JBL had their own beryllium, mainly used on 476, 435, etc. Do you have 476?
TAD have their own, and others use Truextent beryllium, including with many JBL drivers. Beryllium can get hot but it is a bit like an electrostat. Very see through and transparent, and upstream can affect it a lot. I like it because of the transparency (both see through and to upstream gear and recordings), ease, and their resolution is highest for large scale orchestra is the highest. The music is just there. With paper, despite the lovely tone, it is the tone of the driver, and large scale congests. Though I am not comparing the same driver with diaphragm swapped, but essentially the beryllium drivers of TAD and Radian to other non beryllium, so there might be other things. Nuance is also very high