Sloped baffle

I think that Kiddman makes good points here. There are so many interactions and variables in the design of loudspeakers that it's got to be very hard to isolate which factor results in a speaker that you ultimately love.

To wit: you couldn't have two more different small speakers than, say, GMA Chromas and Harbeth P3ESR's. "Leaky" plywood cabinet vs. synthetic stone cabinet. Metal dome tweet vs. cloth tweet. "Complex" crossover vs. "simple" 1st-order crossover. Inverted driver polarity (!) vs. not. "Radial" cone material vs. paper-composite. Flat face baffle vs. slanted baffle. And the list goes on and on.

Now, then, various audiophiles swear by one or the other of these speakers. But who can really say whether it's the cabinet material, driver material, crossover topology, phase/time coherence or (most likely) some combination of all of the above that gives the results that you get? And THEN, factor in the room and the associated equipment and the tastes and hearing of the listener and you have more variables than anyone can deal with.

So, yeah: I can see that you might become fixated on the theoretical merits of time coherence and then fall in love with a non-time-coherent speaker, anyway.

Reminds me of the joke about the unmarried scientist who feeds his theoretical preferences in women to a computer and then cross-references it to a database of women in his city. One day he approaches his lab assistant and says, "Well, it seems I have actually found the woman of my dreams. She meets every one of my requirements."
"Then why the glum face?" asks the assistant.
"I just don't like her," he sighs.

Ng... thanks for the phase coherence article. The article seems to be based on scientific controlled studies and tests. Rather than paraphrase the conclusions, I copied them here:

"So what conclusions regarding the audibility of phase distortion can we draw from the all of the above?

'Given the data provided by the above cited references we can conclude that phase distortion is indeed audible, though generally speaking, only very subtly so and only under certain specific test conditions and perception circumstances.

'The degree of subtly depends upon the nature of the test signal, the dB SPL level at which the signal is perceived, the acoustic environment in which the signal was recorded and/or played back as well as the Q & fo of any filter networks in the signal stream. Certain combinations of conditions can render it utterly inaudible.

'Room acoustics further masks whatever cues that the hearing process may depend upon to detect the presence of phase distortion."

And here's my personal bottom line. Phase coherence is just one of many variables that is taken into account when designing a speaker system ... and there are many. As many folks have said, trust your ears and audition as many speakers as you can. But ... if I was asked to buy speakers based on their phase coherence characteristics as a stand-alone factor, I personally would not.

Thanks again Ng.... Good article. It puts the issue into context.

Bruce

And here's my personal bottom line. Phase coherence is just one of many variables that is taken into account when designing a speaker system ... and there are many. As many folks have said, trust your ears and audition as many speakers as you can. But ... if I was asked to buy speakers based on their phase coherence characteristics as a stand-alone factor, I personally would not.

Bifwynne, I disagree here. Of course, you are entitled to think about this the way you choose, just as I am.
There's too much research - of the wrong type - that convinces people that time-coherence is one of the many issues/parameters to be resolved in speaker design.
After hearing time-coherent speakers vs. others, the speaker should be designed around time-coherence & issues re. that speaker's design should be solved in the context of time-coherence. When that speaker is correctly built as a time-coherent speaker it will simply be far more realistic, dynamic & accurate to the recorded music than any other speaker in its price range. From my experience, I'm convinced - there ain't no other way to go.....
Others who have also had such an experience feel the same way not surprisingly.
sorry to see that (once again) this crowd has missed the point re. time-coherence. :(
When you have a chance, listen to a time-coherent speaker (doesn't have to be Green Mtn Audio) & compare it a non-coherent speaker.....

Bif,

Don't get me wrong. Phase is taken into consideration on any competently designed speakers. My first didn't but I wasn't particularly competent then. Not yet either. Still, with four 6-1/2's per side, they sounded more dynamic than any "coherent" speakers I've heard short of the Dunlavy SCIVa. Never considered the two were related.

Time coherence implies that the first cycle of a tone is more important than the second or third. That, I'm unsure of. Really, I don't know. Low order crossovers have advantages, including transient behaviour. I like them because they're simpler and cheaper but not for all drivers and circumstances.

Here's the test... Listen to any 2.5 way speaker. By design, the woofers roll off at different frequencies and must have increasing phase separation as frequencies increase. 45 degrees by 1000 Hz is fairly typical. According to the article, where our ears are most likely to detect. The .5 woofer will be lower SPL but still audible. Can you hear any phase distortion?

Problem is that we don't hear distortion as distortion, not unless you have the trained hearing of a professional under controlled conditions. It can be measured by instruments but human brains interpret those as frequency differences and there could be any number of explanations including comb filtering, diffraction, or the driver. Almost as easily, they can be masked.

So, forget the test, it's useless. More likely that someone will misinterpret that as all 2.5's are ....

Ngjockey and Bombaywalla ... I find the issue of phase coherence to be intellectually interesting. I also find Roy's article and the article Ng... provided to be equally interesting. If I had the time, if there were more B&M stores around with a variety of speaker types, and if the salepeople were game to burn time to experiment, I'd love to build up a personal anecdotal portfolio of experiences.

To date I have only one data point, which is almost useless. I spent 90 mins about 2 years ago with Vandy Treos. They just didn't do it for me. Imagaging, soundstage and musicality were nonextant.

And if the pushback is that they weren't set up correctly, or wrong cabling, wrong positoning, not leveled, and so forth, my response is .... still not impressed. Even if the Treos would have taken me to the 8th dimension if all the foregoing variables were controlled ... I am still not convinced. I want to flip the switch and listen to music. Not interested in using an oscilliscope to figure out how to enjoy music.

This is a fascinating thread. I hope it will continue to attract more comments from folks who have relevant experiences.

BIF