aren't Accuton chassis made of ceramic?
 The Accuton concave domes are made of the following materials: 
Ceramic - for bass-midrange, midrange and tweeter drivers
Diamond - for midrange and tweeter drivers
Ceramic Sandwich - for larger bass drivers and passive radiators
Aluminum - for passive radiators 
I believe the chassis (baskets) are cast from aluminum or an aluminum-magnesium alloy. 
All of the speakers I have seen with Accuton midranges and tweeters have used the ceramic models.  I would doubt any of us could afford the diamond tweeters.  Madisound primarily sells the ceramic and sandwich drivers, but they do list one 3/4" diamond tweeter for $2900. 
Steve