What has blown my tweeter????

I turned on my system this afternoon and noticed to my major dismay that the tweeter on one of my speakers, (JMLab Megane Carat), has totally disappeared! I always listen at
reasonable volumes, (between 7 and 15, out of 60, on the Classe Cap 101 Led), and I listen primarily to classical and jazz.

Does anyone have an idea as to why the tweeter would get up and disappear like this? What normaly causes tweeters to blow?

Thanks for any and all help.