This might apply to 1990-1995 Bonneville SSE and SSEi'* with the 4-wires connectors at the rear 6x9'* -if someone with a 1990-1991 SSE and someone with a 1992-1995 SSE/SSEi wouldn't mind verifying this info I'm sure it will help many.

Well, when I pulled my blown rear speakers last night from my 1998 SSE with the BOSE Dynamic Equalization I found something interesting. I had looked for speaker adapters for the BOSE speaker connectors back when I was looking to replace the 6x9'* in my 1999 SSEi and was told there was no such adapter.
I can now say there is a wiring adapter to hook up to aftermarket speakers, and you already have it. Apparently Pontiac had one made to hook up to the BOSE speakers.

Here'* what I found:

interesting!

what was i thinking!!! oh well

who would have thought

what does this really mean? does that adapter run both the full range and gain signals (4 wires) straight into the two wires shown? Does this mean I can get that wire and plug out of a Bose car and get some aftermarket 6x9s and retain my gain control?

Or is there something special about the Bose speaker that allows the 4 to 2 wire splice to work?

If I'm reading OlBlueEyes' post correctly, he was looking for an adaptor from the factory connector to an aftermarket speaker. It was hiding in plain sight.

The connector in my 93 speakers is similar except the wires are soldered instead of having the female connectors. Unlike the vehicles equipped with a gain slider, the Bose equipped vehicles do not use the dual voice coil 6x9s and are therefore "aftermarket ready". The connectors can be cut from the DVC speakers and female connectors can be crimpped on to accomidate and aftermarket speaker. It'* important to note that the correct pair of wires would have to be identified as there is two pairs of red and black wires. You would want to connect the aftermarket speakers to the full range output. The other pair could also be used as a high level input for a sub amp if desired.