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
dodgealum
Thanks to you both. Let me see if I understand this correctly. Phase irregularities caused by steep slope crossovers can be compounded by an alignment of the drivers which further distorts the arrival of sound waves at your ear. What I am wondering is which tends to have a greater impact on phase coherence--a steep slope crossover which delays the sound eminating from certain drivers or a poorly conceived alignment of the drivers? Let's take the new Fried Studio 7 for example (photos are on the website). It has a flat baffle with the tweeter flanked on top and bottom by a 6" midrange (top) and an 8" woofer (below). Is this a time aligned (or as Richard Hardesty would say "temporally aligned") arrangement? If so, great. If not, how much of an impact does this have on phase coherence? In other words, if the drivers are not temporally aligned then are the supposed benefits of 1st order crossovers lost due to improper driver alignment? Or is the phase coherent crossover 90% of the battle and the lack of temporal alignment only a small piece of the sonic picture?
Also, can we really hear these phase irregularities or what? Some say we can and others say impossible. All I know is that the phase coherent designs I've heard sound more like live music than designs using steep slope crossovers. I was at the NY Hi End Show last weekend and it was very interesting for me, after reading through the dispute between the "steep slopers" and the "first order crowd" in the previous thread, to walk back and forth between the Joseph Audio room (a steep sloper) and the Vandersteen Room (a first orderer). They were right next door to each other so I could drift back and forth. The rooms were identical. Both used (different) but high quality upstream components. Here is what I observed. The Joseph Audio room sounded like hifi and the Vandersteen room sounded like music. I could point out other specific differences that I heard but this pretty much captures the essence of my experience. I'm not prepared to say the this essential difference was due purely to the crossover designs of the two speakers but it may have SOMETHING to do with what I heard.
There are far too many variables from one system to another for you to conclude that the crossover method is the root cause of the difference. Our speakers are used by many discerning professionals who know what live music sounds like, since they are exposed to it every day.
Jeff, I totally accept your position. Having initiated the thread on crossover design (on which you were a gracious participant) I just thought it interesting to go back and forth between the rooms and listen to the two top models of reputable brands' that approach the crossover differently. I realize that other factors contributed to the differences I heard. I'm just wondering to what degree those differences are attributable to the diametrically opposed crossover designs. One thing I did notice was that the Joseph Audio Pearls seemed to image with greater precision than the Vandersteen 5A's. Localization of individual instruments was much easier. The images on the Vandy's seemed to float around. They weren't anchored in position as they would be live. On the other hand, the soundstage depth and width of the Vandy's was, to my ear, far superior to the Pearls. I wonder if others have had similar experience listening to either of these models and whether, again, the crossover design is in part to blame.
I don't believe you can demonstrate that having a time and phase coherent speaker is more important than having a just a phase coherent speaker. The problem in being definitive is not merely that it's largely a matter of preference - which it is, just like I prefer Patti Smith to Norah Jones - there are unresolved matters of psychoacoustics in testing something like this, as well as a particular design method's suitability to a particular use. For example, a time aligned speaker might not be appropriate for extreme near field listening; it objectively wouldn't be the best for that situation. But it might be the best in another situation.

Of course, Jeff J. thinks each kind is less appropriate for virtually every situation.