I'm not sure whether a dome, cone, or circular flat-panel driver, will have significantly different off-axis dispersion patterns. Does anyone have any sort of measurements and/or simulations that might shed some light on this particular characteristic?
It's a little annoying that two different topics are about the basically same subject.
Yes, the directivity of a dome is different than from a cone speaker.
This has been discussed in the two books I keep on bringing up by Eargle and Borwick.
Typically in a 3-way system, the directivity is very low, so a much wider dispersion.
As for why and how there is a lack of midrange domes;
I am basically gonna repeat what I said in the other topic about cone tweeters.
In this case midrange domes only full-full a small niche.
They made a lot of sense in the 70s/80s, when most tweeters couldn't be used below 2,5-3kHz as well as in combination with a 10-12 inch woofer.
These days the majority of tweeters, even without a waveguide, have no issue at crossing around 2kHz.
Also 5 inch mid-woofers perform an awful lot better. (since distortion always seems THE selling point no matter what)
While the crossover is much more simple and cheaper, compared to a 3-way system