Basic Troubleshooting: 4 channel automobile system.

Hi All,

I am trying to troubleshoot a problem I am having with one of the channels in my automobile 4 channel (stereo w/front and rear) system. It’s a typical layout: Head unit with pre-outs connected to an auxiliary amplifier for more power. The front speakers are 8" mids with separate tweeters. The rear are very small (maybe 3") to round out the sound and give a little more dimension in my small 2 seat sport car interior. The auxiliary amp had to be adjusted to respect the small power capacity of the rear speakers and their limited frequency range. The overall effect is nice. Lately, the right rear speaker will intermittently get very loud compared to the left one which performs normally. I tested the situation by swapping right rear RCA to left rear RCA connector (connectors from head unit out, to aux amp in) and the problem reversed itself with the left rear getting too loud. Can I assume from this that it is not a problem with the wires/connectors or the speaker itself. The problem must be in the aux amp (perhaps the adjustment circuit has failed. The small speaker sounds like it is receiving lower frequencies it shouldn’t).... Or could the problem be in the head unit? My guess is that it is the auxiliary power amp. As stated above, the adjustments made in that amp had to be pretty extreme to limit the frequencies and power going to those tiny rear speakers. In fact before the proper crossover settings were made, both rear speakers were so over driven that I used the front/rear fade control in the head unit to take the heat off of them.  Another reason why I feel it's probably the aux. power amp... because that is where the adjustments are for each channel.  FYI: that aux power amp is 6 years old and is made by JL audio.

Any thoughts on my assumption here, given the information provided?