Phase Coherence or Time Alignment: Which More Imp?

"Phase coherence" and "time alignment" are related concepts.

I think what you're thinking of as time alignment is aligning the acoustic centers of the drivers with either a stepped or slanted baffle. This "phase aligns" them, so to speak. (Differences in phase are differences in time. Don't forget that a typical plot of a sine wave has two axis - amplitude and _time_.)

It's possible to have alignment without a slanted or stepped baffle. You have to look at what the listening axis is, and see if the extra distance between your ear and other drivers spaced farther away will make up the alignment.

Let's take a 2-way (TM, not MT) as an example. The woofer's acoustic center is 5 feet away from your ear. The tweeter's acoustic center will be farther forward. Step the baffle to put the tweeter farther back and you get alignment. Or tilt the front baffle back and you also get alignment of the acoustic centers.

Now lets assume that the woofer is at your ear level. So it's 5 feet away. The tweeter is 10" above the woofer on the front baffle. You now have a triangle with 3 sides, 60, 10, and 60.8. Just by the increased distance to your ear, you've done the equivalent of moving the tweeter back.

I'm sure that the designers of the Studio 7 took this and other factors into account, and that they're a minimum-phase design.

Partially true. In a hurry today so I'll be brief and general.

Time alignment generally refers to the alignment of the theoretical point sources of all drivers in a cabinet, such that the signals emanating from them at one moment in time all reach your ear at the same time. The sloped or stepped baffle tries to accomplish this - but of course, if you're not at EXACTLY the right seating height for that particular geometry, and EXACTLY the same distance from both speakers, and have no near field room reflections, much of the benefit is lost.

Phase Coherence problems are mostly created by crossovers as they split the frequency bands. So a time aligned speaker is no more likely to be phase coherent than any 2 or 3 way speaker, unless much care, measurement and testing and re-testing and re-testing goes into the crossover design. Without that - even though what's leaving the tweeter and the woofer may arrive at your ear at the same time, the signals from each have probably lost their phase "alignment" while travelling through the crossover and drivers.

There is some dispute over whether you could actually hear this if a crossover had a true infinite slope. But since the reality is that there is large overlap in the midrange where the woofer and tweeter are producing the SAME frequencies, if they're out of phase with each other it's bad news. In a worst case scenario, in an anechoic environment, they could perfectly cancel each other.

Not a thorough explanation but I have to run. I'll bet Roy frm GMA has expounded on this somewhere already.

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.

Steep slope crossover.

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.