Good to hear!!! The way the multimeter works is if you turn the radio on, connect the multimeter prongs to the speaker-level wire outputs from the amplifier. Reverse polarity produces negative results, and the correct polarity produces positive results. Pics attached as I just performed this.A huge thanks to all who answered. I tried two multimeters without success. But I’m learning and your detailed reply is so appreciated! The 9volt battery suggestion worked like a charm. The old raggedy sub jumped up like a rabbit! Many many thanks to ALL.