John, the best process is to go through everything to eliminate variables.

Does your dad live close enough to bring his speakers to your house for comparison there, as well as bringing your speakers to HIS house to compare on his system?

You need to confirm that both tweeters are working and that the system is not imparting a change of sound.

Comparing the new M3s to the old ones is beneficial in removing variables.

::::::: No disrespect to Axiom, but my favorite woofer is my yellow lab :::::::