The 12" is based on an Eminence driver (as far as I recall Beta 12 - but mind you, I could be wrong!). But it's highly modified - another VC and diaphragm system - think the only left of the original Eminence is the basket and the magnet. I don't know the X-over frequency, but since the Hammer 12 uses a kind of whizzer, 10kHz seems plausible. I think they changed the type of super tweeter they use recently...