Time coherence - how important and what speakers?

I don't have the means or ability to test my listening impressions. With that said, I have found the sweet spot of low impedance speakers to be wider in the horizontal plane and narrower in the veritcal plane. Despite the fact that my mother used to teach ballet, I'm not prone to dancing. I usually listen alone. As such it's an easy compromise to live with. Interestingly, the Dunlavy's seem to have overcome a bit of this vertical sweet spot compromise.

Jeff, The last statement you made about "truer" sound is where the problem lies. What is truer? Is it based on measurements or are you ears "truer" than mine (which could be the case considering the age factor!) My point was that to each individual,truer takes on a different opinion. No speaker is perfect, as I said, and therefore is not truer unless you use a subjective analysis(as in your case---your ears.)
I actually talked to Richard Vandersteen at some length about his design and, like you, he could not listen to anything but a "slow slope.")Is he wrong in his opinion? To his ears, it was "Truer." He also believes in the "Baffleless" design. I definitely feel that speakers with a large area surrounding the tweeter and midrange affects the sound negatively.
I have listened to your speakers extensively. I do know set up affects them and they do have a sweet spot. I also find them somewhat analytical with a slightly dry sound. I hate to say this but they sound somewhat similiar to the B&W Nautilus line(which I owned for a while--805's and 802's)which i feel ARE excellent speakers but not for me.
I'm certainly not going to tell you your design is wrong and that your speakers don't sound correct to you. I'm sure your speakers are well built and deserving of the interest they get. However, I am going to tell you they do not sound truer to me for whatever reason. I find the Vandersteen to be as dynamic and accurate as sounding as any speaker system I have owned. They may truly be +- 10db off axis but they sound damn good on axis where I listen.

First off, the participation of Jeff Joseph and Roy Johnson have made this thread among the best I've ever encountered here.

Like the guy said to Einstien after one of his classes, "Before I heard your lecture, I was confused. Having heard your lecture I'm still confused, but on a much higher level."

I thank you both, Roy and Jeff, for taking the time to educate us. I hope you will feel welcome here whenever you see something that calls for your participation.

From the body of evidence presented, one might conclude that the ideal would be a single-driver full range loudspeaker whose radiation pattern remains uniform up and down the frequency range. Just so happens this has already been done. Sound Lab's big full-range electrostats have the innate coherence of a single driver, and their unique (and brilliant) faceted-curved geometry maintains coverage over a 90 degree angle front & back, from the dipole-pattern bass all the way up through the high treble. Of course the Sound Labs have compromises of their own (low efficiency, high cost, somewhat limited maximum SPL, large size, and demanding room placement). But to the best of my knowledge they are the only truly full-range loudspeaker to incorporate the otherwise mutually exclusive properties of time/phase coherence and uniform radiation pattern. Non-coincident multi-driver systems can't do both; there are no coincident (concentric tweet systems) that use first order crossovers; and "full-range?" moving coil driver speakers (like Lowthers) aren't truly full range. And besides, the radiation patterns of all these cone drivers change significantly over their operating range.

I suppose a concentric-tweeter driver with a first order crossover and a cardioid radiation characteristic in the lower octaves could also achieve both time/phase coherence and uniform radiation with respect to frequency. But I don't think that's been done yet.

Disclaimer - in case anybody doesn't know or hasn't figured it out, I'm a Sound Lab dealer.

Audiokinesis - Unless I misunderstood your post, Thiel incorporates the tweeter inside the midrange in a concentric design in its 2.3 speakers (and maybe others) and I believe they also use a first order crossover -- so the design does exist. The woofer is a seperate entity though.

Soix -

Thanks for pointing out my oversight! I stand corrected.

Theil actually has at least two concentric drivers, one of which is a mid/tweet module (requiring a separate woofer), and one of which is a midwoof/tweet module, requiring no separate woofer.

The radiation pattern would still vary considerably with respect to frequency, but output from the concentric units would be free of the off-axis anomalies that otherwise occur with non-coincident drivers using first-order crossovers.