Did you check your polarity between the L&R? The M80 can sound pretty good even with reversed polarity.
Did you check the individual drivers for free movement, no noise/drag?
Bi-amped with a dead channel?
Loose wire?

The quality of the recording is paramount too...did you check the output settings in your playback device?

Last edited by brwsaw; 02/07/18 01:38 AM.