I just installed a kenwood kac-8405 720w, it has speaker level input built in. I hooked up the 4 speakers to the included harness, no subwoofer, and the auto-sense on/off works (amp lights go on and off with the car) but there is no sound difference. The adjustments on the amp do nothing. My speakers are pioneer 260w max 50w rms, and they sound good but while music was playing I unplugged and plugged in the harness from the amp and there as no sound difference. I also tried a scosche output converter just with the front left speaker to see if I could then adjust the gain or use bass boost or ANYTHING that would verify the amp is doing something, but nothing.
With speaker level input are gain adjustments and things like bass boost just not adjustable? Logically the speaker level input is just that, an input, so if I'm not using the output section of the amp I don't understand how it's doing anything. Any information would be great.