Is there measurement that correlates with cohesive/pinpoint imaging?


I am currently using single-driver Omega alnico speakers which have the most coherent imagining that I've ever heard.  However, if I wanted to compare them with other speakers (including multi-way speakers with crossovers) in that regard, are there any specific measurements to account for?  Would measured delay between driver signals in a multi-way speaker be a useful proxy?
redwoodaudio
AFAIK, there is no 1 number for this, but if you want to jump into a fun rabbit hole, research "Head Related Transfer Functions" or HTRF for short. :)
Is there a measurement that correlates with sound stage depth? Width? Timbre? Palpable presence? Slam, punch, drive, grain, glare, detail? Is there a speaker measurement that actually does correlate with anything that matters? Yes: sensitivity. 

Does it tell you anything about how the speaker sounds? Not really. But at least it does give some idea how much power you will need. Which is more than can be said for any of the other measurements. 

Its the only measurement I paid any attention to when buying any of mine.
Well, that's unfortunate!  Lots of speaker companies claim to have a focus on coherent imaging, but nobody has any idea how to measure it?  Do phase alignment/time alignment correlate?
Lots of speaker companies claim to have a focus on coherent imaging, but nobody has any idea how to measure it?
it is measured by frequency response tests
Hey OP:

You really should at least start to read about HRTF. It will help you see the problem of imaging in a whole new light, and why it is so hard to measure.


  Do phase alignment/time alignment correlate?


Not in my experience, but clearly the fans of speaker brands like Thiel and Vandersteen feel strongly they offer special features you cannot achieve otherwise.  Personally I vote with the literature, that says we aren't that sensitive to phase or time alignment. We _are_ sensitive to badly matched drivers however.

There's also some research saying that making the frequency response dip around 2.4 kHz enhances the experience with the trad off being a neutral frequency response.

It is also important to include the room in these discussions. Not only does controlling reflections matter but enhancing diffusion in areas also helps a great deal.  I find that imaging is enhanced in the same plane as the room treatment.  Want wider?  Treat the sides.  Want taller?  Treat the ceiling.  Want depth? Treat behind the speaker and behind the listener.

The best speaker in the world can be ruined by a poor room.  Conversely, some speakers reduce the interaction with the room, like line sources, planars, horns and open baffle.



Time and Phase. Study how the highly evolved ear brain function to localize food and threat sounds and you will understand it is small timing differences. Add in low diffraction because a large baffle destroys time information while functioning as a mechanical averaging machine ( frequency response )
read what JA has to say about Vandersteen “imaging champs”.... 
I will say if your references are studio multi track efforts you might be leaving a bit on the table relative to expectations, especially image depth

enjoy your speakers ! And the music
because a large baffle destroys time information while functioning as a mechanical averaging machine

Wait, what? Some of the best sounding, best imaging speakers I've ever heard are the Sonus Faber Stradivari and Snell A/IIIs. 

You can make a wide baffle with low diffraction, and if you can go for it. :)

Best,

E
Look at active speakers using DSP like Kii and Dutch and Dutch as well as studio monitors. 
I had a pair of Snell back in the day.... and Thiel, ESL63, Vandersteen..... I still have them, except....for the Snell. I certainly recognize the genius of Peter and they were quite good....

a curved baffle helps but I don’t think it’s SOTA any more....


I'm afraid all the components in the Snell A/III are outclasssed today, but for imaging and impact, amazing.  The SF Stradivari are much newer and deal with the diffraction issue very differently than a large box does.  Outstanding.
of course

measurements and specs explain everything, what is the matter with you?

in fact, they mean so much, are so meaningful and all encompassing, that i think will soon give up listening to music altogether and just log in and read ASR

i will have the specs and measurements on everything having to do with hifi, won’t even need music anymore

you’ll need to excuse me now, its late and i need to cuddle in bed with my oscilloscope


Above... That was a helpful addition to the thread. Thanks! 

Otherwise, how are these multi-driver speakers solving this problem?  If there's engineering involved there's got to be some math or measurements of some kind.

Do any speakers truly image as coherently as single drivers? If so, there must be a theory. 
I just told you the answer 
Single drivers do not really image coherently. IM distortion from moving at largely different frequencies ruins perceived cohesiveness, not to mention different parts of the speaker behaving different at different frequencies.


Imaging in most recordings is purely conceptual. It is manufactured. Most live recordings have nothing remotely like imaging either with very odd exception and even then. That makes left-right manufactured, and depth to pretty much. Height? It is not there. It just is not in the recording.

Audiophiles will convince themselves of a million reasons why "imaging" is better or worse, right down to fuses. It makes me laugh. Imaging is almost exclusively your room and your speaker and of course the recording. Really awful electronic can impact imaging, but we are talking last bit, and most people are not remotely there.


Want pinpoint imaging .... go into an anechoic chamber or wear heaphones. I know, not the answer you were looking for. Headphones are better, but an anechoic chamber can be a good substitute. Sound a bit like crap though.

So, can you measure imaging? No, but you can measure that impact of the speakers, room and electronics on what reaches the ears and get a relatively good impression of what the likely imaging is like. What I can’t tell you is whether you will like it. It is a trade-off between imaging and ambience in the real world with speakers.
@tomic601 
Time and Phase....read what JA has to say about Vandersteen “imaging champs”....

Thanks for the helpful reply.  I just read JA's review of the Vandersteen Quatro Wood.  His measurements are interesting.   https://www.stereophile.com/content/vandersteen-quatro-wood-ct-loudspeaker-m5-hpa-monoblock-power-amplifier-loudspeaker

"Fig.5 shows the Vandersteen Quatro Wood CT's horizontal radiation pattern, normalized to the tweeter-axis response and plotted up to 45° to the speaker's sides rather than the usual 90°... The contour lines in this graph are impressively even, implying stable stereo imaging."   

"Like its predecessors, Vandersteen's Quatro Wood CT offers a true time-coincident output, due to the stepped-back sub-baffles for the upper-frequency drivers, the first-order crossover slopes, and the fact that all its drive-units are connected in positive acoustic polarity. Fig.9 shows the speaker's step response on the tweeter axis. The initial arrival is an almost textbook right-triangle shape, though the tweeter's output arrives slightly before that of the midrange unit. This confirms that the optimal axis will be 5° below the tweeter axis. Finally, the Quatro Wood CT's cumulative spectral-decay plot (fig.10) is impressively clean."

  

I do know that in the same room with the same equipment, my Omega single driver speakers had a much more coherent and precise image than my Klipsch Forte IIIs and a pair of Vienna Acoustics Mozarts that I compared a little.
@djones51   Thanks for the tips about these other speakers
I have the Dutch and Dutch 8c, I never really listened to single drivers at least since the 1970's when I didn't know that's what I had. The D& D are very coherent I guess because they do the crossover in DSP. 
And the really excellent designers use science and listening and a deep love of music to move the art forward- stereo is an illusion after all. There are some excellent recordings utilizing research and products coming out of work on head transfer function - Macy Gray and Amber Rubarth come to mind - both excellent and hyper frustrating at same time. I will post LP numbers if desired....


The problem with attempting to use head transfer functions at the recording level is it requires near perfect playback setup (specific to the recording unless you are using headphones), and not something readily or even achievable in most people's playback setups. Until we substantially change the listening system away from 2 channel speakers, we are pretty stuck with that is possible though advanced DSP algorithms and controlled reflections has promise in advancing what is possible with 2 channel. Sorry, analog just is not going to cut it for those advancements.
It’s funny how how people like djones and others accept that something exists without measurements to prove it when it suits them. Yet when it comes to cables, etc, they use the lack of measurements as proof that cables don’t matter. Same thing with gene at  audioholics. Always talking no measurements for cables to prove anything, yet anytime I ask him about showing measurements for imaging, timbre, etc, he goes silent and disappears. 

I have measurements in REW which shows a nice smooth curve over frequency from 20 hz to 20khz. If the speakers lacked coherence it would show at the crossover points. They were really pretty good before the filters but they did help especially below 200hz. I don’t recall saying something didn’t exist without measurements. I think it was more measurements show it isn’t audible. I don't know if measurements can show timbre I believe there would need to be a blind listening test to see which speakers reproduced the sound of a violin or saxophone more realistic.
IME, speakers with good measured step and square wave responses tend to image well.
Within a frame work of two channel audio, it is not simply timing information that is important, but relative timing information, i.e. the time difference between arrival at both your ears. To that end, a large baffle will not impact the primary wave front timing differential between a signal from one speaker to both your ears. Maybe you meant something else?


Time and Phase. Study how the highly evolved ear brain function to localize food and threat sounds and you will understand it is small timing differences. Add in low diffraction because a large baffle destroys time information while functioning as a mechanical averaging machine ( frequency response )

There are predictors of great imaging. The first is avoidance of cross overs and phase aberrations. The second is that both sides have identical frequency  response curves. This one is tough, No two speakers are exactly alike but then you put them in different positions in the room. Maybe there is a window on one side only or whatever. The point is that each speaker has a unique acoustic environment. This is why symmetry is so important.
The best results are always going to be with a "one way" and full spectrum room control. With the best units you measure each speaker with a calibrated microphone then correct the speakers response so that they are dead flat. Then you can make adjustments as you like. The best unit out there now is the Trinnov. Anthem and DEQX make decent units.
Many "audiophiles" downplay the use of these devices feeling that they are just like tone controls and equalizers, detrimental to the sound. They are not. They are digital and process at very high speeds, at high bit depths. There is no distortion, phase or otherwise.
Perfect frequency response from both sides sounds like it would be super important but in practicality for what most people describe as imaging it is not. Symmetrical installation in general is far more important.


What most people describe as imaging is not exact placement, which has no meaning at all really. If I have a left / right volume difference and something shifts 6" to the left or right, that is not going to be critical.


What most describe as imaging is an ability to visualize an exact spot for the sound source, not just "over there" though a lot of people like "over there". A well designed cross-over is going to provide, given suitable speaker/listener distance time coincident wavefront and certainly with digital cross-overs, it is very easy.
Certainly you are familiar with the two slit experiment, just model a mid and a tweeter on a large baffle and let it rip for a few cycles.

as for precision matching of drivers and pairs, that is a hallmark of Vandersteen for 20 plus some years now, I know they all go in the chamber for a filter tweak as well - the 7 are matched to .1 db as I recall
- the matched pair are delivered with the actual plots. Obviously an unsymmetrical room can present challenges, as Eric suggests some treatments might be appropriate and of course there are fans of DSP.
Of course this fanboy has other speakers that have positives as well: Quad ESL 63, Thiel 2.3+, Dynaco A-25, some Totems.... some tiny baffle Sonus Faber that throw a super big 2D image ....

rather than focus on hyper flat frequency response maybe measure the RT-60 of your room.....

measure and listen but always enjoy
Whenever a question arises, regarding sound stage and imaging; I make this suggestion: The following provide tests, with which one may determine whether their system actually images, or reproduces a sound stage, as recorded.      ie: The LEDR test tells what to expect, if your system performs well, before each segment.      On the Chesky sampler/test CD; David explains in detail, his position on the stage and distance from the mics, as he strikes a tambourine(Depth Test).      The Chesky CD contains a number of tests, in addition to the LEDR.    (https://www.audiocheck.net/audiotests_ledr.php )      and: (https://www.discogs.com/sell/release/2818064?ev=rb)      An article, in Stereophile, on the subject: (https://www.stereophile.com/features/772/index.html)      The LEDR eliminates the variables, far as what's on your source material (recording/miking methods, etc), when doing listening tests, in your room.
I'll vote with eric on this issue....
One can have outstanding equipment that still sounds like dreck.
Conversely, 'meh' can shine, given a sensitive set-up in the 'well-tempered' room....

Why? One asks..  HRTF in our 'real world'.
It IS what you hear, and most times, Where you are when listening to it.

I'm not a huge fan of the 'rooted to the floor' chair 'sweet spot'.
Generally, when @ a venue, hall, or an outdoor concert, having the 'best spot' to enjoy becomes a function of having the $ for the seats or the timing to place one's tush there.  So most times one gets to listen where one is...
In ones' home, set-up of the listening 'volume' becomes (imho) just another parameter of the items within it.
First reflections, room volume vs. base freq. and it's harmonics, 'live' vs. 'dead', eq or not to eq, spl low or high....on and anon....

Unless you were raised with your head in a foam ball and have 'virgin ears', unsullied by the wear 'n woe of uncivilization, it's a near given that your ears are not Perfect.

Therefore:  Your perception is Flawed.  So is Mine.  No 2 of us 'hear' exactly alike....unless your share a head with another body, and are pretty much on y'all's own.

If one must have the perfect listening experience, free from all of the variables noted above (which isn't complete...oh, no....)...

Buy the Best Isolation Headphones one might aspire to.
...and give it a break....

'Cheers', J