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


Some designers strive for phase and time coherency.  Will it improve sound quality?

jeffvegas

If one defines fidelity as when the output of the acoustical waveform matches what the signal is... Then it seems like it cannot happen to be correct until the time and phase response is correct. All things being equal, it will will not hurt.

A lot of people believe that we hear in the frequency domain. It is certainly easier to describe a system’ s frequency response in the frequency domain.

it is also also easy to describe a "system response" using the transcient response.

But a lot of scientific work suggests that in reflective spaces, Phase is not the primary issue.

Maybe swap your red and black wire on both the left and right speakers and test whether it sounds any different when the signal is reversed in phase... (some people easily hear it and some people do not.)

One on a very long list of things that make a better loudspeaker. The ones I have now are light years better than the previous ones, even though they were beautifully and conspicuously time-aligned and the better ones equally obviously are not.

some people are essentially deaf to it. Move on if it doesn't float your boat. My favorite Strad player " gets it ". So do I.

there is a big difference between absolute phase and time and phase correct, but IF you can't hear absolute, move right along....

Absolute phase gets thrown out the window with multi-track pop/rock recordings. 

Not being time and phase correct does not eliminate a speaker for me. A time and phase correct speaker has a "rightness", for lack of a better term, that a speaker that is not time and phase correct does not have IME. The negative that I have seen with them is that many of them will suffer dynamic compression when pushed hard. It is a trade off and depends on listening habits and what one truly values. As stated above, some either don't hear it or don't place that much value in that particular trait. To each their own.

Time Aligned, My personal Experience: YES. Size of listening space and distance effect the importance.

Absolute Phase, makes sense that it does, I just have not paid attention to Absolute Phase personally. I suspect if I did, absolute phase will produce increased distinctness. Slightly out of phase is a technique engineers use when mixing to diffuse, widen  .......

Distinctness (not brightness) is very important, it more accurately reveals what the artists and engineers released. It is the primary improvement achieved by my newly acquired CD Player

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Time-Aligned Signal PRIOR to amplification: then Maintain that with time Aligned Speakers

My conclusion while searching for a CD Player with a preferred sound(not everyone's preferred is better) is:

DAC = Salad. Combo of stable dots, then Dual Time Aligned DAC's, then the addittives of sampling, anti-jitter, re-clock, proprietary filters ... can yeild a perceptible difference, for me it is 'distinctness'

which starts out as a small difference, but when applied to everything happening, the drummer's brush work, primary singer, primary instruments, back-up singer(s), improved awareness of an instrument, imaging, each piano note. Repeat, not brightness, not glass precision, but a slight veil removed to hear the distinctness the artists and engineers intended.

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My Time Aligned Speakers

AR2x, my first 'decent' speakers when 18 years old, ollege days, listening to the Nightbird (Alison Steele) and Cousin Brucie late nearly every night,AR2x, sounded better when slanted slightly. 

JSE Infinite Slope Model 2's, Time Aligned Sloped Front, and the patented infinite slope crossover, are the most accurate speakers I own. My son has them now.

My Current Speakers, 15" woofers, horn mid and horn tweeters: preferred sound, (less measured frequency distribution accuracy than the JSE's), sound better after I added a 1-1/2" block within the base to raise the front/tilt them back to:

1. achieve time alignment (not measured), simply approximately achieved based on observations of the angle of other time aligned speakers I have seen and heard.

2. aim tweeters 'up' to direct received sound to seated ear height

3. change the angle of reflections of the larger drivers off the floor/ceiling, as well as toe-in alters the side wall reflections. I recently refined my toe-in with a sound meter, a small change yeilded 

IOW, sloped fronts for Time Alignment improvements are multiple.

Almost twelve years ago when I purchased my current set of speakers even my family could hear the difference.

"Rightness." Why not? I don’t know what to call it in audio speak. After years on the audio merry-go-round the first word out of my mouth was BINGO! It had taken me years to simply understand what was missing.

Laughingly unexpected is how quickly and easy it is to hear designs that are lacking.

 

Your KING OF SUBWOOFER thread sure got ’em bouncing off the walls. I'm not seeing it, did it get pulled?

Angling back the front baffle of the enclosure usually isn't enough, in and of itself, to achieve the desired results.

One of dozens of variables that can be used to build good speaker... undoubtedly doing this has a negative effect on something else. Audio design is all about trade offs. 

One of dozens of variables that can be used to build good speaker... undoubtedly doing this has a negative effect on something else. Audio design is all about trade offs.

Well said. I think with the improvement in driver technology and materials the compromises of 1st-order crossovers has been largely mitigated, but there are always trade-offs. I had Thiel CS1.6es in my system for a while, and I do think there is a certain “rightness” about a well-implemented time/phase coherent design, but that said I hear a lot of the same properties from the likes of Joseph Audio so pick your flavor. All else being equal, which is NEVER the case, I’d take time and phase coherency, but only IF the rest of the sound profile meets with my overall tastes.

OP

Caps lock key broken?

Angeling the speakers back reduces 1st reflection problems, ....it isn't time aligned

Listen for yourself.

I'm afraid that while much is made of it, I've heard time aligned and non time aligned systems and... MEH!

For me it's not the convincing superioiur sound experience the vendor's claim, and acousticians I trust say the same.

That's not to say there are not some very excellent time aligned speakers.  The top of the line Vandersteen come to mind.

Certainly it makes for better sound staging and imaging.

...however, there are varying degrees of what the industry describes, for example, as "time alignment" out there. It can sometimes strike me as more of just a marketing thing...as though either the makers think that at least half the buyers don't really understand what a proper time alignment can attain...or that half the makers don't understand it...or both maybe, IDK. 

Everybody has their own way of making and selling speakers, or choosing them FTM. But IME when you technically do this topic justice, you do get some pretty good rewards.

Eric - yes and as you no doubt aware, there are lots of other fundamental design principles at work; pistonic drivers, matching of drivers to within .25 db, testing the assembly in aneochic chamber against the reference, cabinet within a cabinat, high pass filtered midbass and up, same transfer function for main amp as sub amp, 11 bands of EQ below 120 hz for best image placement vs eliminate bass issues and live w image....the list goes on, since 1977

Not for everyone 

This is what some DIYers are saying  might affect my new dual FR design speakers,, that running a  pair of FR, one FR might be slightly nearer my listening field and thus reaches my ear BEFORE the other FR,, this a  bunch of muddled fq's. 

I say not so.

I've experiemented with this Duo design and had no issues with time/p incoherency.

 

Its all a  myth. 

Sure if you have 1 driver 1 foot behind the other,, the its possible, but all drivers at same distance, there is no such thing as 1 driver faster than the other due to one milli second slower/faster vs the other driver.... thus distortion,, its all baloney.

, matching of drivers to within .25 db ~~~~~~~~~~~~~~~~~~~~~~~~ All my drivers are completely dif sensitivity. 87, 91, 95 and about to add a 93. Sounds wonderful.
I'm afraid that while much is made of it ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Yep,

Jason excellent point which is why i don't use or advocate modern multi track recordings as a reference. Cat will chase own tail using those......

2 or 3 microphones please....

All the rage back in the early 80s. Until everyone discovered that it was marketing nonsense.

I only noticed time alignment issues with present highly modded Klipschorns when in stock form. Originally mid driver and tweeter mounted on same baffle, mid driver sat probably 17" behind tweeter, this due to long exponential horn on mids. My mods replaced stock horn with Volti tractrix and tweeter mounted on separate baffle. I've mounted tweeter baffle essentially in line with mid driver. In stock form Klipschorns and some other Klipsch perceived as bright, certainly true with mine in stock form. Better time alignment has meant better tonal balance, no more of that beaming high and mid high freq., also far superior imaging, sound staging. But then, this was extreme example of poor time alignment.

My Merlin VSM-MM never had perceptual time alignment issues. Having said that, I did run Omega single drivers  with 2a3 at one time, coherence was really something special, even compared to Merlins, a two way which have rep as  being very coherent.

 

As for phase, I recall seeing a website some years ago where someone measured and listed cd's recorded in proper and reversed phase, turned out recordings pretty random here, reason for phase switches on many dacs.

Professional speaker management systems at the top of the scale in performance all have adjustments for time alignment. When you start talking about several stacks of drivers it starts getting a bit more complicated. There is a masters level course in the subject at one ot the TX universities, professor wrote a text on the subject. I got the books somewhere can not remember the professors name.

If you setup a speaker system in a anechoic chamber you can definitely hear the change with changes in timing if you are sensitive to the issue. The crossover points seem to be noticed by most people even in the a good listening room. To me it just sounds noisy at the crossover points.

I am working out a design for amps and such a management system on a budget. If interested check out "mini DSP", they have off the shelf solutions that are not too expensive. The DSP chips they use would be a good place to start a study of the issue, easy to work with.

I like the idea that the system could be used to make a system with a series of appropriately placed divers and apply a spread spectrum digitization of someone talking and aim the system at particular person in a crowd and that person would be the only person that would hear the person talking everyone else will only hear noise. Nice toy for spies. There is a patent on such a system.

So yes, it makes a difference.

It can but speaker designers who use computer models are getting very close.  That being said and owning Vandersteen 5As, just because these speakers are does not mean that they always sound fantastic.  There is more to making a system sound fantastic then the speaker.

 

Happy Listening.

Using DSP  a linear phase perfect impulse response can be done and is in certain active speakers. 

If I have to pick the most important factor in sounding live it's linearity. Double the input then the output should double. Triple and etc. And it's true in the entire system, not just speakers. I recall Bud Fried's speakers were linear phase and roughly time aligned but it was their linear changes in sound pressure level that made the sound real. And There are non linear phase and non time aligned speakers that sound real like ATCs and again it's linearity that makes it happen.

If I have to pick the most important factor in sounding live it's linearity. Double the input then the output should double. Triple and etc. And it's true in the entire system, not just speakers. I recall Bud Fried's speakers were linear phase and roughly time aligned but it was their linear changes in sound pressure level that made the sound real. And There are non linear phase and non time aligned speakers that sound real like ATCs and again it's linearity that makes it happen.

Why stop there? (one should be able to rank them maybe using Floyd's book)
But I think I agree with you, as non linear systems have a lot of harmonic distortion and IMD.


We can talk about the frequency response as the thing the translates best statistically to "being perceived as being good".

So if one had a speaker that was not time/phase correct, but had good frequency response, no cabinet resonances, and a good pattern, then they would sound better than a time/phase aligned speaker with bad FR.

If one uses a DSP to make the FR good, then we get a different fight.
If one uses a different DSP to also do impulse response (phase) EQ, then it is different again.

However a DSP cannot remove cabinet resonances , harmonic distortion, IMD, and port noise, and compression.
If you got ^those^ good however, one could do the rest in the specific few DSPs that allow it.

I'm sure I'm biased because I have Thiel CS 3.5's, but, even though they are voiced differently, I find that Thiels and Vandersteens (and Maggies) just sound right compared to so many otherwise good speakers. I'm not sure, but I believe the phase and time coherence make a big difference, at least to me!

Using vandersteen speakers. They are a pain in placement. But when you got it right the time aligent/phase coherent design is gorgeous. About 5 years go i measured/corrected them (for most my horrible Room acoustics) with Mathaudio Room EQ (incombination with Foobar 2000 for free) sound wise, it Raised them to another higher level esspecialy in imaging which they already did well. In 45 years time investing in a measuring mic of less than 100,- euro is the best audio investment i did in 45 years time.

the powered KEF 50 use DSP to correct the passive KEF 50 impulse response...somebody at KEF thought that a worthwhile thing to invest effort into....hmmmmmmmmm....

 

Ever hear a group of unamplified musicians playing spread apart on a stage...anywhere? No phase or time allignment occurs. Hmmm...

Ever hear a group of unamplified musicians playing spread apart on a stage...anywhere? No phase or time allignment occurs. Hmmm...

Not true...
For instance, say a single French horn player is playing a note that has the fundamental in the woofer, and harmonics in the midrange, and even higher harmonics in the tweeter.

Do you want those harmonics to all be related to each other?

Or do you want the midrange to have the phase flipped?

the powered KEF 50 use DSP to correct the passive KEF 50 impulse response...somebody at KEF thought that a worthwhile thing to invest effort into....hmmmmmmmmm....

All the DIRAC like systems doing phase and time correction make for a largely time and phase coherent system.

I suppose DIRAC would not exist, outside of the physics and math useage, if the majority of speakers had nice impulse response right out of the box?

What's the deal with the usage of " time and phase" ? Aren't they the same thing or I'm thinking of the wrong thing being discussed. Anyway with the Dutch and Dutch 8c there is a linear phase mode and a reduced latency mode which turns off the former. Outside of a heavily treated monitoring room or anechoic chamber you won't hear a difference, even then it's very subtle. 

A simple experiment can be conducted to testify if the time alignment affects anything audible. Take a pair of speakers that you think have a good image, tilt the front panel back and take a serious listening again to see if the imaging gets thrown off. Conduct the blind test with the help from the 2nd person if necessary to eliminate any gussing game or mental effect. To me, I need to admit I could not hear any difference. However, at the same toeing angle, tilting them back does change the soundstage slightly.

Every speaker manufacturer needs a hook, a set of claims to sell speakers. Nothing new. 

Dutch and Dutch 8c are coaxial,  their measurements speak for themselves one of the best on axis and off. Linear phase,  constant directivity from 100hz >. 

Maybe we can get this thread removed too if we get him excited?

Can any of you change the group delay on any part of your loudspeaker system from the listening position? Can any of you change absolute phase from your listening position?

I can and these are my observations. I can not hear any difference at all changing absolute phase. Both directions sound absolutely the same. I should also add that my entire system is balanced. I have Three drivers on each channel. The main speakers are one way ESLs. Then there are the subwoofers, two on each channel. The critical timing is between the subwoofers and the ESLs. I can delay either. Once you get into 5 ms delay or more deterioration in bass impact and definition becomes obvious. What you hear depends on the crossover point and slopes. You can see the group delays with a measurement microphone. The only way you can adjust them is with digital signal processing or moving loudspeakers. This is a problem for subwoofers because they work besy only in certain locations, in corners and up against walls. Being able to put the speakers where they work best and deal with the delays digitally is a large advantage. There are many processors on the market that will do this and some are very reasonably priced. 

Mijo like a said 11 bands of Analog eq below 120..... in each speaker Quattro and above, admittedly not everyone's cup of tea, java, pinot, etc.....

Wolf if time and phase don't matter, how is it your ears or the Decca tree  ( substitute in your favorite semi religious cult microphone array choice ) can discern the placement of those musicians on the stage ?

IF the answer is subtle differences in frequency response aka loudness, then matching drivers down to .25 db makes sense...

just my $1.50 , two cents adjusted for inflation...

I've owned Dunlavy SC-IIIs for about 3 years now and a key feature of their design is time/phase coherency.

I've tried a number of different speakers over the past 3 years but keep coming back to the Dunlavys. Whether or not it's the time/phase feature of their design that appeals to me over everything else, I cannot say.

Speakers which have come and gone in the last 3 years include Quad ESL57s, Merlin Music VSM BME, Sonus Faber Cremona Auditor M, Dali Mentor 6, Klipsch Heresy, Klipsch Khorns, Tyler Acoustic D2, and I'm sure a couple of others that escape me right now.

I just sold the Klipshorns this weekend and the Dunlavys are back in their rightful place.

I think my next adventure will be to try a set of the PureAudioProject speakers with a horn driver. Anyone have any thoughts on the PAP?

I think the new Grandinote Mach speakers are the best speakers on the market 

Ahh, John Dunlavy. What an amazing speaker designer. RIP.  loved selling his SC IV's and V's back in the day. One of the best loudspeakers I've ever heard.

I have a pair of Thiel CS6 speakers for which time and phase coherence were prime design considerations. This was Jim Thiel's raison d' etre. The CS6 even had the tweeter in the center of the midrange cone to maximize the coherence of the speaker.

As for sound, I went to the 2018 AXPONA and was pleasantly surprised that my speakers and system holds up to pretty much anything I heard that cost less than 6 figures. I think my speakers sound very good for a variety of design reasons but the time and phase coherence have a significant effect.

As mentioned in previous posts there is a tradeoff for any design philosophy and in the case of Thiel speakers it was the need for high current amplification. My speakers have low sensitivity combined with a brutal impedance curve. I run them with a Krell KSA 300S amp that will put out 2400 watts @ 1 ohm and weighs 185 lbs. If you like tube amps you are pretty much SOL.

I've heard lots of good sounding speakers that didn't have time and phase coherency as a primary design goal but I think this characteristic improves imaging to some degree. The imaging in my system is almost scary. On some recordings I feel like I can reach out and touch the singer or particular instruments and the depth of the image is holographic.

Every speaker manufacturer has their "thing" that defines their unique selling proposition. For Thiel (and Vandersteen) time and phase coherency is their marketing hook but in both cases their designers combined a range of good practices to make their speakers sound great.

I agree with 8th-note.  I have the Thiel CS6 speakers too.   On some recordings I feel like I could get the singer's autograph.  The top Vandersteens are the only other speaker I have heard that does that and sounds a bit better.  All it takes is money.

I suspect Mr Vegas is a reincarnation of another fellow we all 

know and miss. Not.

I well-remember the magic of listening to Dunlavy's in Colorado Springs years ago in The Sound Shop, at a friend's home with IVs, and listening with John Dunlavy and meeting him (a wild guy) in his CS facility. They were very special but a tiny magic zone. For generally superb musical quality but one-person listening, they might get on my list.

As for knowing if I can really hear time and phase coherency, I'm not real sure of my ears unless someone told me what to listen for. I might be able to with a bit of learning.

I do know I am very sensitive to frequency adjustments and much prefer the sound of a room that is bass-corrected and very minimally DSP processed to yield a flat frquency curve with care to time and frequency. A 'repaired' room always sounds cleaner and better defined with no loss of bass intended to be there originally.

 

For Thiel (and Vandersteen) time and phase coherency is their marketing hook but in both cases their designers combined a range of good practices to make their speakers sound great.

He list I heard was: Dunlavy, Quad, Spika, Thiel, Vandersteen

And we pretty much have the majority of posters here talking about their T/P aligned speakers.

https://www.stereophile.com/content/measuring-loudspeakers-part-two-page-3