There's a complicated subject, and I'm not a speaker designer by any means.
Basically, dome tweeters are point sources, meaning that the sound pressure waves emanate from a unidirectional dome that is small enough it can be considered a point. Hence the name, a point source. There are several kinds of drivers, like ribbons, planar magnetics, leafs, electrostatics, and (I think) AMTs, that radiate sound along the length of a driver. With the RAAL ribbon it's several inches of length, with full-range electrostatics it's several feet of length. The radiation properties of these line source drivers have much different room interaction effects than point sources, which is one reason why they sound different.
There are several different kinds of line source drivers, and their radiation looks like a cylinder or some fraction of it. Most drivers that have full cylinder radiation have the rear 180 degrees out of phase with the front (like electrostatics), because the same two-dimensional driver surface is radiating in both directions which further makes them sound different. My sense is that a good line source with a back wave can be charismatic, and I seem to fall for the effect a lot. I also fell for it with the Quad ESL-63, but that speaker doesn't have much in the way of bass. The old Infinity Reference things were planar line sources with cone woofers were another example.
Line source speakers that are open back tend to dominate a room, since they need to be several feet from the back wall. Most are also not suitable for HT systems playing action movies, though I know someone who uses Martin Logan hybrids for his HT system, and thinks anything with a dome tweeter is dumb.
Then there's line arrays, which are a long column of point source drivers, like the Funk Audio thing referenced earlier. They radiate as front-only cylinders (the cabinet catches the back wave). I've never heard one before, but they have a cult following too. Some people are really attracted by the effects of a tall wave front.
