I recently moved into a house with ceiling speakers and an impedance matching (I think) volume control in each room. There are probably 10 sets in all that are wired to a simple patch panel in the attic, and a master set of input speaker wires is in the family room.

I have a Sony STR-DA5000ES receiver that I'd like to use to run them, but I have a question. When I put a multimeter on the master wires in the family room (to which I'd hook the receiver) they show roughly 50 Ohms.

Will I be OK using the Sony, or will it be a dangerous proposition to hook it up as I've described?

I should mention that I bought the house from the second owners, who were total luddites, so I have no idea of how the system was used or with what it was driven by the original owners.

High impedances will not do any damage whatsoever. It is low impedances you have to worry about. The only problem is, you may not be able to get it loud enough. Won't hurt to try though.

http://www.alectrosystems.com/audio/Distribution/70volt.htm

The pictures and info at the link left by MLKstudios made me think that a picture might be worth a thousand words.

This is the control that's in each room. I can't find a brand on them - do they look familiar to anyone?

I haven't pulled one of the speakers to see if there's a transformer on it - could this be a 70v system?