Sloped baffle

Just a supplemental fyi, here JA's bench test measurements for the Revel Salon 2:

http://www.stereophile.com/content/revel-ultima-salon2-loudspeaker-measurements

And one more, the might Magico Q7:

http://www.stereophile.com/content/magico-q5-loudspeaker-measurements

If nothing else, perhaps someone can explain how to properly interpret what these measurements mean. They do not look like the Vandy 7.

Bifwynne,

Ok ... if Tim or Bombaywalla catch this, here the ultimate Q. How can one tell whether a speaker is time and phase coherent?

Critical listening is one of the methods - when a speaker is time-coherent then it will get the timing right for ALL genres of music. Recordings otherwise painful to listen to will be less painful (because the speaker is not distorting the music signal coming to it). In time-coherent speakers you forget the audiophile attributes (pin-point imaging, soundstage width/depth/height, etc, etc) & you focus on enjoying the music.
The other method, as stated by Unsound & 2nded by Al, is the time-domain step response. Usually Stereophile (as indicated by Al already) & Soundatage reviews http://www.soundstage.com/index.php?option=com_content&view=article&id=16&Itemid=140 do a pretty good job of showing all the measurements they have done on various loudspeakers they have resp. reviewed.

Thanks Tls49 - you have pointed Bifwynne to a really good website for reading on time & phase coherence. I always look to Roy Johnson when I have questions on this subject. To me he is skilled in this field & has dedicated his life to making time-coherent speakers since he began his biz in the 1980s. Green Mtn Audio speakers are the only speakers that I know of that are time-coherent across the entire audio band from my personal experience. I know that several people believe that Vandersteens & Thiel speakers are also time-coherent - I personally do not have any experience w/ either of those brands so I will not comment.

First, the Vandy 7's step response plot shoots up like a rocket and then quickly rolls off and stays down. By contrast, the Studio 2 shoots up, rolls off and then rolls back up again. What does this mean? Why the differences?

Why the differences? Because the Vandy 7 is time-coherent & the Revel2 is not!
Bifwynne, if you click on the link provided by Tls49, you will see exactly why as you read the text there. Scroll down where Roy J talks about time-domain response & he shows how a step response looks when the speaker is time-coherent & when it is not.
The Revel2 are clearly not time-coherent.

I'll ask again, how important is time and phase coherence?

To me it is everything! I used to own B&W speakers & I have heard speakers from many, many different brands now both auditioning at dealer locations & at multiple RMAF shows, at various friends' homes, etc.
The sonics from a time-coherent speaker are in a totally different league. For me time-coherent speakers "get it" while all others simply do not. Once I heard Roy Johnson's Green Mtn Audio speakers & owned one for many years, I realized what the heck time-coherence was all about. Now, I cannot listen to any speaker if it's not time-coherent - very quickly I will realize the lack of time-coherence & I will immediately perceive that the music has no life & no PRaT & to me it will just good/superior sonics but not music. I want music from my speaker & not good/superior sound - I didn't pay top $ for good/superior sound; I paid top $ for music thru the speaker. These days I stick to time-coherent speakers - my selections are very few but it's worth every penny to me. This should be the case for everyone if you are interested in listening to music. Many of friends are into superior sound (& not music) so they are on a perpetual merry-go-round for speakers - speakers come & go thru their music rooms. They are always wow'd by a new speaker & later after a few months or a year, that speaker is sold & another one takes its place & the cycle repeats. In my mind I'm thinking that I've made my case for time-coherent speakers - you buy it once & then you sit back & listen to music because a time-coherent speaker will play every genre without tripping up because its physics is right.
Of course, IMHO. YMMV.

06-22-14: Bombaywalla
Why the differences? Because the Vandy 7 is time-coherent & the Revel2 is not!
Bifwynne, if you click on the link provided by Tls49, you will see exactly why as you read the text there. Scroll down where Roy J talks about time-domain response & he shows how a step response looks when the speaker is time-coherent & when it is not.
The Revel2 are clearly not time-coherent.

I agree.

Bruce, taking the Magico Q5 as an example, whose measurements you also linked to, note that the frequencies of each of the four up and down oscillations that are shown in the step response figure become progressively lower (i.e., their periods/durations become progressively longer). That is because the first peak primarily represents sound arrival at the measurement mic from the highest frequency driver; the second peak primarily represents sound arrival at the measurement mic from the next highest frequency driver, and so on.

So it can be inferred that the amount of delay between the start of the arrival of the sounds from each of those drivers and the occurrence of the step in the signal that is sent into the speaker are significantly different, and become progressively longer for progressively lower frequency drivers. While with the Vandersteen 7 they are not significantly different, resulting in the outputs of each of its drivers summing (at the position of the measurement microphone, at least) to a much closer approximation of an ideal step response.

Best,
-- Al

Just a word of caution regarding some speaker measurements one might come across. In an effort to avoid room interactions skewing measurements, very often speaker measurements are taken closer to the speaker than where one would typically sit. Most speakers designed for time and phase integrity need to be taken further away to allow for driver integration (approximately 8'-12'), where listeners typically sit. Unless these further measurements are taken in an anechoic chamber, the room will now contribute more measurable distortions than if the same measurements were taken closer to the speaker. Most people don't listen to speakers at the distances many speaker measurements are taken. If speakers with time and phase integrity aspirations are measured at distance ranges other than where they were intended to be heard from; their square wave and step response, though probably still better than competing speakers without such design considerations, will have their ultimate measurable potential be compromised.

Bombaywalla, I'm somewhat familiar with NRC test facility. But I am not sure which of the NRC tests speaks to time and phase coherence.

Btw, I surmise that the reason many of the top speakers, like the Magico Q5, that have flat frequency response plots and probably use higher order cross overs is because the driver timing is tweaked at the cross over points to optimize wave cancellation and augmentation. But ... the drivers are not otherwise in phase outside of the cross over overlap region.

So ... even if the speaker specs well on the bench, it may very well be distorting complex sound patterns as Roy Johnson explains in his articles.

Bombaywalla, did you or Tim mention that one mark of a phase coherent speaker is one which has a flat impedance and phase plot. Take a look at the Magico S5's specs. Is there anything else apparent from the NRC tests that permit inferences about phase coherence?

http://www.soundstage.com/index.php?option=com_content&view=article&id=1043:nrc-measurements-magico-s5-loudspeakers&catid=77:loudspeaker-measurements&Itemid=153

Al, here's another Roy Johnson article I clipped. Perhaps if you get a chance to read his articles, please share comments and thoughts:

http://greenmountainaudio.com/speaker-time-phase-coherence/

Btw Al, you may find the square wave pics in the article to be of interest. It seems that using higher order cross overs creates an almost unsolvable electrical problem.

BIF