ground for the amp.  Check it to make sure you have good solid ohmic connection to the chassis.  Chassis ground spot should be sanded down to bare metal and ground wire bolted or screwed solidly to the bare metal.

Let me know if you need more.

PS: Lastly, could be, if amps and speakers are drawing too much current from the system that the 12v is dropping too low causing the amp to drop out.  Same thing if the 12v line from battery to amp is too small causing big voltage drop under high power conditions.