Questions Re: Time & Phase Alignment


Some basic questions here. Hope nobody minds. Some of this stuff I don't quite understand. Have recently become very interested in T&PA after hearing both the Green Mountain C3 and Thiel 3.7 at RMAF, both of which tout this design quality and both of which were among the best speakers I've ever heard, anywhere.

Questions:

1) Basic definitions. Time-alignment means that sounds that start at two different drivers at the same instant will reach your ears at the same instant.

Phase-alignment means that there are no phase errors between drivers: the same frequency waveform, for example, produced by two drivers (in their overlap region) will be entirely in phase with each other (and thus completely reinforcing).

Are these definitions correct, correct but lacking, incorrect, or what? I find there is a lot of either misinformation or misunderstanding in the industry about these things.

2) How does a sloping baffle produce time-alignment? I really don't understand this - I would think that having the voicecoils of all drivers in the same plane would, in fact, produce time-alignment. Is the slope to compensate somehow for the crossover?

3) On that note, I don't understand why it is that 1st-order crossovers are phase-aligned. Perhaps this is stricly due to the implmentatation - a single cap produces no phase delay? But I don't think that's the case... so why is it that 1st-order xovers are said to be p-aligned and higher-order xovers are not...? Or is that, perhaps, myth?

3) Thoughts on the superiority of coincident midrange driver/tweeter vs. completely separate drivers? I certainly see the benefits of the former but it must introduce some problems as well - there must be distortions caused by the entire tweeter assy moving with the mid driver.

Thanks much in advance to someone who can shed some more light on these topics.
paulfolbrecht
(Speakers which are) full freq-response, multidriver, dynamic, and time and phase-aligned
That's a tall order, my friend.
I strongly recommend you forget it: multidriver, & phase + time aligned don't go together. You will laways have phase matters with many drivers.

Well performing full-range passive spkrs are extremely expensive. Often they are not practical; heavy, difficult to drive, to place, subzero waf, etc.

If I may be so bold, ENjoy what you have. Cheers!
Paul, I own the new GMA Calypso's and they are very, very impressive speakers. I agree with others that say search the archives here for comments by "RoyJ" (Johnson of GMA) and also by "Karls" (Karl S. of Audiomachina), both very well versed on time/phase coherence. To my ears (30 year musician) a time/phase coherent speaker like a GMA brings you closer to the music than a non time/phase design. Once you own a pair of time/phase coherent speakers, you will find it pretty much impossible to go back. My opinion only.....for what it's worth to you. E-mail me if you have any questions I can answer for you about the Calypso's.
Paul, you are certainly on the right track in terms of the design principles that should ultimately lead to true fidelity in a loudspeaker. Unfortunately, there are always tradeoffs in every speaker design, and every implementation of a given principle has variables that lead to differentiating sonic results. In other words, there are no perfect speakers.

I am a huge fan of time alignment and phase coherency, evidenced by the fact that for the past 27 years I've owned a pair of Beveridge Model 2 SW loudspeakers. These are full range electrostatics with no crossover ( I eliminated the high pass X-over) save for the low pass on the subwoofer. This speaker probably comes as close to a perfectly time aligned and phase correct speaker as any design ever made, but it still errs in ways important to music reproduction.

The bottom line is, whether a speaker's design is critically time aligned and phase correct or not, ultimately it gets down to how you perceive its ability to reproduce music. I have long admired Theil's work, but at Theil's RMAF demonstration this year I was most disappointed in the sound of the new 3.7s. To me, they had a coloration to their sound that was akin to holding a long piece of tin foil between two fingerand shaking it. Everyone who heard it at the same time that I did reported hearing the same coloration. However, someone from our group who heard it later didn't experience it that way, so maybe there was something else contributing to that phenomena that was later remedied.

The GMAs are very fine speakers, and the C3s, when set up properly, rival my old Beveridges (I spent quite some time auditioning them with Roy last summer at his facility in Colorado Springs). Roy is an extremely competent designer, as is Jim Theil, but between the two, Roy's would certainly get my vote. Of course, YMMV.
songwriter72, what are you driving your Calypsos with?

Theloveman (hmm.. I feel slightly uncomfortable calling you that), I thought the Thiel 3.7s were very impressive. Not as good as the C3s, but very, very good speakers.

Sounds like you are referring to Al driver "ringiness"? It has never bothered me... I can notice it when I try, but it has never bothered me.

I've read that long thread that included the "battle" between Roy & Jeff Joseph. Kind of ironic, their opposite takes on T&P, as some of my favorite speakers are made by both. I used to have Joseph Rm25s which are very good speakers. I've also heard the Pearls, which were pretty amazing. That said, and although I'd heard them years apart, the Pearls do not stand up to Roy's all-out effort, the C3s, which, of course, take T&P into account.

I bought a pair of Continuum 1.5s used. May keep them, may not. May end up in my 2nd system. We'll see.

Heard some VMPS RM30s today at a local owner's house that were pretty impressive. Very good sound all around.
Paul,
Using an Arrogon solid state amp here. I'm thinking of going tubes, but I live in Hawaii and it's warm enough here as it is.