Vintage Norelco Speakers

Looking for insight on a vintage pair of Norelco speakers. I'm not sure the year and what to use to power these babies. They are a linear array with 6 six inch speakers in each cabinet. There is a knob on the back that rotates from 1 to 6. Not sure how it's used. The model on the back of the speaker magnet is AD 3700 M. Any help would be appreciated. Thanks