I do run My M80s at 60hz and sometimes 40, but even at 40 it starts to get boomy. I guess if calibrated with 40 hz settings the boominess may go away, oh great, I have talked myself into even more tweaking . I finally have my old XP box back together and running so I will be experimenting with REW in the near future.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70