The diffraction applet matched my intuitive concept of how the throat might work (just add horn walls), but I failed to consider that the horn mouth itself could act somewhat like a very large throat! I have a new perspective now.Could the vertical diffraction effect from a rectangular mouth (narrow height compared to lower cutoff) create obvious comb-filtering problems in a vertical line array of like horns? Would anyone really notice, even if they danced the "Pogo"?