Hi dbbx0,
MisFit Toy is correct. When you are not running a subwoofer and you boost the bass that much with the bass control, you are asking the H/K's amplifier to deliver at least three times as much power at low frequencies (if you are using 6 dB of bass boost, which would approximate your setting of the bass control). The H/K's protection circuit senses too much current flowing through the output transistors and shuts it down to prevent it from overheating or blowing the output transistors.
Get a subwoofer!! And if you like really deep bass that much (most people do), think about the Axiom EP500. It's spectacular.
Regards,
