Paul, since the external connections seem to be correct, there's a possibility that one (or highly unlikely both)of the M80 woofers has one of the internal wires loose and it isn't working. Test the speakers one at a time on a piece of music that has good bass, and remove the connecting strips so that the speaker wire is connected only to the lower woofer terminals. See if bassy sound is heard from each M80.

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Enjoy the music, not the equipment.