Horns: Why don't they image well?

Anyone have a theory?

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I love my Heresy III , unfortunately they've been boxed up for 6 months...  just got them to my new place and am picking up a nice BDI rack in the morning...  can't wait to fire them back up this weekend.   They sound way better than that Altec blutooth speaker I've been using.
Anytime you use a giant waveguide to spread high frequencies you are trading off a large soundstage (flat power response) with less precise imaging (since the highs are getting stretched over a wider area).
As I mentioned earlier there is a new Klipsch La Scala.  It is the model AL5.
Watch this folks....

I came to this thread really opposed to horns, and I'm not 100% on them today, but I'm not going to let the misinformation go unchallenged. 

Horns don't "spread the sound". They mechanically couple a pressure impulse to the environment. Horns are MORE directional than dynamic drivers with more controlled dispersion. 
Partly correct, but for many years horn systems have included "phase plugs" or their equivalent to keep horns from "beaming" high frequencies. The high end horn systems I use for pro sound are designed to spread high frequencies over a large area, and they do that well, and the Klipsch Heresy IIIs I use in my home system easily have as good or better dispersion of high frequencies than the dynamic speakers I've owned over the years.