I always liked this design option. If the.crossover point is low enough and the driver centers are close enough, comb filtering shouldn't be an issue. Always many variables in play, and pros and cons to each design choice.
The D'Appolito, MTM Configuration
One speaker technology which is I think old but hasn't gotten the praise it deserves is the Joseph D'Appolito configuration. In short, it uses a tweeter vertically sandwiched between two midwoofers. Using two actual midranges is a variation on the theme.
What got me thinking of this was the $220,000 speaker pair that appeared on Stereophile's coverage of the Florida Audio Expo, which made me think, fondly, of the original, 1980's era Focal Utopia where I first heard this arrangement.
It's a very good arrangement for those who love detail and want a speaker that's relatively easy to live with.
How about you? Have a pair of D'Appolito-like speakers ever won you over?