"70 volt" speaker systems would usually refer to ceiling PA system installations - you may notice a small transformer attached to each one. Its a technique used to string multiple speakers together using the transformers to control the amps load. The individual speakers (once the transformers are cut off, or bypassed, which you would have to do if it is not already done) are likely just pedestrian 4 or 8 ohm speakers. If the actual ohm rating is not noted on the magnet base, you could test them. In any case, I'd not use them for home stereo purposes regardless, as they would make a poor choice sound-wise. what is good for announcing bus arrivals is not necessarily good for home theater.Your amp sounds like it was likely pulled from a similar, possibly the same type of commercial installation. I cant think of any other reason to bother noting it can operate above 16 ohms.Home installations do not care about anything over 8 ohms or whether the unit operates in a mason jar burred in banana peels, or any of that guff. Any way, the real hat trick here is to operate below 4 ohms, which says something about the strength of the amp. These types of ceiling installations do not wire up the same way as home stereo. there's tricks to it. If you intend to rewire up such a system get a good installers book, or hire a pro.