It is written on their web page that they use Radian drivers. The 1" Radian with be diaphragm is 475be-pb. I have the beryllium version of this driver with a very similar horn (mine is jmlc 1400hz, universum has jmlc 1500hz, and from the same material). 475be is a good driver, and I heard it against TAD 2001. TAD is a "tad" better but not much and like them. I use Radian on the midrange and prefer to have family synergy.
Sami - is the uni mid range also a Le Cleach?