Does Time alignment and Phase coherency make for a better loudspeaker?

I learned this past year how much diffuser panels helped with imaging.  Diffusers on the back wall brought the imaging into much sharper focus.  The next step was putting my speakers on springs.  That not only improved the bass but also increased detail and focused the soundstage even more.  Controlling room reflections has a big impact on imaging.  The springs isolate the speakers from the floor and reduce speaker cabinet ringing.   I saw the difference with accelerometer FFT plots.  As minor as that seems it makes an audible difference.  And remember, the Thiel speakers have a mineral front baffle that is very rigid but still benefitted with isolation.  

@tomic601 , You are looking at it the wrong way tomic. It has nothing to do with musicians on stage. Each instrument is a singularity. Lets take a bass drum. When the pedal hits the drum there is an attack followed by the primary resonant frequency of the drum. Some drummers dampen this which I think is a shame. The attack is at higher frequency and can get caught in the crossover frequency of subwoofers. If the sound of that attack reaches you at different times from the subwoofer and main speakers you first smear the attack and if the delay is long enough you get an echo. Improperly timed subwoofers numb bass transients. Also remember that time shifts phase. Everyone knows what happens if you shift phase 180 degrees. If you don't, wire one of your speakers backwards and listen to what happens. The effect is much less obvious at higher frequencies but it is there. listen to what happens to the image. In order to shift phase 180 degrees at 100 hz you would have to move a main speaker 5 feet forward or backward. This can easily happen with some set ups. Using a swarm system is a way around his problem. 

Even Levon Helm's ( RIP ) brilliantly damped kick drum has harmonics and reflections that allow the human ear to locate it and ascertain the acoustic reverberant space it is located in. Time and phase information in the waveform that makes it to the ear ... or not..  

I learned this past year how much diffuser panels helped with imaging.  Diffusers on the back wall brought the imaging into much sharper focus.  The next step was putting my speakers on springs.  That not only improved the bass but also increased detail and focused the soundstage even more.  Controlling room reflections has a big impact on imaging.  The springs isolate the speakers from the floor and reduce speaker cabinet ringing.   I saw the difference with accelerometer FFT plots.  As minor as that seems it makes an audible difference.  And remember, the Thiel speakers have a mineral front baffle that is very rigid but still benefitted with isolation.

What does ^that^ have to do with time/phase alignment in a speaker?

It is almost implying that a speaker which is not time/phase correct only need springs and wall treatments.

Or another spruiking of the springs for the Nth time.

sometimes

It all depends on how the designer achieves T/P coherency. 

You cannot achieve T/P coherency with room treatments. 

i have modest specimens of 3 time-and-phase-aligned speakers -- one by magnapan, one by thiel, one by vandersteen, and they all image equally well [IOW when fed the right material they all seem to "disappear" leaving just the stereo image] to my ears but each has different requirements for listening room space and placement. the only ones that actually work in a small room, are the thiel and the maggie speakers. the vandy needs LOTS of space, no less than about a 300 sq/ft, in smaller rooms they get shouty at the crossover point [2.8kc] and totally lose their magical stereo imaging. i also have a mirage omnipolar and although i don’t guess they are time/phase-aligned, they image even better than the other 3 in my experience, again only if you give them plenty of space around them even though you can listen to them in the nearfield and get quite a spectacularly stable 3D stereo image that way with a wide sweet spot.

Room treatments do not add to coherency.  Room treatments subtract.  The speaker must produce a time or phase coherent sound field in order to produce that astonishing three dimensional soundstage.  The reflections- both airborne and the mechanical interaction between the speakers and the floor (as well as to the amps and other components) though small they may be smear the sound.  The room treatments remove those reflections to restore coherency and detail as well as bring more clarity to the bass.  That is my experience.  

No, these things don't on their own, make for a better speaker. It's not like this hasn't been studied for years. 

https://www.audioholics.com/room-acoustics/human-hearing-phase-distortion-audibility-part-2

^It might be imprudent to overgeneralize conclusions from this research. A loudspeaker that is phase coherent might not be time coherent, though a loudspeaker that is time coherent will be phase coherent. That there was some evidence reported (though deemed staticaly irrelevant)  of discernment of phase coherent recognition, then asks an unanswered question; were the correct responses consistently from consistent respondents?

From years on this forum, if there’s anything that I’ve learned, is that it would appear that while we all hear somewhat similarly,  many of us seem to listen differently. For what ever reasons whether consciously or subconsciously we often times prioritize different things when listening, and are more sensitive to different aspects of sound. I believe that some are more sensitive to time and phase coherence (perhaps at the expense of other attributes) than others. For those that are, I suspect that time coherence allows for a greater appreciation of transient detail, and a quicker neurological processing of soundstage and imaging cues as they are presented in real time.

A proper step response (in an appropriate space, at an appropriate distance) is perhaps the best indication of a time correct loudspeaker. John Dunlavy had said that once a a proper step response is achieved, everything else starts to fall in place. This suggests to me that time coherence could have advantages beyond the specific goal at hand.

Some have argued that time coherence only works for given listeners in specific locations. Adherents would argue that they work just as well as non- time coherent loudspeakers for listeners in less than ideal locations, but non- time coherent loudspeakers can never really work for any listeners at any locations.

In the past, making time coherent loudspeakers was a daunting project, that not many were capable of and/or were not deemed worth the effort. I suspect that as DSP and more integrated loudspeakers become more prevalent, so will time correct loudspeakers become more prevalent.

Every other component in the chain can maintain time cohernence without corruption, why not loudspeakers?

Past attempts at DSP were abysmal failures, but perhaps significant gains have been made in the past few years. Funny I still dont consider DSP a viable option which is probably not wise. Just dont like the idea of DSP at a fundamental level. 

@audition__audio , that is your own bias at play. It is just about numbers, ones and zeros. The very first step in the modern recording process is turning the music into those numbers. Once you are in numbers you can do just about anything without any added distortion. It is all about the programming which has improved over the past 30 years but the basics were well known 30 years ago. 20 years ago some very sophisticated processors were available but the mentality of us audiophiles shunned any added complexity. Our culture was used to the problems of analog devices and I think we generalized those problems to digital devices.

The improvements that can be made with digital processing far outweigh any downside. I digitize my phono stage to run it through a digital preamp/processor. You can go back and forth between the analog turntable and the 192/24 digitized one all day long and you can not hear the difference. The two major advatages of digital processing are being able to adjust frequency response, matching channels precisely and digital bass management with time and phase correction. IMHO you can not get to state of the art sound without them. Another way of looking at it would be, you can make any system sound better with digital processing. Also you can not get to state of the art sound by listening. You have to measure.

^The subject of DSP is perhaps for another thread. But, as pertains to the subject at hand; DSP can be make available time and phase coherence to those that wouldn't otherwise have the considerable chop's necessary to accomplish it, and make it much less time consuming to develop and considerably reduce the labor costs to implement it.

It seemes to me, that if all else was equal, but one speaker was not time and phase alligned, and the other was, the one that was would sound better.

And I even have a bit of pretty strong evidence that this is the case.

The late Jeff Bagby, well respected speaker designer (professionally, and among DIY’s), designed 2 versions of the same speaker using the great SB Acoustics Sartori drivers.

The Kairos, which is time and phase alligned, and the Adelphos for those that are intimidated by building a cabinet with a slaneted baffle. There are also crossover differences, too, in order to compemsate for the flat vs slanted baffle.

Here are the kits and write ups:

Kairos

Adelphos

My friend and I built a set of both speakers, and compared. No question, the Kairos imaged better and created a bigger soundstage than the Adelphos. Other than those parameters, other aspects sounded, to our ears, identical.

And let me add, as with most well designed DIY speakers, the end result with both the Kairos and the Adelphos, are speakers that end up sounding as good as commercially available speakers at several times the money spent.

To my ears, I've never heard a better sounding pair of speakers than my Dunlavy SC-Vs. I started out with IIIs, then IVs, and finally my Vs. Once you hear proper time-aligned, phase-coherent speakers, and get used to them, you'll probably never want to go back to anything else.

I'd owned B&W 802 S3s for 18 years before I bought my SC-IIIs in late-summer 2019, and it took a little while for my ears/brain to get used to what I was hearing on the Dunlavy's. Once I got used to the Dunlavy 'sound' I couldn't go back to the B&Ws. The IVs were even better than the IIIs, especially in the bass, and the Vs are an bigger improvement over the IVs, than the IVs were over the IIIs. 

The Dunlavy's are incredibly accurate speakers; but they can be brutally honest on bad recordings. They don't have any colorations, so if you're used to a certain type of sound that isn't incredibly neutral then you may not like them.

 

I agree with Millercarbon. Phase and tme alignment is critically important, but when it compromises other aspects, then you will get a less than desirable effect.

BTW, absolute phase and time alignment is IMPOSSIBLE to achive for the entire spectrum of 20Hz-20kHz. Phase correct means only that the crossover regions are not out of phase.

Time alignment also applies only to limited frequency ranges... 

Nevbertheless, when a manufacturer is aware of these parameters, and stirves not to make blatant errors in these areas, it does make for vastly better speakers compared to those where the manufacturer is unaware of these issues.

;

actually phase accuracy in the rest of the chain is difficult and requires an engineer with ears deeply involved in the listening and design process... Charlie at Ayre comes to mind... No global negative feedback.... think thru what NFB is, how it works and what positive and negative aspects it can have.... Of course we owe Dr Otalla a debt of thanks for derailing the THD crowd.... The T in TIM is all about time... ( a quiz of sorts ). I have a variable NFB amp ( RIP Roger, you were a genius )... Assuming level matching, the changes to stereo image across various NFB is apparent.

Carry on ! enjoy the music.

I learned this past year how much diffuser panels helped with imaging.

So many have spoken out about room treatment, and I was convinced to try some out for myself. I finally manged to complete and install some quadratic diffusers from plans, and I am surely glad I did.

With absorption and diffusion, (and I have a lot of scope to dial it in much better) the presentation is giving me a better understanding of the advice and benefits shared here in Agon

@tomic601 , An engineer does not need ears to develop a phase coherent loudspeaker, just a measurement microphone.

In order to be accurate (I did not say sound good) a speaker has to start with a flat frequency response and be time coherent which as unsounds relates assures phase coherence. Unfortunatly, for speaker designers this has to include the room the speakers are set up in. For state of the art accuracy one has to be able to adjust frequency response so that the speakers are flat from 20 Hz to 20 kHz. This also assures that both channels have exactly the same frequency response which is very important for imaging. If a subwoofer is added one has to make sure they are time coherent with the main speakers. The only way all of this can be done is with digital signal processing. Afterwards the frequency response can be adjusted so the system sounds good to the owner. I like mine up 5 or 6 dB at 20 Hz and down 6 dB at 20 kHz. Done this way the difference between speakers is based on the way they radiate into the room and what kind of source they are point vs line.

Generally, speakers with controlled radiation patterns sound better because they cause less room interaction. Horns, dipoles and line arrays come to mind. Omnidirectional speakers require much more room treatment and produce a smaller soundstage like sitting at the back of the hall. This can sound quite natural depending on the recording. 

@mijostyn ^that^ is all well put.

a few points

flat frequency response is easily obtainable in front of speakers but if the idea is to make a loudspeaker sound good, truly flat frequency response is the wrong goal (google ’bbc dip’)

time coherence is only meaningful if delivered at the listener’s ears, which is not so easy in a domestic listening environment

phase response/inversion has rarely made a major difference in the sound in my own experience (many hifi units allow for remote switching of phase, so it can be very easy to test for oneself)

lots of the things about speakers and what makes them sound good are hard to measure, so as in many things in hifi audio, measurement based criteria are necessary but insufficient conditions for a pleasing result

@jjss49 , flat is always the best place to start. It is a reference point from which adjustments can be made to suit. You can tell me you like your bass boosted 3 dB. 3dB from where? Frequency response and group delays can be easily measured with a $300 microphone and computer program. What can not be measured is the speaker's radiation pattern but this can be determined exactly from the design of the speaker. It is important to remember that the room, the speaker and where the speaker is in the room have to be considered as a unit. Frequency response curves can change dramatically just by moving the speaker a few feet. Identical speakers will have different frequency response curve depending on where they are in the room. Even in what appears to be a symmetrical room they will measure differently. It seems that only people who have no experience measuring loudspeakers in rooms think good sound is hard to measure. Once you know what type of      soundstage you like and choose the appropriate type of speaker, assuming the speaker is well designed you optimize the system in your room by measurement. You can not get to the most accurate sound without it. You start with accuracy then tune it to sound good to you.  If you have a shrill recording and have to ability to punch in a Grundy Curve (BBC curve), wonderful. I have one on a preset if I need it.

It's harder than not so easy to have time coherence at the listener ears in a home environment unless your room is an anechoic chamber. It impossible because of reflections and the inconvenience of having two ears. 

Mijo - measure and listen, not that difficult

you missed the essential point " rest of chain "

time and phase are just part of the magic since 1977.... 

The human ear brain processing can differentiate between the initial primary sound and the reflected sounds so long as there is enough time between those sounds. Something that microphones are challenged to do. Which is not to say that microphones and the measurements they gather are not important. Just the opposite. The vast majority of manufacturers of time coherent loudspeakers recommend pulling their loudspeakers out from nearby walls for this very reason. Those time coherent loudspeakers that are meant to be placed in, on or near the wall are designed with an understanding of the unique predictability of the affects of this proximity that would not otherwise be available with all the differing variables of users placement and variables of users rooms, and  compensation is built in accordingly.

@jjss49 , flat is always the best place to start.

not debating that point (starting point, reference point) - my statement refers to aiming for a perfectly flat measured speaker response as a sonic end point

The human ear brain processing can differentiate between the initial primary sound and the reflected sounds so long as there is enough time between those sounds. Something that microphones are challenged to do.

So true. I once challenged a dipole mic, which sound came first? Said it could go either way. The condenser mic would only say, "No." The omni of course gave a much longer answer, "Yes." Tried a tube mic, pretended at first not to hear me then started glowing red hot. So I gave up, and haven't challenged one since.

A wise old uncle once told me,  "If you can't dazzle "em with brilliance, baffle  'em wth bulls__t."

...my statement refers to aiming for a perfectly flat measured speaker response as a sonic end point

But the thread is about the time domain performance of a speaker.

One cannot change that too much with DSP. The impulse response can be cleaned up somewhat. But in the edges of the crossover bands it is not really possible to do much in a passive system compared to an active one.

Once the non-time/phase aligned system and the time/phase align systems are in place, then either/both can have the frequency response dialed into what ever is asked for.

And the question then that the OP sort of asked is, "will they sound different?"

Y’all get the crappy lossy cabinet output shows up in the impulse response, and more importantly the waterfall...right ? All easy to hear.

Mijo in 1983 I was using an FFT program on a Commadore PET in the design of loudspeakers.... I feel like Lew... hackles and all

But the thread is about the time domain performance of a speaker.

One cannot change that too much with DSP. 

With my DSP controlled active speakers I can set them to linear phase or low latency the former is delayed 30ms to align the drivers the later turns off linear phase for a 3ms delay. I can't tell a difference but my room isn't an anechoic chamber. 

Ever heard any of John Fuselier’s loudspeakers from "back in the 80’s"? Time and phase aligned, with excellent coherency and pulse response. Soundstaging and imaging were exceptional. Spectral balance varied between different iterations/models, but all had an uncanny ability to sound real. If you are familiar with them, then you should know exactly what I am talking about.

Time alignment is about when the sound reaches your ears from the drivers in your speakers. Getting it right adds realism to the sound. Wilson Speakers are built to be listened to time aligned. The smaller models are not adjustable in that regard and require a setup within some relatively tight parameters to sound best. Not to far from the listening posistion or too high/low. The middle and upper models have adjustable modules for each driver alowing more flexbility for the seating posistion and room size. Is it night and day? Yes if you are used to listening to your system with $50K and up speakers, well set up and driven by really good amplification and sources, so at least six figure system. Otherwise, not so much. This is a final touch for well designed systems.

Just tilt your head back to the desired angle..voila, time aligned 😉

I phase and time align every concert venue I mix (hundreds overe decades) , and my home rig also. I never said phase and time don't matter, I simply was pointing out that live music with no sound reinforcement is never specifically adjusted for time and phase, and it still sounds great. Musicians hopefully play in sync and in tune, but not always perfectly and it can still like magic.

That's "over" not "overe."

Also, "still SOUND like magic." Jeeze....

the fundamental problem with any question like this is of course any one element of successful design can matter, but the specific impact of that element can only be felt only if all else is equal... design of something as complicated as a loudspeaker is highly multi-variate, so ’all else’ is never ever, ’equal’, far from it in fact ... so it ends up being an interesting theoretical discussion with little to no real world applicablity

'does the type of insulation matter in how an interconnect sounds'?

'will a different brand of capacitors in a linestage improve the sound'?

'do r2r dacs sound better than delta sigma ones?'

and so it goes, round and round...

Room treatments do not add to coherency.  Room treatments subtract.  The speaker must produce a time or phase coherent sound field in order to produce that astonishing three dimensional soundstage.  The reflections- both airborne and the mechanical interaction between the speakers and the floor (as well as to the amps and other components) though small they may be smear the sound.  The room treatments remove those reflections to restore coherency and detail as well as bring more clarity to the bass.  That is my experience.  

Good for you, but the topic was time and phase... so you are out of sync.

Past attempts at DSP were abysmal failures, but perhaps significant gains have been made in the past few years. Funny I still dont consider DSP a viable option which is probably not wise. Just dont like the idea of DSP at a fundamental level. 

So you were bit biased?

I phase and time align every concert venue I mix (hundreds overe decades) , and my home rig also. I never said phase and time don't matter, I simply was pointing out that live music with no sound reinforcement is never specifically adjusted for time and phase, and it still sounds great. Musicians hopefully play in sync and in tune, but not always perfectly and it can still like magic.

 

The signal from a person playing or singing is, by definition, time/phase aligned.
If there is no speaker reinforcement, then why are you there?

Little snarky there holmz...I was referring to the sound of multiple musicians playing the same music with space between them. I attend concerts I don’t mix, and ones I do mix I listen to unamplified sound from various areas during sound check including right in front of or on the stage. If you can’t understand my posts, why are you here?

An argument I've heard for time/phase alignment is that it relieves your brain of the burden of reconstructing the sound as it originally was.  The various frequencies that make up any sound are normally all related in time and most speakers don't preserve the relationship.  Your brain is good at fixing this before you perceive the sound so you don't exactly hear the difference but you can sense the relief of your brain not needing to do the work.  

I don't know if it's true but there are sure a lot of people that like Thiel, Vandersteen, etc.  If I perceive it, and I think I do, it's a relaxing quality that other speakers don't have in my experience.  It sounds more correct and I can just relax and listen.

it does seem that snippy and snarky are in fashion, unfortunately - i fall into the rut occasionally as well

as for time alignment allowing the brain to work less hard, maybe so, dunno, but while i would agree that vandy's are very relaxing to listen to, my recollection is that thiels are less so, in fact they are quite dynamic and can get edgy, so not sure time alignment is behind their characters (more likely the metallic tweeter used in thiels)... other speakers are lovely and relaxing - harbeths, spendor classics, grahams... those are not time aligned

actually the major difference is the Jim T objective to be flat at the listening position vs at 1m for Richard V. One can debate the merits of both. Until recently i owned both and while i prefer the Vandy, I can understand the allure of increased treble energy inherent in the JT approach.

For those interested , no violin in flat at both 1m and 3 m...... of course if your reference is 32 track studio stuff, keep chasing your tail....

Most of Thiel's speakers have demonstrated to me how a single aspect which I think is incorrect can sour the entire speaker and the listening experience. I could never get past the aggressive/forward quality of the treble. To me JT efforts to achieve time/phase alightment did so at tremendous expense. Check out the complexity of many of his crossover designs. 

Little snarky there holmz...I was referring to the sound of multiple musicians playing the same music with space between them. I attend concerts I don’t mix, and ones I do mix I listen to unamplified sound from various areas during sound check including right in front of or on the stage. If you can’t understand my posts, why are you here?

I am not always the model of all things Buddhist, which is also why I asked the question ending in the question mark.

As there no way to adjust non sound reinforced music it also is hard not to be snarky. The only thing that really needs adjustment anyhow are the speakers. The rest is time-n-phase correct.

Appolgies for the tone, in any case.

@audition__audio , That different time correct loudspeakers have different tonal balances suggest that your complaint might be the result of something other than time correctness.

Other than the Thiel CS 5 and 5i, I don’t think the other Thiel models cross-overs are that much more extrodinarily complex than some others.

While you are certainly entitled to your opinion and indeed many other’s share it too, the Thiel’s have also been reviewed by others as having something of the opposite impresson. They tend to measure relatively flat.

I suppose if someone in Washington state or Alabama had a set of Thiels then they could be tested on a Klipple.
Then would have something objectively interesting.

@rooze  I wonder if the Evolution Acoustics MM3s which have a family resemblence to Dunlavy Vs have similar time alignment.  Does anyone know?

Despite the truly great sound emanating from Dunlavy's, I cannot tolerate single point/seat listening.  Sure, it's great for me, but not for my wife and my friends who sit across a 10 foot couch.   I am looking at speakers more like Von Schweikert's which have a very broad listening/seating area for tonal equality many feet in width.  My wife hated the Monolith IIIs in 1997 prior to my getting Legacy Focuses and double pair of Hallographs.  

I just think it's amazing I've started a discussion without saying anything is the KING.