B-52 AT 412 Speaker Cabinets Technical info - Re:What is the correct impedance selection? The cabinet is switchable mono/stereo...with two input jacks. 1 for 16ohms and the other is for 4 ohms. My amplifier (head) external speaker jack requires a "minimum 8 ohm load." By the way, the speakers are rated at 120w/each, giving the cabinet a 480W rating.