Horns: Why don't they image well?

Horns tend to give a wall of sound, but rarely can image pinpoint in the horizontal and vertical and depth like the above ones mentioned can.

This statement is simply false.

It may be true for some earlier horns as the throat design and curvature of the horn flare affect its response. These days that is optimized with CAD; horns can image as well as any other tech.

I own a customized pair of Avantgarde Uno's (pre 2006) that produce a wonderful soundstage...

As a follow-up to my suggestion above of horns imaging "differently," it's not meant to imply they do so 'per se,' but rather in comparison to a range of direct radiating speakers - I believe that's very important to point out. Really what it comes down to for me is the sensation of uninhibitedness as a desirable trait, and I gather imaging is if not irrelevant, then a part of the overall "equation" that comes to life largely via presence, dynamics and ease as something more substantial and dense in quality horn speakers; this, to me, typically imparts other terms of describing the sound as "imaging." 

horns can image as well as any other tech.

This is a false statement.

Klipsch, set up correctly, they can " disappear " as well as any other design. However, imaging and sound staging are not the attributes that I enjoy most about them

+1 MrD

"Wall of sound", and "image/depth placement" to me are separate identities.
"Wall of sound" is heard not really seen eg: Horns, Headphones.
"Image and depth placement" is seen and heard, ribbons, esl's, ect.    

Any diffuser that radiates the sound so it's splashes/spreads the sound left and right across the room and will also gives added room reflections, will give a "wall of sound" effect which is pleasing to some (aka Bose 901's). But will totally trash precise image placement and depth perception.

This was demo'ed to us the whole range of Magnepan speakers and Klipsch K-Horns, the best "imaging/depth perception" one was the narrowest Maggie, but it was also only a one man hot seat, the worst was the Maggie Tympani and the K-Horn which were the largest "wall of sound" effect, but as for "image and depth" perception their was virtually none.

Also if an owner puts all his gear on stands in between the speakers, is asking to diminish his image and depth perception.
The great Nevile Thiel (rip) once told me this and he was right, once I shifted all the gear to the side instead I never look back, no matter how nice and glitzy it looked in between the speakers.

Cheers George