Hey, '91. I thought I would take a chance with a Rockbox, just like you suggested. Installed it tonight, took about 90 minutes (it could have been quicker but I was very careful!). Verdict? Works great!
I didn't take any pictures, but here is what I did. (Note - this is not a recommendation, just a decription of what I did to the rear RHS speaker in a '92 vert).
There are 4 wires going to the bose speaker. I had black, orange and two shades of blue. Using a voltmeter worked out that the orange is positive, black negative (measures 12v across them when the radio is switched on).
I had no idea which of the blue wires was positive for the speaker, because the old speaker amp had blown up and I couldn't trace the old connections. Trial and error then..
(for all the connections below I used some snap-fit wire connectors that I bought 20 years ago in the UK. Just lay two pieces of wire across them, close the connector, and it connects and secures the wires. Haven't seen them in the US yet. With these, I didn't need to take the amp apart or do any soldering.). Note that the amp comes with all external wires supplied.
I decided to use the Bose speaker internal wiring loom for the connections, but can't remember exactly what colours they were. Therefore all connections described here are relative to the wires going to the bose speaker unit.
Connected orange (vette) to red (rockbox) and black (v) to black (rb). The Rockbox (rb) has a third power lead (orange) which I connected to orange (v) too. This meant the amp's green light came on when I switched on the radio.
I used an old RCA connector (the sort used on home hi-fi) and split the wire to use just the right channel. Then I split the wire again (signal and shield). I wrapped electrical tape around the shield wires so it would work with the snap-connectors. I had no idea which of the blue (v) wires was signal, so I tried it one way (which, when I first tested the amp, caused the speaker to pulse. The other way worked fine). I checked my notes and didn't record which of the wires was signal - sorry!
After that it was easy - the amp (rb) comes with speaker wires and I just connected these to the old speaker wires. The rb easily identifies + and -, the bose speaker has a "+" scratched next to one of the connectors.
The rb comes with a filter switch, I left it set to off. It also has a 'level' control. I adjusted it a few times until I was happy with the balance of sound levels between the two rear speakers.
In terms of fitting the amp inside the speaker box, I had to snap off a couple of fitting lugs from the speaker. I used two screws to hold it on - but it may not be enough in the long term so I might take it apart again over the winter and find a better way of fixing it.
Put it all back together - works great. Only two things.. I notice that the rb expects speakers with 4 ohms, I think I read somewhere that the Bose speakers are 1 ohm. Also, since I installed the amp I think I can hear electrical hum at very low volume. '91 - did you notice this too?
Anyway, this may be useful for someone. Remember, it's not a recommendation, just what I did.
Andy.
