Given the fact that a horn has to terminate into open air at some point, I tend to surmise that there must be a LITTLE expansion beyond the boundary edge as the pressure is released, even within the horn's pass band. Is my hunch correct, or am I way off? If there's some meat on that bone, then my concern is that two tightly arrayed traps (covering the same frequency range) splayed at different angles might also create the phase-delay problem Dana mentioned. Someone standing on axis to one trap might get a delayed spillover from the other, resulting in time smear due to the differing path lengths to the listener. Any significance to this?

Yes, I've heard HF comb filtering in a large outdoor venue, where wide-coverage 2" horns were stacked next to each other horizontally. As I walked across the coverage area, it sounded like a wind storm as I heard the phase shift with every step. However, I did notice two things: One is, the farther I walked away from the stack, the less combing was noticeable (line array theory?). And two, when I stood in one place for long enough, my ear "adjusted" to the sound. The system was actively crossed and delayed, so I wasn't experiencing any multiple arrivals that I could detect. My conclusion: You can "get away" with a certain amount of comb filtering in certain frequency ranges if there aren't any other outstanding acoustic problems. I know, call me nuts!

However, the terminal flare rate is 38Hz, and in 1/8 (corner) space that means an overall mouth size of (approx.) 1160 sq. in. is required to prevent reflections and provide a smooth response.

It can be surmized that due to the nature of the confinement provided by the corner walls and floor, that the true horn mouth ocurs well outside of the enclosure (about one more expansion length) into the room. Since the Khorn is indeed capable of 38 Hz reasonably flat, there is something to be said about expansion outside the horn terminus.

Different mouth splay angles and horn terminus external boundary utilization techniques will have their effects and can be exploited somewhat to keep the size of the enclosure relatively smaller. Less of an effect can be achieved in 1/2 (stage) space placement, of course, being that only one boundary element is present, so it is not quite as "exploitable" as an environment with more boundary surfaces available.

DM