Time coherence - how important and what speakers?

Unsound---they lied! It HAS to be a first order filter period. The phase shift created by a 24 db slope would be tuff to fix. Read Richard Hardesty's issue #3 of the Audioperfectionist. You might not like his recommendations but his science is correct.

This topic comes up every few months. Designing for phase coherence may be intellectually gratifying, but here are my questions for the Phase Coherence Uber Alles crowd.

1. What does time coherence actually sound like? How could you tell a time coherent design from a non-coherent one without
looking at the measurements? Why does almost every online list of "coherent" models include some that are not?

2. If all time coherent speakers are correct, then why do they sound so different from one another?

3. If this characteristic is so important, then why do only a few companies embrace it? and why aren't those companies dominating the marketplace?

4. What about OTHER factors such as distortion, wave interference, off-axis lobing, compression etc.!? Wouldn't these have much more influence over the quality of sound?

5. If this approach is the One True Way to superior sound, then why do people vote us Best Sound At Show?

Josephaud, to answer your questions:
(1). Time and phase coherent speakers sound as though they are "cut from one cloth" with less noticible diferrentiating sound of different drivers and cross-overs. They consistently demostrate superior sound staging and imaging.
(2). Because they uses different drivers, boxes etc. Would you ask the same question of different manufactures that share similar design priorities e.g. Acustat or Audiostatic?
(3). Perhaps it takes more talent, effort and expense in design equipment.
(4). Perhaps? Perhaps not?
(5). With all due respect not all people vote you Best Sound at Show. You have never been in the running when I vote.

I'll take a stab at Joseph Audio's post: First of all, no one ever claimed that time and phase coherence is the only important parameter in loudspeaker design (at least, no one with any sense). There are many, many factors, all of which are extremely important, and any one of which, if ignored, will detract in a significant way from the end result. THAT is the crux of the matter.

So how do you know that time and phase coherence is critical? So few speakers have these characteristics that many people are fully acclimated to the sound of noncoherent designs, and so will not notice that anything is wrong. All the individual "sounds" are there, and in the right volume proportion, and they all have excellent attack and decay, etc., but the speaker itself does not sound "coherent". I hate to use such a nebulous term, but it truly sounds as though there is not a musical whole, but rather a bunch of separate musical events occurring more or less simultaneously. It is the difference between "natural", which allows you to relax into the music, and "a really great stereo system", which may be fantastically impressive at a hifi show but never actually fools your brain into thinking that you are listening to the real thing. That is my personal opinion, but it is nonetheless exactly what I hear. When it is right, you simply forget that you are listening to speakers. And it occurs with vastly disparate design philosophies, including multiway cone/dome systems, electrostatics, and Walsh systems. Although they are instantly distinguishable from one another due to their vastly different dispersion characteristics, all of them allow your brain to relax and feel as though you are listening to real music. I have never heard a noncoherent system that could do this, not one, in over twenty years of being obsessed with hifi and music. Sure, I've heard plenty that sounded like great hi-fi speakers, but that's an entirely different subject.

That, in a nutshell, is my personal answer. Do not presume that I or others are just making this stuff up for our own intellectual masturbation. It is very real to us, every bit as real as the anechoic-frequency-response or cumulative-spectral-decay graph is to you. And every bit as important, even if it is only one of many things that are every bit as important.

In response:

Unsound: Please allow me to expand on your comments one by one:

1. I've heard this said before regarding imaging and soundstaging. But I must tell you that as I've examined different topologies, I've found that other things such as
the dispersion characteristics, smoothness of power response, and clean decay corellate more powerfully with imaging and driver integration. Indeed, our designs are almost always singled out for praise in these areas. A very steep cutoff has real advantages because the overlap between the drivers is better controlled, so you avoid the large dips and peaks in response that upset the smoothness of the power response in slow slope crossovers. If you allow the drivers to overlap over a broad range, they may add in phase at a single point in front of the system (and this can be a very very tiny point!) but they will have sharp nulls and peaks
at different points in space. This is why such systems have trouble in three dimensional space. These interdriver cancellations actually make the transition between drivers
easier to spot, at least in my experience.

2. Which leads to my larger point. There are SO many variables in loudspeaker design, from drivers to boxes to
crossover slopes to veneers . Change any of these, and the sound changes, (okay, maybe not the veneer.) Why harp on crossover design as the focal point? It's hopelessy myopic since as you admit, the speakers within the group are all different from one another.

3. Do you seriously believe that? I suppose Dr Floyd Toole, now at Harman International, formerly at Canada's NRC, must lack the resources or talent to create low order crossover based designs because his work corellates well with ours. You can read about the Harman intl facility in Stereophile, and other places.

4. Perhaps yes!

5. I didn't say everyone voted us Best Sound. You're entitled to vote for whatever system you truly loved.
However, more seasoned audiophiles voted for us at that show
than any other system.

Your belief in low order crossovers is just that. And once you've embraced a certain mode of thought, it's difficult to
consider a different one. There's a lack of supporting evidence as to the audibility of the small degree of delay associated with steep slope designs. In fact, the research seems to indicate that it needs to be 3 times the delay that exists in high order networks before it can be barely detected.
But once you believe that you can hear, it will tend to influence your opinion of whatever speakers you listen to.
And thus the belief itself can become the overiding factor in your assesment of a given system's sound.