Eminence Magnum 18LF. This driver is now discontinued and it is unfortunate because Eminence no longer appear to offer woofers with shorting rings in the motor like this one. It has a phase plug of sorts behind a wire mesh dust cap. It has ventilation holes and appears to serve as a means of cooling the motor.
Raw response measured nearfield:
You can see the impact of the high inductance above 700 Hz where it is causing roll off. The response above 1.5k appears to be influenced by breakup modes. In the range of frequencies of interest for a woofer it is nice and flat. Compared to the Peavey Black Widow that I was using previously, it has a more extended midrange response. The Peavey started rolling off earlier despite having a lower inductance. The sensitivity is slightly lower at 95 dB.
I haven't had a chance to integrate everything properly, the woofer is too far away from the horn to work as it should, but the first impression is that these will do very well.