Option 1: there is one 4 conductor wire for each set of speakers in the house. If there are 6 pair, there are 6 4 conductor wires at the head end. Each 4 conductor wire goes to a vc, and a separate 4 conductor wire goes on into the walls to speakers. Pull two conductors off for first speaker, pull second two conductors off for second speaker. Use impedance match vc's or a speaker selector with impedance matching to protect amp.
Option 2: there is one 4 conductor wire at the head end. It goes to a vc location. Each of the vc locations have 4 conductor in, and 4 conductor out. You will need to use your toner to determine which room is the first in the chain, and which is second, and so on. Using impedance matching volume controls to protect the amp, you will need to retrofit speaker wiring to each vc to feed speakers in the room. Easiest would be to put a wall plate below the vc with speaker terminals and use box speakers in the room connected to that plate.
