Hi all. I recently bought a used Dr Bass BL 212 600 Watt 2 Ohm cab. Sounds great with my AI Clarus SL amp + Fishman Pro-EQ Platinum. But, there is knob on the back of the cab and I’m not sure what it controls. Maybe balance between Tweeter & Woofers? I hear no change between 7 o’clock and 5...