Does Phase Distortion/Shift Matter in Audio? (no*)

[j_j]

Take any music track of your choice.
Calculate its frequency spectrum.
Reverse the music track.
Calculate the frequency spectrum of the reversed track.
You will find that both spectra are identical.
But the music sounds different for sure

Yep.

There's also this, of course, the actual data is no longer available, but it's easy to recreate such results.

AES E-Library » Testing Loudness Models—Real vs. Artificial Content

A variety of loudness models have been recently proposed and tested by various means. In this paper, some basic properties of loudness are examined, and a set of artificial signals are designed to test the 'loudness space' based on principles dating back to Harvey Fletcher, or arguably to Wegel...

www.aes.org

Of course, putting your music through the following filter:

Numerator .3 Z^5 +1
Denominator 1 + .3 Z^5 Note, using MATLAB ordering and polarity

(Hint: This is a pure allpass filter, no, it's not minimum phase, of course.)

Tell me that sounds 'normal'.

Yes, phase matters.

This doesn't include the "does phase matter in the bass" question.

Take a headphone, put 50Hz into both channels. Then, say, 5 degrees at a time, change (delay, advance, doesn't matter) the tone into one channel.
Keep the level down so you aren't listening to harmonics.
Just try it.
Yeah, phase matters.

Y'all have a nice day.

 

[youngho]

Yes, phase matters.

This doesn't include the "does phase matter in the bass" question.

@j_j , if the middle ear has a first-order high-pass filter at around 700 Hz, would this filter introduce phase shift on the perception end, and if so, what would that mean on the reproduction end regarding phase of content below 700 Hz relative to content above 700 Hz? Sorry if this is a naive or poorly phrased question.

 

[j_j]

And it is hard to mathematically compare the measured sound against the electrical signal when the phase is flipped…
One sort of needs to use only the magnitude, if they want to ignore the phase.

Hardly. One analyzes both, and points out the phase flip.

Maybe a trip through the Heyser papers is called for here.
You just need to RECOGNIZE the way the information appears.

Let me ask you a question here: Can the signal I'm about to plot here be used to get subsample delay measurements?

 

[j_j]

@j_j , if the middle ear has a first-order high-pass filter at around 700 Hz, would this filter introduce phase shift on the perception end, and if so, what would that mean on the reproduction end regarding phase of content below 700 Hz relative to content above 700 Hz? Sorry if this is a naive or poorly phrased question.

It's a good question. The answer ***APPEARS*** to be that for interaural phase it (eardrum hp filter) doesn't matter (yes, you adapt to your personal situation) and for intraaural, some part of your CNS copes with this.

Note: Appears...

But in short, you adapt for your own HRTF's and mechanics amazingly well, even when they vary over time.

 

[Holmz]

Hardly. One analyzes both, and points out the phase flip.

Maybe a trip through the Heyser papers is called for here.
You just need to RECOGNIZE the way the information appears.

I was not able to find anything under a quick google of Heyser.
do you have a link?

Let me ask you a question here: Can the signal I'm about to plot here be used to get subsample delay measurements?

View attachment 346887

I would generally upsample… or if there are two copies of the same signal, then I would look at cross spectral phase.
so I think one can get sub sample delays, but I would not bet on it.

 

[youngho]

I was not able to find anything under a quick google of Heyser.
do you have a link?

There was someone important in the field named Richard Heyser. You could get a sense of some of his contributions here: https://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf

 

[j_j]

There was someone important in the field named Richard Heyser. You could get a sense of some of his contributions here: https://www.aes.org/technical/documents/openaccess/AES_TimeDelaySpectrometry.pdf

I was not able to find anything under a quick google of Heyser.
do you have a link?



I would generally upsample… or if there are two copies of the same signal, then I would look at cross spectral phase.
so I think one can get sub sample delays, but I would not bet on it.

Yeah, so another look at that old FFT deck I pointed to a while ago, maybe?

 

[gnarly]

https://www.aes-media.org/sections/pnw/ppt/jj/filtutv1.ppt might also be useful here.

Great paper. Thank You !

 

[Snarfie]

Don't know in how far phase shifts could be audible if corrected bij software like Dirac Mathaudio etc. I got now in 50 years quite some speakers. Regarding column speaker around 4 aprox 1 meter high with some forward an backward firing bass ports. Al more ore less same anomalies regarding FR.

When i finally got my current Vandersteen speakers at the best spot tillted them as described in the manual i was astound about there musicality imaging second to none especially when they where corrected with DSP. They are build/designd phase/time alignt.

At the time i still had my other column speakers (also corrected by same DSP) compared them in minutes no competition/comparison regarding imaging listening into the recording as i do with the Vandersteen was not coming close.

So i wonder does phase has something to do with beter revealing imaging listening into a recording.

 

[j_j]

So i wonder does phase has something to do with beter revealing imaging listening into a recording.

Depending on what you define as imaging, between 40-90Hz and at least 1kHz, yeah, in binaural terms, you BET it makes a difference.

The effect in monaural terms is best described "not quite real" for substantial all-pass in that range. Between 1 and 2 kHz you lose a bunch of phase sensitivity, and then you get it back, sort of, by the ear detecting onset of the envelop of the signal in a given ERB. But above 4K, it's mostly onset of the envelop, I'm pretty much convinced. Note that interchannel phase is more sensitive in many ways below 1K.

 

[ernestcarl]

The effect in monaural terms is best described "not quite real" for substantial all-pass in that range.

I don't know how common speakers that have a lot of all-pass phase wraps are, but here's one from Bose:

I've heard this speaker myself and found it quite impressive for its size. The reviewer in this video mentioned that it lacked impact when increasing volume, and it's not just because the drivers are small -- I think. The bass of my dinky little Fostex 6301 sounds significantly more "real" or natural to me despite the early roll-off.

 

[j_j]

I don't know how common speakers that have a lot of all-pass phase wraps are, but here's one from Bose:

View attachment 347649

I've heard this speaker myself and found it quite impressive for its size. The reviewer in this video mentioned that it lacked impact when increasing volume, and it's not just because the drivers are small -- I think. The bass of my dinky little Fostex 6301 sounds significantly more "real" or natural to me despite the early roll-off.

What you're seeing there is the granddaddy of electronic compensation for a low frequency system.

 

[Snarfie]

Depending on what you define as imaging, between 40-90Hz and at least 1kHz, yeah, in binaural terms, you BET it makes a difference.

The effect in monaural terms is best described "not quite real" for substantial all-pass in that range. Between 1 and 2 kHz you lose a bunch of phase sensitivity, and then you get it back, sort of, by the ear detecting onset of the envelop of the signal in a given ERB. But above 4K, it's mostly onset of the envelop, I'm pretty much convinced. Note that interchannel phase is more sensitive in many ways below 1K.

With imaging i mean that between voices instruments because of a full room correction i get ride of let say a bit of hiss between them (found in measured FR over an area 400 till 10khz has sometimes an ofset of 14db) . This results in a almost dead silence between voices instruments what have you. This adds to more distance between them hearing better depth. Result in better imaging hearing the reverb /atmosphere of the venue recorded in. When recording is excellent you get a sort of intimate feeling hearing not only the music but a band playing thats my impression. I guess that this has for instance to do with phase/time alignt behaviour. This experience in my specific room i only have with phase/time alignt Vandersteen speakers by build other speakers don't come close. An yes i afcourse did not hear probably speakers that can do the same.
I'm not a audio technical specialists so asking whats going on.

 

[Holmz]

… speakers by build other speakers don't come close. An yes i afcourse did not hear probably speakers that can do the same.
I'm not a audio technical specialists so asking whats going on.

@Snarfie
It is also Duntech/Dunlavy, Spika, Theil, and another speaker that used 1st order crossovers (XOs), and were also time/phase correct.

One usually likes the rest of them, if they like one of them.

The trend has been towards higher order XOs and not phase correct.

 

[Snarfie]

@Snarfie
It is also Duntech/Dunlavy, Spika, Theil, and another speaker that used 1st order crossovers (XOs), and were also time/phase correct.

One usually likes the rest of them, if they like one of them.

The trend has been towards higher order XOs and not phase correct.

Yes do.know Thiel but also planar solutions. Had with a Quad ELS63 for first time Experience with imaging/staging only i found it is missing low experience. To my surprise the Vandies produce a similar sort of planar wide sounds stage but than with laid back low. Specific voice's sounding not boxy probably because it's Minimal bavel build tweeter i presume.

 

[Holmz]

Quad was one of the 5.

 

[dlaloum]

Dunlavy: "And we find that in order to reproduce those sounds with a level of accuracy such that you cannot literally hear any difference between the live and the recorded sound, you have to have a speaker that exhibits almost perfect impulse and step responses. The only way to do that is to time-align the drivers very, very accurately, usually within a matter of a few microseconds, then use a minimum-phase, first-order crossover network and get everything right. And you have to have an on-axis response of better—well better—than ±2dB."

Perfect impulse needs infinite bandwidth, perfect square waves need infinite bandwidth and be able to produce DC.
Neither mics nor speakers have either of these. So whats "almost" perfect?

There are speakers that do achieve this - eg: Quad electrostatics

Also a number of speakers where the tweeter to midrange transition is achieved without a crossover

I've found speakers in these categories have always seemed more real to me.

 

[j_j]

@Snarfie
It is also Duntech/Dunlavy, Spika, Theil, and another speaker that used 1st order crossovers (XOs), and were also time/phase correct.

One usually likes the rest of them, if they like one of them.

The trend has been towards higher order XOs and not phase correct.

One should stick to digital crossovers. First, you can have time/phase correctness with any order. Second, the crossover will be identical to every speaker. That gets rid of the "vocal tear". Third: Really steep filters eliminate limits on driver usage.

 

[IAtaman]

One should stick to digital crossovers. First, you can have time/phase correctness with any order. Second, the crossover will be identical to every speaker. That gets rid of the "vocal tear". Third: Really steep filters eliminate limits on driver usage.

Tri-amping for the win!

 

[sejarzo]

Has anyone here tried to implement the various techniques that Obsessive Compulsive Audiophile has explained (or attempted to) on YouTube? He claims that correcting phase below Schroeder frequency is important and his technique results in a marked increase in clarity, and now proposes that any efforts to do any correction above that are doomed to result in more problems than are solved.

I tried to implement some of his previous techniques and couldn't get them to work. He's a gifted vector math expert, but he tended to make mistakes and/or get off on tangents in his previous videos and hasn't put together a pdf that clearly explains every step in sequence. At the very least his latest iteration is much simpler than his previous efforts, but I have yet to give it a shot.