Phase Coherence or Time Alignment: Which More Imp?


This thread is really a follow on from a prior one that I let lapse. Thanks to everyone who contributed and helped me to better understand the importance of crossover design in building a loudspeaker. What I gathered from the last thread that there are opposing camps with different philosophies in crossover design. Leaving aside for a moment those that champion steep slope designs, my question is for those who have experience with speakers that are time aligned and/or phase coherent (using 1st order 6db per octave crossovers). Which is more important, phase coherence or time alignment? In other words, which more strongly influences the sound and performance of a loudspeaker? The reason I ask is because of the four speaker lines currently on my shortlist of floorstanders, three are either phase coherent or time aligned or both. The Wilson Benesch Curve's/ACT's and the Fried Studio 7 use 1st order crossovers but do not time align the drivers through the use of a slanted baffle. The Vandersteen 5's and the Quatro's both time align the drivers and use 1st order crossovers. I guess what I am asking is do you need to do both or is the real benefit in the crossover design? I'd appreciate your views.
BTW the other speaker is the Proac D25 and D38
128x128dodgealum
I have to agree with Lrsky, although I usually prefer not agreeing with anyone. The theories of speaker designs are interesting, but the actual experience is what matters ultimately. All speakers are compromises - and overall it's pretty amazing that you can etch a pattern into plastic with a cutting head, play it back with a tiny diamond, amplify that signal a gazillion times, and then have it come back at you sounding ALMOST exactly like it did going in.

I've heard many of these new "wonder-speakers" with all sorts of expensive drivers and internal wires that are just unlistenable (to me), and I've heard 20 year old designs with some updates (like my Dahlquist DQ-20i's) that keep beautiful music sounding that way. And despite whatever a designer does with Phase and Time, room interactions play a huge, huge part in what you'll actually hear.

I have heard both Joseph Audio Pearls and Green Mountain C-3's a fair bit and they're both great speakers with different attributes for people with different "ears".
I had a trade pass at the last HES San Francisco and went back and forth without having to wait on lines between Joseph Audio and Avantgarde Trios and came to the conclusion that if I had to live with one or the other at home, I'd pick the Pearls as less fatiguing - not what you would predict for a steeper slope crossover.
I also have spent a few hours audiotioning GMA C-3's and found them to be spectacularly dynamic, very detailed, and also a bit bright/forward in the mids (for my taste) - also not what you'd predict from a 1st order design.

So go figure...
Actually, I WOULD expect the 'forward' or brightness from a first order design. It's almost a sure bet that everyone who's heard THIEL would agree that they sound forward in the high frequencies. My speakers measure flat, (inasmuch as any can or will) yet the tweeter is invisible to the ear; this has the effect of making fatigue a virtual non factor. Plus older recordings, some of the sixties abortions which sound so awful, (this was the moment when engineers found the eq switch, I like to say), and they sound different than contemporary, but listenable, instead of ear splitting.
The principal design behind any speaker, should be fidelity, that is the output should equal the input, and here we're walking a fine line. A quarter of a db across a broad enough bandwidth, makes all the difference in the world tonally.
I theorize that the forwardness comes from the rather 'odd' sounds created by the multiple bandwidths covered by the drivers-- and how tonally mismatched they are in reproducing what should be similar sounds. That 'blend' of sounds creates a secondary sound, amusical to me, which I find offensive, and 'bright' as described by
Opalchip, even though he surmised that first order 'would not' sound bright.
This is based on listening to the contribution of the drivers individually, as they 'try' to play frequencies, which reside normally, well out of their range.
Theory, not scientific fact, but my ears hear the composite of each individual driver, and the sound is abberational.
Larry,

Great post.

In my opinion, the only manufacturer who really implements low order crossovers properly is Jim Thiel. His crossovers are complex, but he is much more advanced in his thinking than any other designer in that camp. If you took his speakers and ran them at moderate listening levels in a well damped listening environment and sat at just the right height you'd hear the best results that particular method has to offer.
Dear Josephaud- with my unbridled respect for you, I hubly accept this complement.
Thanks, and I look forward to seeing you again soon, (perhaps in Vegas.)
> There is no 'patent holder' per se on cross overs

Please forward your remarks to Richard Modafferi _and_ Roy Kimber, and let me know what you find. OTOH, I don't know if Kaminsky is still alive, or if that site is a licensee of his, or what. (Here's a small hint: "Our Infinite Slope (US Patent #4771466) reduces wave interference down....") God, I mean it's so obvious.

In a similar vein, your opinion that you would expect a first order crossover speaker to sound forward is without foundation. It's fine if you like Thiels, or if you like that attribute, but there are other first order designs which are anything but bright, including Vandersteens and presumably out of your awareness Symdex.

When Thiel was first getting dealers, including Herb Hamburger in PA, he maintained that other speakers rolled off the high end improperly. It was a design decision, which in my opinion he has somewhat moderated since the early days.

And most speakers do not measure flat to 20khz, although in recent years more and more might than was the case in the past.