a horn-loaded design that i'm curious about is the hedlund horn.
http://www.adminsoft.ch/Hedlund/HedStart.htm
this is designed for the lowthers, or the aer driver, which is basically a german-made lowther knock-off, that's supposed to best the lowthers in all areas.(perhaps addressing your concerns, lak?)
the hammer s-12 - a wery interesting concept, really isn't truly full-range; it goes from ~45hz to 11khz, & uses a x-over w/a supertweeter.