I have two 8” optional sub’s behind the rear seat in my 2004 C70. imo they are rather worthless as they don’t seem to get enough power to punch. I pulled them out and inspected it all – they appear to have some kind of sealed crossover (one per sub) and apparently are being driven by the 4x100 amp in the trunk. I would like to drop in a subwoofer amp and passive crossover and tweak it to my listening levels. Does anyone have a schematic to the wires running into and out of the crossovers ? I don’t want to blindly rip off the Volvo clips and bare the wires and start guessing, but I will if it comes to it.