i have an HK4000D MAaudio amplifier. i hooked it up and... no sound...it turns on like normal, but no sound comes out of the sub... when i try to cross the speaker wires it doesnt short out... do i have a defective amp? is there no sound going to the amp mabe so hence nothing going to sub? is there an option on my kenwood KDC-MP232 headunit to turn on the sound going to the amp? thanks