Johnk --
Thank you for initiating this thread.
In response to some of the comments above: horn and waveguide-based speakers span many varieties and combinations, just like direct radiating speakers, perhaps even more so; it would seem rather ignorant and unfair to generalize on their sonic shortcomings under simple banners going by the wide field they represent.
These last years I've concentrated solely on waveguide-based speakers, at first via dome tweeters (Amphion and eventually S.P. Technology/Aether Audio) and now from compression drivers through conical OSWG waveguides. Waveguides, particularly in the (exponential) shape of S.P. Tech and not least the 12" conical Earl Geddes-based OSWG's (from a Polish manufacturer) now in use for some years in my setup, bring along a much needed "fullness," coherency, and stress-free imprinting that makes direct radiating alternatives appear strained and thin - even malnourished. This is a very general imprinting, indeed. Add in a compression driver instead (of a dome tweeter) and the very important sense of effortlessness kick's in in spades; it's at once a sound more relaxed and fast, more true to tone, clearer, more saturated, and with a very addictive "fill."
Reading this review from 6moons of the British Harbeth M30.1 made me see, at least in the written description, some striking similarities in how I perceive the overall sonic imprinting of the waveguide-based speakers in mention:
I once mentioned how Harbeth speakers interface differently with the listening room than traditional boxes. Because their enclosures resonate to play an important role as acoustic generators, their sound emits across a fairly wide field more so than usual. The result is a type of sphere or warm sound bubble with us at the center. There is no high selectivity or detail as those terms are commonly understood. The sounds are clear, fluid and rounded rather than pointy and angular.
http://www.6moons.com/audioreviews/harbeth5/3.htmlIt would seem the sheer envelope of air displacement (i.e.: its radiating area) and radiation pattern (via Constant Directivity) plays a vital importance here, but also the fact that, in this combination, only one cross-over point is used, fairly low at that (some 1.3kHz), to a 12" rather lightweight paper cone mid/bass unit. In tandem with a 12" conical OSWG waveguide this makes for excellent energy coherence, and hence a sound many has described to emulate closely that of electrostatic speakers (notably Quad's).
I never experienced shouty or beaming tendencies from my speakers (what many find to be the typical negative side-effects from this realm of speakers), but it's definately more direct (yet still relaxed) than your typical "hifi" speakers. I can understand why some would find this "type" of sound taking some time getting used to, if they even do, when ones reference is mainly of direct radiating alternatives. I guess it boils down to taste in some respect, not least going by the overall mode of sonic presentation. To each their own..