Speaker time alignment, does it matter?

[QMuse]

This may be fine with pop and rock studio recordings but with recordings which already have an acoustic signature (mostly minimally-mic'ed classical music) the more "interference" from the listening room the less one is able to listen to the cues of the original venue. It is a form of distortion, like when singing in a bathroom or in a church the sound becomes more diffuse / less focused and the imperfections less obvious.

In my opinion it is not that much about difference in music genres but about difference between live and studio recordings. The former of course being much more tricky to get correctly in the room.

I agree that ultimately its all down to personal preference but I don't think it makes sense to criticise tailored frequency response (i.e. BBC dip, etc.) or a pinch of low- even-order harmonic distortion and condone wide-directivity speakers or a more reflective room.

IMO that is a personal preference thing, so whatever rocks your boat is fine.

 

[BenB]

This may be fine with pop and rock studio recordings but with recordings which already have an acoustic signature (mostly minimally-mic'ed classical music) the more "interference" from the listening room the less one is able to listen to the cues of the original venue. It is a form of distortion, like when singing in a bathroom or in a church the sound becomes more diffuse / less focused and the imperfections less obvious.

I agree that ultimately its all down to personal preference but I don't think it makes sense to criticise tailored frequency response (i.e. BBC dip, etc.) or a pinch of low- even-order harmonic distortion and condone wide-directivity speakers or a more reflective room.

Regarding directivity, I agree and disagree. With typical "narrow" directivity speakers pointed at the listener, you will usually reduce sidewall reflections and front wall reflections (compared to an omni-directional speaker which would be very rare since most have something of a 180 degree horn: a front baffle). You will also reduce high-order reflections from the floor and ceiling, but not the first order reflections, because the vertical dispersion usually isn't narrow enough to do that.

However, the sidewall reflections that were reduced can be seen as something of a fix for the inherent unnatural limitations of 2-speaker stereo, that produces no direct sound farther off-center than the placement of the speakers.

In contrast, we don't have good vertical sound localization (ears on the sides of our heads after all). So the inability of 2-speaker stereo to create direct sound that's authentically higher or lower than our speakers isn't much of a perception problem. If we are trying to re-create the sense of a particular space, we can capture those reflections with our mic, and play them back from the speaker, and be satisfied. The same is clearly true for front-wall reflections: capture them, put them in the mix, we don't need to augment them with our rooms.

With this in mind, a wide dispersion speaker is really no less authentic than a typical narrow dispersion speaker. They both light up the floor and ceiling that they don't need to, causing them to impart the sound of your own room rather than that of the recorded space (whether authentic or synthetic). The narrow dispersion speaker is unnatural in its limited soundstage width. The wide dispersion speaker extends the soundstage in a way that's more natural, but doesn't necessarily match the recorded space.

The most natural sounding and authentic speaker may be one that actually reduces floor, ceiling, and front-wall reflections while maintaining wide horizontal dispersion for increased soundstage width. This would be all the more true if mixers/producers could rely on this type of playback when recording/mixing (at least when done for 2-channel stereo playback on speakers).

 

[tuga]

However, the sidewall reflections that were reduced can be seen as something of a fix for the inherent unnatural limitations of 2-speaker stereo, that produces no direct sound farther off-center than the placement of the speakers.

If you are referring to the fact that 2 channel stereo does not produce phantom images farther off-center than the placement of the speakers, why is that unnatural?
You'd have to be sitting very close to the stage for your field of view to be wider than 90° in order to frame the whole orchestra.

 

[RayDunzl]

The narrow dispersion speaker is unnatural in its limited soundstage width.

Who told you that?

 

[QMuse]

Who told you that?

Martin Logan's chief engineer.

 

[BenB]

If you are referring to the fact that 2 channel stereo does not produce phantom images farther off-center than the placement of the speakers, why is that unnatural?
You'd have to be sitting very close to the stage for your field of view to be wider than 90° in order to frame the whole orchestra.

2-Channel stereo set-up is usually described with the speakers as far apart as the distance to the point directly between them. In my quick calculation, that's about 53 degrees of separation. Additionally, even if the stage width is only 75 degrees, you would still get sidewall reflections from the performance space that are wider than that. Personally, I like to sit very close (4th row at my local theater), which provides a lot of direct sound and diminishes the importance of those sidewall reflections in the hall, but which spreads the stage out probably 150 degrees or so.

 

[Frank Dernie]

2-Channel stereo set-up is usually described with the speakers as far apart as the distance to the point directly between them. In my quick calculation, that's about 53 degrees of separation. Additionally, even if the stage width is only 75 degrees, you would still get sidewall reflections from the performance space that are wider than that. Personally, I like to sit very close (4th row at my local theater), which provides a lot of direct sound and diminishes the importance of those sidewall reflections in the hall, but which spreads the stage out probably 150 degrees or so.

Q-sound recordings give a wider soundstage then the width of my speakers in this room, and surprising depth too. Roger Waters' Amused to Death, for example.

 

[BenB]

Q-sound recordings give a wider soundstage then the width of my speakers in this room, and surprising depth too. Roger Waters' Amused to Death, for example.

I'm sure there are implications from this statement that are relevant to the conversation, but without more information about your speakers and room, I don't know what they might be.

 

[RayDunzl]

Q-Sound gives me 180 degree wide soundfield as long as I face forward.

The effect collapses if I "face" the sound to the side (as expected).

"Regular" stereo extends laterally past the speakers when well recorded (phase information, not just pan-pot, in the instrument placement).

 

[Hrodulf]

I participated in a blind test between my Neumann KH310 speakers and a prototype speaker from a local hi-end monitor company.

The KH310, while a highly proficient device, hasn't been designed in a way to do anything with time coherence. Here's a REW sim for this 3-way speaker.

So, it's a 3-way design with LR24 crossovers. As you can see, the 3" dome mid is more of a helper driver.

These drivers on paper give a perfect frequency domain integration which, to be frank, is realized very closely in the real world as well. The phase, however, warps for every crossover point and there's some shift for the low-end roll-off characteristic of a high pass filter. These time domain effects are well visible in the step response graph.

You can see three distinct blips where each of the drivers fire with some delay between each of them. The big question is, are we able to distinguish anything in the roughly 1.5ms space when all of this goes down? Current psychoacoustics says that our brains just sum everything together and it all comes out perfect in the end. The prototype speaker I was trialing my KH310's against had almost the same bandwidth and used a 2-way point source driver array similar to this (which is their older design) -

I was told by their techs that for them an important design goal was phase coherence. So, the step response for the system should've been something like this -

We did some SMAART measurements of both speaker systems and all of the curves essentially matched the sims with some room artifacts present.

So, how did it sound?

The difference between the two systems, despite having essentially flat AFR, was not subtle. The phase coherent speaker was able to produce louder transients, despite both systems being SPL matched. The other stark difference was in soundstage - both systems could portray almost identical apparent width, however the phase coherent system portrayed depth much better and localisation was more distinct, probably due to point source radiation.

After the listening session I had a word with the engineer and he mentioned one thing I haven't heard anywhere else - off-axis phase response or rather - time domain controlled directivity. When we RTA'd the phase coherent setup with SMAART, it was evident that going off-axis there was some tilting of the AFR response, yet phase changes weren't too pronounced.

Needless to say, I sold my KH310's shortly after.

 

[tuga]

PSI Audio's crossover "is made up of several all-pass filters each acting in a specific range of frequency and together obtaining a Compensated Phase Response."

Why is phase compensation so important?

In a multi-way speaker system, the crossover filters as well as the transducers inevitably introduce phase distortion and consequently also variations of group delay.

The group delays are higher in low frequencies than in high frequencies. Theses create a separation in time between the low and high frequencies which typically gives multi-way speakers a “hollow” sound.

In a limited frequency range, an all-pass filter will allow to alter the phase without influencing the amplitude.

The CPR system is made up of several all-pass filters each acting in a specific range of frequency and together obtaining a Compensated Phase Response. This then provides a constant group delay that is kept to the bare minimum through our entirely analogue technology.

Thanks to the CPR system, the placement of sound in the actual sound space is perfectly accurate. Amongst others, this technology allows designing a surround sound systems with different types of PSI Audio speakers whilst maintaining a perfectly accurate phase response.

https://www.psiaudio.swiss/faq-item...uis-euismod-quis-orci-integer-vitae-nisl-non/

 

[QMuse]

I participated in a blind test between my Neumann KH310 speakers and a prototype speaker from a local hi-end monitor company.

The KH310, while a highly proficient device, hasn't been designed in a way to do anything with time coherence. Here's a REW sim for this 3-way speaker.

View attachment 69823

So, it's a 3-way design with LR24 crossovers. As you can see, the 3" dome mid is more of a helper driver.

View attachment 69821

These drivers on paper give a perfect frequency domain integration which, to be frank, is realized very closely in the real world as well. The phase, however, warps for every crossover point and there's some shift for the low-end roll-off characteristic of a high pass filter. These time domain effects are well visible in the step response graph.

View attachment 69822

You can see three distinct blips where each of the drivers fire with some delay between each of them. The big question is, are we able to distinguish anything in the roughly 1.5ms space when all of this goes down? Current psychoacoustics says that our brains just sum everything together and it all comes out perfect in the end. The prototype speaker I was trialing my KH310's against had almost the same bandwidth and used a 2-way point source driver array similar to this (which is their older design) -

View attachment 69828

I was told by their techs that for them an important design goal was phase coherence. So, the step response for the system should've been something like this -

View attachment 69829

We did some SMAART measurements of both speaker systems and all of the curves essentially matched the sims with some room artifacts present.

So, how did it sound?

The difference between the two systems, despite having essentially flat AFR, was not subtle. The phase coherent speaker was able to produce louder transients, despite both systems being SPL matched. The other stark difference was in soundstage - both systems could portray almost identical apparent width, however the phase coherent system portrayed depth much better and localisation was more distinct, probably due to point source radiation.

After the listening session I had a word with the engineer and he mentioned one thing I haven't heard anywhere else - off-axis phase response or rather - time domain controlled directivity. When we RTA'd the phase coherent setup with SMAART, it was evident that going off-axis there was some tilting of the AFR response, yet phase changes weren't too pronounced.

Needless to say, I sold my KH310's shortly after.

I must say I'm sceptical on this as phase correction doesn't affect frequency response so you won't be getting louder transients - frequency response is identical with and without phase correction.

Besides, it is very easy to apply phase correction to KH310 (or any other 3 way speakers) with 2 LR24 crossovers and get perfect step response.

 

[Hrodulf]

I must say I'm sceptical on this as phase correction doesn't affect frequency response so you won't be getting louder transients - frequency response is identical with and without phase correction.

As was I, until I did the listening test. The big question is whether our brains actually can discern between this:

And this:

As you can tell, the phase coherent setup can physically reach 25% higher sound pressure transient due to the fact that the tweeter wavefront rides on the rest and sums properly. I attribute that to the higher perceived loudness on sharp transients. On more sustained signals the loudness difference wasn't that apparent.

Besides, it is very easy to apply phase correction to KH310 (or any other 3 way speakers) with 2 LR24 crossovers and get perfect step response.

I'm skeptical on the benefits of time aligning non-coincident driver systems. PSI and Dutch&Dutch seem to think otherwise.

 

[QMuse]

As was I, until I did the listening test. The big question is whether our brains actually can discern between this:

View attachment 69833

And this:

View attachment 69834

As you can tell, the phase coherent setup can physically reach 25% higher sound pressure transient due to the fact that the tweeter wavefront rides on the rest and sums properly. I attribute that to the higher perceived loudness on sharp transients. On more sustained signals the loudness difference wasn't that apparent.



I'm skeptical on the benefits of time aligning non-coincident driver systems. PSI and Dutch&Dutch seem to think otherwise.

Once again, you won't see any change in FR when you add phase correction to the speaker with passive XO. You cannot justify being sceptical as once you do a proper phase correction you will get a perfect step response, which comes to no surprise as aligining drivers phisically or aligning them via DSP has the same effect. To hear the difference you need a room with very low reflections as each reflected wave will spoil that perfect time alignement as it arrives at slightly different time than direct sound.

 

[Hrodulf]

You cannot justify being sceptical as once you do a proper phase correction you will get a perfect step response, which comes to no surprise as aligining drivers phisically or aligning them via DSP has the same effect.

For a non-point-source system the time alignment will be very space limited.

 

[QMuse]

For a non-point-source system the time alignment will be very space limited.

No, when you time-align speaker with passive XO it is valid throughout the room. And why wouldn't it be - what would cause misalignement in different point of space? Room modes are causing some disturbance in the phase response which are visible in GD graph but not in step response.

Measured from 80cm:

Measured at 4 meters:

 

[thewas]

No, when you time-align speaker with passive XO it is valid throughout the room. And why wouldn't it be - what would cause misalignement in different point of space?

Different distance to the various drivers, but on most loudspeakers as the drivers are horizontally aligned its only a problem for the vertical angles and thus mainly for the floor and ceiling reflected sounds.

 

[QMuse]

Different distance to the various drivers, but on most loudspeakers as the drivers are horizontally aligned its only a problem for the vertical angles and thus mainly for the floor and ceiling reflected sounds.

When looking at step response reflections should be filtered with FDW otherwise you are getting a mess, and that's the same reason why it is hard to hear phase correction in a non-anechoic environment.

Regarding vertical angles, usually the ratio between drivers distance vs distance to LP is large enough for that not to matter. For example, I don't see practically any change in step response when I measure at 4 meters distance at 80cm height (ears height at sitting position) and 180cm height (ears height at standing position).

 

[Deleted member 16502]

I participated in a blind test between my Neumann KH310 speakers and a prototype speaker from a local hi-end monitor company.

The KH310, while a highly proficient device, hasn't been designed in a way to do anything with time coherence. Here's a REW sim for this 3-way speaker.

View attachment 69823

So, it's a 3-way design with LR24 crossovers. As you can see, the 3" dome mid is more of a helper driver.

View attachment 69821

These drivers on paper give a perfect frequency domain integration which, to be frank, is realized very closely in the real world as well. The phase, however, warps for every crossover point and there's some shift for the low-end roll-off characteristic of a high pass filter. These time domain effects are well visible in the step response graph.

View attachment 69822

You can see three distinct blips where each of the drivers fire with some delay between each of them. The big question is, are we able to distinguish anything in the roughly 1.5ms space when all of this goes down? Current psychoacoustics says that our brains just sum everything together and it all comes out perfect in the end. The prototype speaker I was trialing my KH310's against had almost the same bandwidth and used a 2-way point source driver array similar to this (which is their older design) -

View attachment 69828

I was told by their techs that for them an important design goal was phase coherence. So, the step response for the system should've been something like this -

View attachment 69829

We did some SMAART measurements of both speaker systems and all of the curves essentially matched the sims with some room artifacts present.

So, how did it sound?

The difference between the two systems, despite having essentially flat AFR, was not subtle. The phase coherent speaker was able to produce louder transients, despite both systems being SPL matched. The other stark difference was in soundstage - both systems could portray almost identical apparent width, however the phase coherent system portrayed depth much better and localisation was more distinct, probably due to point source radiation.

After the listening session I had a word with the engineer and he mentioned one thing I haven't heard anywhere else - off-axis phase response or rather - time domain controlled directivity. When we RTA'd the phase coherent setup with SMAART, it was evident that going off-axis there was some tilting of the AFR response, yet phase changes weren't too pronounced.

Needless to say, I sold my KH310's shortly after.

I think this cannot be settled until you try with the exact same speaker and blindly have someone turn phase correction on and off. It would be possible with any HEDD speaker for example, since they do phase correction via a VST plugin that you could turn on and off.

 

[maty]

I'm currently sitting dead center between my Genelec 8351Bs. If I add a 1ms time delay to the left speaker (via GLM software), I can hear an extremely obvious difference in soundstage shift and smearing. To my ears, it is not subtle at all and I have no doubt at all I could discern them in a blind test. Is this to be expected, or counter to existing psychoacoustics?

A long time ago I finished adjusting my modified KEF Q100 5.25" coaxial loudspeakers, which I usually hear in the near field on my second system.

The right channel hass assigned a delay of ... 0.12 ms. The left none. I notice the difference. With JRiver MC 64 bits: DSP / PEQ.