Bound for Sound just wrote a piece on this in their new issue. Per the editor, Martin DeWulf, there are only three elements to sound (phase, frequency and amplitude) and time coherence is smack dab in the middle of the phase element. Low order cross-overs, preferably of the series type, now seem to be the preferred (but not sole criteria) speaker type for Mr. DeWulf. I've owned a couple of Thiel models and have to say that, to my ears, time coherence makes music palpably real.
On the other hand, that does not mean that other designs can't work. They just need to compensate, IMO, by doing other things incredibly well. Plus, first order cross-overs may lead to potential issues with being able to drive speakers within their optimal parameters. For example, first order cross-overs allow more of the midrange to leak into the bass speaker and more of the bass to leak into the midrange speaker. This could lead to a muddying effect (e.g., the doppler effect when the bass speaker is moving in one direction with deep base waves and the smaller midrange waves reproduced on that same surface are either accelerated or decelerated as a result). All in, no single criteria can be the deciding factor since every design decision is one of making trade-offs. Let your ears decide.
I'm very happy with my PBN Montana KAS speakers and must confess that I have no idea what cross-over design is being used. I do know that some time coherence is being considered in the design since the speakers are at different distances from the vertical plane.
On the other hand, that does not mean that other designs can't work. They just need to compensate, IMO, by doing other things incredibly well. Plus, first order cross-overs may lead to potential issues with being able to drive speakers within their optimal parameters. For example, first order cross-overs allow more of the midrange to leak into the bass speaker and more of the bass to leak into the midrange speaker. This could lead to a muddying effect (e.g., the doppler effect when the bass speaker is moving in one direction with deep base waves and the smaller midrange waves reproduced on that same surface are either accelerated or decelerated as a result). All in, no single criteria can be the deciding factor since every design decision is one of making trade-offs. Let your ears decide.
I'm very happy with my PBN Montana KAS speakers and must confess that I have no idea what cross-over design is being used. I do know that some time coherence is being considered in the design since the speakers are at different distances from the vertical plane.