Time coherence - how important and what speakers?

Roy, that's okay to dominate the thread, I think we are all learning a lot. At least I am. One note though. Thiel speakers uses metal drivers and are first order (time coherent?).
Would a single driver be better still than 1st order crossover? I've got a 5" single driver speaker for a week. But it has a plastic "whizzer cone" glued on it. So I'm not sure if this counts as a true crossoverless design. Maybe mechanical, not electrical. Female vocals with acoustic instruments sound very different than my 4th order speakers. There seems to be more ambience to the music. But for some reason the single driver speakers don't have the pinpoint imaging.

ALso...Spica tc-50s were designed and marketed as a truly time and phase correct speaker...I know there is alot of jargon these days..."phase correct","phase coherent",etc...but the spicas...like Vandersteen, meadowlark,Thiel,etc...were the real deal...with that said...they were not a perfect creation...the highs were rolled off, they had very little bass, and were not very efficient...however...their 3-d imaging&spacious qualities as Roy mentioned were their claim to fame...and why they still fetch 3-$500 used almost 20yrs later...not much more than they retailed for back in the day...a great speaker during its heyday...and a fine value...but a bit outclassed today...especially in the detail department...at even at the $500 level...

Cdc- Thiels use a complex crossover circuit to force first-order acoustic rolloff responses from the drivers, because of their driver choices and cabinetry. Dunlavy and to some extent, Vandersteen employ similar approaches.

Your question about a single driver- if there was one with a perfect cone, free of breakup, the end result would be little bass response and very narrow dispersion in the highs. To widen dispersion in the highs and extend high-frequency response, a whizzer cone is attached, driven through a mechanical crossover (the adhesives used) between it, the voice coil, and the main cone. Those type of crossovers at best are 2nd-order, which means there's 1/2 wave-period of time delay at the crossover point. There are cone breakups usually still present. There are standing waves in the whizzer, reflected from its un-terminated outer rim. Those all are responsible for less than pinpoint imaging. At least their designers get to leave off any electrical crossover, which is a good thing, considering how much information is lost in most of circuits. Whizzer-cone drivers are not time coherent, but just less imperfect that most speakers that do use a crossover.

Phasecorrect- just remember that "phase correct" and "phase coherent" do not mean "time coherent". The converse does. See my first 02/12/03 post above.

Best,
Roy

I dont believe Vandy or THiel use "complex" x-over circuitry...these are afterall pioneering first order time and phase correct speaker designers...both Richard and Jim...and as RIchard V has openly stated...there are only a handful of truly time and phase correct speakers on the market...SPica would be the one that fall into a more complex x-over category...