Brian, you're reaching. If there's any weakness in the 60-80Hz area(measured?)it could possibly be due to a room null which would affect any speakers, but certainly isn't due to either your PB12-NSD or your M22s if you're using a 80Hz crossover. The M22 enclosure is tuned to about 55Hz and response is strong to well below 80Hz. The PB12-NSD has strong response to well over 100Hz(not 60Hz). The combination makes for an excellent blend in the area you mention.

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Enjoy the music, not the equipment.