Does Time alignment and Phase coherency make for a better loudspeaker?

Jason excellent point which is why i don't use or advocate modern multi track recordings as a reference. Cat will chase own tail using those......

2 or 3 microphones please....

All the rage back in the early 80s. Until everyone discovered that it was marketing nonsense.

I only noticed time alignment issues with present highly modded Klipschorns when in stock form. Originally mid driver and tweeter mounted on same baffle, mid driver sat probably 17" behind tweeter, this due to long exponential horn on mids. My mods replaced stock horn with Volti tractrix and tweeter mounted on separate baffle. I've mounted tweeter baffle essentially in line with mid driver. In stock form Klipschorns and some other Klipsch perceived as bright, certainly true with mine in stock form. Better time alignment has meant better tonal balance, no more of that beaming high and mid high freq., also far superior imaging, sound staging. But then, this was extreme example of poor time alignment.

My Merlin VSM-MM never had perceptual time alignment issues. Having said that, I did run Omega single drivers  with 2a3 at one time, coherence was really something special, even compared to Merlins, a two way which have rep as  being very coherent.

As for phase, I recall seeing a website some years ago where someone measured and listed cd's recorded in proper and reversed phase, turned out recordings pretty random here, reason for phase switches on many dacs.

Professional speaker management systems at the top of the scale in performance all have adjustments for time alignment. When you start talking about several stacks of drivers it starts getting a bit more complicated. There is a masters level course in the subject at one ot the TX universities, professor wrote a text on the subject. I got the books somewhere can not remember the professors name.

If you setup a speaker system in a anechoic chamber you can definitely hear the change with changes in timing if you are sensitive to the issue. The crossover points seem to be noticed by most people even in the a good listening room. To me it just sounds noisy at the crossover points.

I am working out a design for amps and such a management system on a budget. If interested check out "mini DSP", they have off the shelf solutions that are not too expensive. The DSP chips they use would be a good place to start a study of the issue, easy to work with.

I like the idea that the system could be used to make a system with a series of appropriately placed divers and apply a spread spectrum digitization of someone talking and aim the system at particular person in a crowd and that person would be the only person that would hear the person talking everyone else will only hear noise. Nice toy for spies. There is a patent on such a system.

So yes, it makes a difference.

It can but speaker designers who use computer models are getting very close.  That being said and owning Vandersteen 5As, just because these speakers are does not mean that they always sound fantastic.  There is more to making a system sound fantastic then the speaker.

Happy Listening.