I have a theory about horn flare rates, based on my own experimentation: A gradual horn flare tends to rely more on horn loading, while a dramatic horn flare like my early Crusher designs used takes more advantage of quarter-wave resonances. I am going to try to strike a balance between these two, to use a resonant peak at 45 Hz to strengthen the low end output of the crusher a little bit, but I think I remember hearing the quarter-wave resonance is less damped than the horn loading, so I don't want to overdo it or else it will be like a big Bose wave cannon, capable of "drone" or one-note bass but not much else. When you take a look at the tuba, I think it has a very dramatic horn flare, so as a result there is a lot of quarter wave resonances affecting things.