this is further on the earlier talks below. i thought to put it here so it would not be lost to see.

i want to compare horns to hear the difference of diffraction in the throat makes. one has straight walls with the compression driver at the tip. the other has straight walls after the rounded part at the beginning. the rounded part makes there be not an edge at the transition point. so far so good.

my trouble is to realize the slits in the phase plug cause diffraction too. even if the slits are rounded and smooth they still make an abrupt change from dome to compression chamber to phase plug slits to throat.

that made me to think: is there any way to make a compression driver that doesn't have diffraction?