Customer has an old 70v amp. It's not sending constant power, only when a page is sent to it. Works great.
They want to add three speakers to it. Assuming the load capacity is okay, what type of wiring should I install? I was thinking 18awg shielded. Any suggestions?

18ga is fine as long as you are not talking about high wattage and or long runs. You don't want to use shielded.

-Hal