Hello mrihar,

The M80s normally have deep, extended bass output (not fat and boomy, but natural and uncolored), so something is wrong. Check your low-frequency crossover settings (bass management) in the AV receiver to make sure you have the M80s set on Full Range or "Large". If you were using the HEP500 sub previously, you may have set the M80s to "Small" with a crossover at 60 or 80 Hz, which is what we normally advise.

Regards,

Alan Lofft,
Axiom Resident Expert (Retired)