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

@jeffvegas , I will do it for you. One way, 8 foot ESLs are King.

As I said earlier in this thread, I have compared 2 speakers, one set time aligned, the other set, not.

They are Jeff Bagby's DIY kits, the "Kairos" speakers, and his "Adelphos". Same drivers (the great SB Acoustics 'Sartori' ring radiator tweeter and 6' MID), same size enclosures. The Kairos are aligned, the Adelphos were designed for those who don't want to tackle building an angled enclosure. 

As good as the Adelphos are, the Kairos created a bigger soundstage and more precise image. 

@mijostyn I would like to be a Buddhist, but that is about as far as I got. But I do know enough to know that snarkiness is not a positive attribute.

I am pretty sure that the phase is usually more critical with bass than timing.

Our ears and brains are good at getting the direct path, and depending on the speakers directivity and echoyness of the walls, then reflections usually affect the frequency response.
The more delayed echos, can add some ambiance.

I agree it gets complicated in a room.

@holmz , phase and time are attached at the elbows. It is certain easy hear what happens to imaging if you compare the two channels 180 degrees out of phase. The smaller the phase angle the harder it is to hear. Time, when you are talking about a few milliseconds or less with subwoofers is audible if you cross where I do up at 100 Hz. Lower down it is something you feel. As time variation increases the transient response of the bass has the edge taken off and you do not feel the impact as abruptly. Go to a small jazz club.  Listen and feel the bass drum. That is what you are shooting for. Time aligning subwoofers empirically is a real PITA. With a measurement mic you can do easily and know that you have it right on. The advantage of DSP here is that you can keep the subs where they perform best and align but delaying the signal of which ever speakers are early. 

As for room acoustics I have come the realization that too much absorption is better than too little. The acoustics of the venue are either in the recording or are being created with echo. There are not many instances where we listen to music in small rooms. You really want to minimize all early reflections but in a small room they are all early until they bounce around several times. Speakers that have sharp dispersion limits such as horns, planar speakers and linear arrays have large advantages acoustically in residential rooms. A properly deadened  small room say 16 X 30 sounds better than a really big room with high ceilings because these rooms usually have acoustic signatures that are harder to get rid of, they echo.

Reflections certainly change frequency response which can be easily seen with a measurement mic. But, they also smear detail and ruin the image.

@mijostyn lets say we have two wide band speakers.
And we time align them in the 10-20kHz region.

One has a 12dB/octave HPF slope at 2.5 kHz.
The other has a 24 dB/octave slope also at 2.5 kHz.

The phase between those two will look different in the DC to ~5kHz region.

Then lets say we have time aligned a woofer and sub at 120 Hz.
The sub is in a bandpass box, and the woofer in a sealed.
as the frequency goes towards DC the two will deviate in phase from each other.

We could address both of the phase in the first case, and the group delay in the second case with a DSP to correct the phase, or at least in the tweeter case, some XO magic can be done to better align them in phase in the ~2.5 kHz region. (I cannot do it in solder, but many can).

Usually the time alignment is done, in a “minimum phase” sense… and it is done somewhere where the phase is not swinging wildly from say, group delay.

So they are tied at the elbow, but they’re distinctly different once we talk about more than a single frequency. At any given frequency they are effectively able to give the same correction.