I have some Emilar EC320A. Radian came into being after Emilar ran into financial trouble. It uses a 3" aluminum diaphragm with a soft surround rather than a diamond shaped metal surround. The Radian drivers actually produce extended response from the dome rather than relying on parasitic resonances (e.g. JBL) from the surround to get extension past 10kHz. It acually does have extended response out to 20kHz that could be used with a shelving network. I can send you an image of my measured response if you send send your email. The only bad thing I have heard about the Radian drivers is that Sound Physics Labs switched from the Radian 475 to the B&C DE25 because the Radians couldn't withstand PA power levels at their rated power. For home use they should work fine.I was told that the 850 is the best model for home use, even smoother than the neodymium version. If you decide to buy, you may be able to save money by purchasing from Image Communications in Chicago, but they are still living in the 80s and don't have a website.
Bruce Edgar is using a 2" neo compression driver in his smaller horn system but I can't tell from the images if it is a Radian or a P. Audio driver.