Bought these on a whim, they seem to need service. they have the MK 121 interfaces, and play very softly. I have to crank the receiver volume up to overload levels to hear the speakers. I don't think I have the knowhow to fix these. WOuld like to pass them on to someone that knows how to repair them. Seems like it could be a transformer problem. Panels seem to work fine. Large speakers, pick up would be best. Located in San Francico Bay Area