Time coherence - how important and what speakers?

NSM, Role Audio, and maybe Jordan single driver speakers are time and phase coherent.
NSM states "Time coherent" at their website here:
NSM

Any comments Roy?

Cdc, NSM is blowing smoke up your ... There is no way on heaven or earth that the speaker shown in your link is time coherent. As I posted early on in this thread, very few speakers are actually time coherent, and I've never ever seen one with drivers mounted to a flat vertical baffle that comes even close. Sure, many manufacturers would love to have you believe it, but one look at the step response is all you need to tell otherwise.

Roy, great summary of philosophy, which I agree with 100%.

Meadowlark has a simple and easy-to-visualize example of this on their website, www.meadowlarkaudio.com.

I've said straight out what I find wrong with the sound of higher-order crossovers and the philosophy of that sort of design approach, but have not critiqued the finer points of any design. That holds here, but I do appreciate Cdc's wanting to know more. I have commented on Audio Asylum about the Jordan approach, and can add no more here. I can say that at least NSM is implementing many good things! Karls is right though about the flat baffle, but not exactly because it is flat and also perpendicular to the floor.

Remember that any speaker design which permits cabinet reflections reduces much of its potential, including any attempt at time-coherence. Reflections always cause any crossover design to be "fudged" and the driver choices to be less than optimal.

In first-order crossover speakers, all those lead to a low speaker height (tweeter too close), because that's the only way to produce a decent tone balance from what is still a twisted phase response. I will not present the math for that here (couldn't even begin to), nor would I want to give it away.

That height is also too low to offset the flat-baffle/tweeter-too-close placement, which is Karls' point. One also measures a greater +/- dB response variation through the crossover region, even when sitting at that "proper" height.

Finally, the listener is often encouraged to not toe-in these speakers, so less reflections are heard in that best seat. But this reduces the strength of the center-fill, so the speakers are moved closer together. All of this makes the head position even more twitchy.

It is the reflections that steer a designer to all these choices, and away from true time coherency. But if you read the NSM and Jordan-designs reviews, you can see what coming closer to time coherence accomplishes, including clarity, dynamics, ease of placement, freedom to play all music, and to use any component, especially when the 1st-order crossover circuit employed is simple and made with high quality parts.

I am aware of NSM's/Leo Massi's/Audio Physics/Michael Green's room placement guidelines, and I do not recommend those for any speaker. Ours are closer to Cardas', as are most firms, and described in our manuals.

Got a link for you to try:
Doo Wop Horses
If the sound "clicks", erase your browser's caches and re-visit when there's less web traffic. Takes about 30 seconds to load thru a 56k modem. Let it load completely (wait for the fence to appear), then click on each horse. Whoever wrote this is quite accomplished!
Makes you remember why we want fidelity!

Best,
Roy
Green Mountain Audio

So I guess I should pass over the NSM because the drivers are too close together? I'm not surprised they aren't time coherent.
I guess this is the A-A thread;
Roy's comments on Jordan

Jordan driver speakers now don't sound like they are worth the $1,500 after reading about their limitations.

Cdc, I'd listen and decide. There are numerous people on here that have the Carolina Audio speakers that use Jordan drivers and like them. A one-way speaker has much to recommend it. Nothing is perfect.

I quote from Roy's comments on AA,
"I require more dynamic headroom, less IM at loud levels/on complex music, and more bass extension- not a knock on the good design work being done with Jordans, just a recognition of the physical limitations Jordans impose for me."

Those requirements may not be your requirements. Those are a very good description of reasons to select multi-way speakers. I use single-driver(Lowther) speakers for other reasons, and I prefer them over the compromises that multi-way speakers make. Not because they are perfect, but because I can live with their compromises in order to get their strengths.

Everything in speaker building is a compromise. What may be a "requirement" for some people, could be seen as a "detriment" to others. Every speaker designer's product is a statement about the designer's point of view on how he thinks a speaker should be made.

Make your decisions based upon what YOU need and what YOU like to hear. I recommend auditioning.