Time coherence - how important and what speakers?

Just because a speaker system has a sloping baffle does not mean it is time aligned. There are a few manufacturers who would like for you to think there speakers are time aligned. This has been noted in Stereophile's reviews of speakers from time to time. Also, there is the phase issue which can undue the alignment regardless of the physical alignment of the drivers. Take a look at the impulse response of speakers and it gives you a pretty good picture. Sometimes the midrange is wired out of phase to the tweeter or woofer(pick your order)This effects when the sounds arrive. I have said in many posts that accuracy is not that big of an issue it seems. Electrostatic speakers have a terrible frequency response in general. Just look at some test results. But people like them. Don't take my word, look up the test results. They also have issues similiar to what was mentioned in a post above in regards to a 6db filter requiring a broader overlap of frequencies for its drivers except the electrostatic is trying to make a diaphragm work at most frequencies equally well which it won't.
We ALL like our colorations. Pick your poison. It appears that no design has a market edge on another. Each design has its camp. However, I personally believe in time and phase coherent speakers. If you have a speaker that produces overtones that are out of phase and not arriving at the same time as the fundamentals of the sound---they call that distortion---it distorts the original waveform. I still ask the question, who has heard perfection to know what a sound should be on any speaker unless you were in the studio for the original. Even then, most of the recorded music is mixed down and altered until it is some small piece of what it started out to be.
Hell, you've got a bunch of people who like Bose cubes with a sub. Who am I to say there wrong? Man, this argument will go on until the end of time. To phase or not to phase---to time align or not time align.
Richard Hardesty has his views that have developed over many years of listening along with most people who believe in time aligned, phase perfect speakers. Technically, there is a strong argument for this. It takes a lot more to design these speakers. More is put into the drivers for the very reason mentioned above. Compare Vandersteen's frequency response curve (or any other spec for that matter) with any speaker you want and they will hold their ground easily. Any time aligned and phase perfect speaker specs out very, very well.
My bottom line here is specs and design must not be the only issue for us audiophiles chasing our tails!

Sure time and phase coherence are important, but these are only two aspects of many that go into how a speaker sounds. If a manufacturer achieves time/phase coherence but botches the crossover or driver integration, cabinet, etc. the result will not be pleasing. Gotta look(& listen) at the whole package, cause that's what you're ultimately hearing. I definitely hear something a little different when listening to Thiel speakers in terms of image specificity and a sense of dimension, but I don't know how much of that is due to their time/phase coherent design. Along with those mentioned above, Meadowlark is another company the adheres strongly to this design philosophy and much can be read about it on their website.

http://sound.westhost.com/ptd.htm

"Do think this is an important issue?"
Its certainly something to strive for and can be easily attained. However, when price becomes a factor it may not be something one should get hung up on- as there are other things to the speakers performance that are also important. Ozfly says it right in the next to last sentence of the second paragraph.

"What speakers are time coherent?"
Any speaker with a sloped or staggerd baffle has the voice coils (acoustic centers) of the drivers lined up and this is time-aligned, a starting point (assuming the xover also keeps the drivers in phase--fortunately they usually don't go through the trouble of staggering their baffles and then ignoring the xover). Full-range loudspeakers are also time-aligned by default. And to a lesser extent in population, systems with the tweeter below the mid/woof but still on the same plane are also physically time-aligned. Thiel, Wilson, Dunlavy, Biro Technology, Spica, Vandersteen, Avalon acoustics (pretty sure), Audio Physic, Lowther, Full-range Electrostats, Martin-Logan above the bass driver (not sure what they do w/ xovers), Vienna acoustics (pretty sure) etc. to name a few off hand. Drivers can still be time-delayed electronically too, so the speaker may look conventional but still compensate for it.

Bound for Sound just wrote a piece on this in their new issue. Per the editor, Martin DeWulf, there are only three elements to sound (phase, frequency and amplitude) and time coherence is smack dab in the middle of the phase element. Low order cross-overs, preferably of the series type, now seem to be the preferred (but not sole criteria) speaker type for Mr. DeWulf. I've owned a couple of Thiel models and have to say that, to my ears, time coherence makes music palpably real.

On the other hand, that does not mean that other designs can't work. They just need to compensate, IMO, by doing other things incredibly well. Plus, first order cross-overs may lead to potential issues with being able to drive speakers within their optimal parameters. For example, first order cross-overs allow more of the midrange to leak into the bass speaker and more of the bass to leak into the midrange speaker. This could lead to a muddying effect (e.g., the doppler effect when the bass speaker is moving in one direction with deep base waves and the smaller midrange waves reproduced on that same surface are either accelerated or decelerated as a result). All in, no single criteria can be the deciding factor since every design decision is one of making trade-offs. Let your ears decide.

I'm very happy with my PBN Montana KAS speakers and must confess that I have no idea what cross-over design is being used. I do know that some time coherence is being considered in the design since the speakers are at different distances from the vertical plane.

There are a couple of other brands too - Thiel, for one. I don't have a particular opinion on it, other than that I recently compared Vandersteens and MartinLogans, and for my tastes, it wasn't much of a contest. Whether that is because time alignment means nothign to me, or because other things about the Vandersteens were not to my liking, I can't really say.

I would have thought that the time alignment would mean better imaging, but for the music I played, that did not pan out.

Richard Hardestry (spelling?) is adamant that no speaker is worth diddly without being time aligned. I've paraphrased a little, but there are so many wonderful speakers out there that aren't (or at least do not claim to be) that one has to think that he's overstated his case ... just a bit.