If a front tractix or exponential horn has say, a 250 hz flare, does this mean everything below that point is inaudible? or wd it have a steady acoustic roll off meaning i cd use a simple filter for my driver and hook to a sub perhaps?
In practice the horn+driver often have a sharper roll-off than that. 5th order is common.
And H2-H3 distortion will rise sharply before you get to that nominal cut-off frequency, thus staying an octave above it is good practice.