Avalon Acoustics?

Manufacturers End of life drivers a lot of times. And speaker makers have no choice but to source new ones.  Are you talking about the C90-6-079 (vs the old 078) mid or the D20N6-31 tweeter?
if they use a 12dB per octave crossover I am certain they’d have to reverse the polarity and notate that the red dot.  

Samgar2 If your replacement mid is 1/4” higher then there would be trouble mounting into the cabinet. 
Note the black goo they use to get the back of the driver to mount flush against the supporting stud inside the cabinet.  If the new mid is indeed thicker it would spread the goo all over the place causing a mess.  

@missioncoonery   You're right on the money.  I remember a few years ago the price for Isis speakers which was already substantial jumped 50% in a couple of years for no apparent reason.  Avalon prices now aren't even in the ballpark of being competitive with other speaker manufacturers and so the company has become irrelevant. 

Yes, there was trouble with mounting the new mid range in the Isis speaker and it's deeper thickness did break the the silicone ring and also forced the back glue all over the back. Although they have a beautiful looking speaker their prices have become out of control and they are no longer competitive with other great sounding speakers.