When the sound source eminates from the apex of a set of radiating planes that meet to form a trihedral triangle, then the DI of the source is 9dB. This condition can be made by a large stand-alone horn, rows of bricks or a room's corner that forms the boundaries. Consider the ceiling and the radiating pattern is constrained even more.

Seems like I recall you had mentioned one of your horns had a rectangular radiating pattern. One of the reasons I brought it up is that a 90x40 horn is useful for matching the condition formed by the room's boundaries when sound radiates from the corner.

Anyway, it's been great to chat with you and I hope you and Lidia have a very merry Christmas.