Audio Systems: Subwoofers Cut Out, sony headunit, power cap

Question
I have two 12's Crossfire DB312's a alpine mrd-350 amp and a JVC headunit.  I
really don't remember having an issue last year when these were hooked up and I
gave them to my friend to use while I didnt' have a car...they worked fine never
cut out in his car he has a sony headunit...Well i put them back in my car and
the only thing different is the wires there new but the same as the old ones.
Now I feel like it cuts out when very loud when before I could turn it up to
where it was unbearable to sit in the car with it not cutting out.  There fine
for normal everyday sound but for some reason they'll cut when you turn it up
loud.  I was wondering if maybe it never did it in his car because my headunit
has a LOUD option which makes everything...LOUDER lol his does not.  Any
suggestions?

Answer
Premature amp cutting out can be due to a poor ground  (not down to good bare metal), 12v line too long, weak battery that cannot hold up when gut busting bass is needed, overheating of the amp caused by too low impedance, short on speaker line, etc.

You could probably benefit, after checking all the above, by adding a power cap at the amplifier.  This will help to hold up the voltage during big bass demands and take some load off the battery system.

Hope this helps,
Cleggsan