Personally, my goal was to have a midrange horn that could crossover very low, so to cover the entire midrange band. The note C below middle C is 130Hz, so you can easily see that male voice has a lot energy in this range. Wavelengths are long at this frequency too, so spacing and overlap are not nearly as critical. I felt I could use a larger horn and crossover lower with a shallow first-order slope for a seamless transistion down low and keep all the vocals and midrange in one driver.

With a 1.6kHz upper crossover frequency, I didn't really need to reach very high with the midrange horn. That's where I spent most of my time, working on the aspects of the subsystem at this frequency. I am pleased with the transistion between mid and tweeter horns, truly the most critical part.

But anyway, I think it would also make sense to use a smaller midrange and push the crossover points up an octave or so. You could probably get a smaller 6" driver to go up to 3kHz, and maybe even further with a phase plug. That would then allow other choices for tweeters, so the idea certainly has merit in my opinion.