I have run audio ciurcuits in a new house using 1/4" phone jacks interconnected from room to room - channel A and B so you could connect speakers at any point and still get the stereo separation between them. In one room you'd have your equipment connected to the matrix using a 1/4" inch plug per channel. So that signal would be at ALL the channel A terminals. So one speaker would be at say 8 ohms impedance. If you connected another speaker along the same line, it would be another 8 ohms in parallel which would lag down your system so you'd have to calculate an appropriate resistor to insert in the line to bring the impedance back to 8 ohms,
Total Resistance would be 8 ohms in parallel divided by 2 or 4 ohms. A 4 ohm resistor would be have to included in series to bring the impedance back to 8 ohms. Some systems are forgiving, other not.
