my buddy hooked me up with his schroeder 212 cab. i waa looking for a cab for shows that is light yet powerful. tested it today with darkglass mt500 and it sounded amazing. the bass is a squier bass i hot for $80 and had it repainted then put highway one electroncs in it plus an omega bridge. it is badass. got the cab for 5 bills and i think it was a badass deal. anyone have the same cab if do what does the knob in the back of the can do?