Can I use a multimeter to measure audio signals by testing amperage or voltage?

Question

I'm in the process of adding a subwoofer to my car. In doing so I spliced in a T harness to audio wires from the head unit and routed the wiring to where I Will be placing the Amp. I tested the speakers after that using the balance/fade settings from the head unit; all channels work as expected.

In the interest of future proofing my wiring I tapped all four speaker channels, that way if I decide to add a four channel amp I don't have to rerun another wire set. Unfortunately with four speaker wire sets, I didn't keep track of which is which, and need to verify which wire-pair belongs to which speaker channel.

I was wondering if I could use the balance/fade settings on my head unit and a multimeter to determine which speaker wire is which channel. I can set it up so only one speaker is active at a time and test the wire pairs with my multimeter, but I'm not sure if I should be looking at voltage, amperage, or both.

Answer 1

Switch to AC volts and crank up the music. Monitor the voltage at the splice.

Alternatively disconnect from the amplifier at the splice and attach a 1.5 V battery to each pair in turn. You should hear a little thump from the connected speaker as the DC kicks the coil slightly.