My understanding is that the horn tweeter, as described by Steve in his first
articles regarding the Imperial - 'Hell, those aren't big', was a cosmetic addition
to the Speaker, not the ultimate must have or the Imperial wont work, tweeter.
Indeed, the article goes on to say that using appropiate drivers, the Imperial
has a wide audio range and could be operated as a stand alone unit.
None the less, as in my case, not having the PA type 15" drivers, the use of
an electronic crossover secured the high frequency stuff to a set of array
speakers I built some years ago, and the results were amazing.

Yes, the horn tweeters look fantastic, yes they are optional, and using simple math
to generate the parabolic curve of the horn, you can design a horn to any size
and dimension to satisfy your needs.

Will the tweeter have good dispersion? I don't know. Just like building the Imperials,
I didn't know what I was getting into until I turned them on.   Maybe the horn
tweeter will have the same effect. (Do they have an exploding head smiley, ala
the Scanners shot  ;)

Cheers

Gaz