I don't know an incredible lot about the stock system other than this:
Cassette HU w/equalizer & gain adjustment
5.25"'* + seperate tweeters in front
6X9''* & seperate tweeters in rear.
It is this last bit that has thrown me. I've been doing thread searches and can only remember one other person mentioning the stock rears having a seperate tweeter.
What I'd like to know is: Is there a crossover, or are they just running from HU to 6X9 to a piggy-backed tweeter(kind of what it looks like)?
If so, is this the crossover for them, or is it just the compass sensor?
This Black Box is located equidistant between the rear speakers in the trunk, but too far forward to have anything to do with the rear brake light, so far as I can tell.