Xavier, welcome. Quite some time ago both Randy and I commented on a sudden 3 or 4dB increase in the sensitivity specs of several models(not including the M80). Axiom didn't clarify the situation. The present decrease in the M80 spec raises the same question. The present sensitivities shown here
indicate that the M50 and M60 are now significantly more sensitive than the M80, which seems unlikely.
Axiom should clarify if these measurements are under different conditions(and therefore not useful for comparisons), rather than indicating a significant change in the actual sensitivities.