[ KB ] JBL audio system specs and measurements

Good article, good useful information. I would suggest converting to PDF and posting the PDF itself.

It is clear that the outputs are not flat, but as one poster commented, it could be to compensate for the acoustics of the car.
Someone else posted a picture of the circuit board from overhead, you may want to include that. The 'power transistors' are probably power amp ICs. I really doubt it can be a 7 channel (FRW, FLW, FRT, FLT, C, RR, RL) discrete push-pull amplifier. That would require at least 14 power transistors, and there just isn't enough room for that.