Help with my friends system

[derek33 10+ year member]

My friend has my old system in his audi a6.

2 amps, 2 subs. 1 amp to each sub. pretty basic.

its been in there for 3 or 4 months, and everything has worked fine.

lately one of the subs pulsates for no reason. it sounds like a heart beat.

Its only one amp/sub that does it. and its the "2nd" amp, it is the one that is muching off the first amp. (rca from headunit goes to the first amp, then the rca goes from the first to the second)

any idea whats causing this?

thanks

Click to read more...