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

Ahh, John Dunlavy. What an amazing speaker designer. RIP.  loved selling his SC IV's and V's back in the day. One of the best loudspeakers I've ever heard.

I have a pair of Thiel CS6 speakers for which time and phase coherence were prime design considerations. This was Jim Thiel's raison d' etre. The CS6 even had the tweeter in the center of the midrange cone to maximize the coherence of the speaker.

As for sound, I went to the 2018 AXPONA and was pleasantly surprised that my speakers and system holds up to pretty much anything I heard that cost less than 6 figures. I think my speakers sound very good for a variety of design reasons but the time and phase coherence have a significant effect.

As mentioned in previous posts there is a tradeoff for any design philosophy and in the case of Thiel speakers it was the need for high current amplification. My speakers have low sensitivity combined with a brutal impedance curve. I run them with a Krell KSA 300S amp that will put out 2400 watts @ 1 ohm and weighs 185 lbs. If you like tube amps you are pretty much SOL.

I've heard lots of good sounding speakers that didn't have time and phase coherency as a primary design goal but I think this characteristic improves imaging to some degree. The imaging in my system is almost scary. On some recordings I feel like I can reach out and touch the singer or particular instruments and the depth of the image is holographic.

Every speaker manufacturer has their "thing" that defines their unique selling proposition. For Thiel (and Vandersteen) time and phase coherency is their marketing hook but in both cases their designers combined a range of good practices to make their speakers sound great.

I agree with 8th-note.  I have the Thiel CS6 speakers too.   On some recordings I feel like I could get the singer's autograph.  The top Vandersteens are the only other speaker I have heard that does that and sounds a bit better.  All it takes is money.

I suspect Mr Vegas is a reincarnation of another fellow we all 

know and miss. Not.

I well-remember the magic of listening to Dunlavy's in Colorado Springs years ago in The Sound Shop, at a friend's home with IVs, and listening with John Dunlavy and meeting him (a wild guy) in his CS facility. They were very special but a tiny magic zone. For generally superb musical quality but one-person listening, they might get on my list.

As for knowing if I can really hear time and phase coherency, I'm not real sure of my ears unless someone told me what to listen for. I might be able to with a bit of learning.

I do know I am very sensitive to frequency adjustments and much prefer the sound of a room that is bass-corrected and very minimally DSP processed to yield a flat frquency curve with care to time and frequency. A 'repaired' room always sounds cleaner and better defined with no loss of bass intended to be there originally.