My first impression was that something was wrong with the hookup, but if you were listening at that moderate a level, maybe that was a reasonable result. Using about .64 watt would result in about a 89dB output from the M80 at 1 meter(neglecting room effects), which is comfortably loud. It'll be more interesting when you're able to turn it up into the problem levels.

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Enjoy the music, not the equipment.