The quest for ATH generated (R-OSSE) free standing round/octagonal MEH

[ImpuPerf]

Pretty sure that the secondary flare will be an improvement, as suggested by Keele. Everything You do to get rid of reflections will be good, with the exception of the wanted 1/4wL notch between port and CD(should be just above xover freq according to Danley). Less reflections means less ragged horn loading, response and less distortion, I believe a curved mouth will do best(e.g. tractrix, kugelwellen, OSSE, LeCleach, exponential). A Swedish study suggest the expansion rate should increase fast in the last section of the mouth, so it seems easier to adapt the OSSE-function for this. Simulating in Hornresp suggests that the port lenght can be as much as half the notch distance which would simplify driver placement, but, as always, You get nothing for nothing, that may introduce resonances in the port...and I doubt there is a way to dampen the port with airspeeds close to 17m/s. Anyway, mouth size should be as big as possible 🙂