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

amirm

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A viewer of my videos and member he suggested that I do a video commenting on a video that Paul McGown did on audibility of phase shifts. Here is Paul's video which was really about a different question (why we need wideband amplifiers) but turned it into phase being an audible problem:


Here is my answer to him:


Of course phase is an important electrical and acoustic thing and has relevance in countless situations. It is just that it should not be used to create myths and fear in audiophiles with respect to audibility in the context Paul and others are using.
 
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johnp98

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Amazing video! Thanks!

I am curious how this applies to high end dsp / digital room corrections. As it seems like Dirac and other high end DRC really stress that they use FIR and IIR filters to help with the phase of each speaker. I get how having symmetrical phase in the L and R speaker is important (just wire one of your speakers out of phase to see the effect). But my understanding is that as long as both speakers have the same phase then its ok and not worth chasing (which this video also agrees with). So is there any utility to high end room correction and their focus on phase? Or what am I missing about DRC when they talk about phase correction?
 

dfuller

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Copying my comment from Youtube: The way I see it, within a channel phase matters very little because speakers are almost all an absolute nightmare in terms of phase. Minimum phase crossovers rotate phase a lot, and unless you really screw it up, it's not audible. Channel to channel phase within the audible band matters somewhat (wouldn't want to be more than a few degrees off between L and R, it'll screw up stereo imaging real good) but within one channel it's pretty inaudible.
 

KSTR

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Amazing video! Thanks!

I am curious how this applies to high end dsp / digital room corrections. As it seems like Dirac and other high end DRC really stress that they use FIR and IIR filters to help with the phase of each speaker. I get how having symmetrical phase in the L and R speaker is important (just wire one of your speakers out of phase to see the effect). But my understanding is that as long as both speakers have the same phase then its ok and not worth chasing (which this video also agrees with). So is there any utility to high end room correction and their focus on phase? Or what am I missing about DRC when they talk about phase correction?
You do that test the other way round. Take a system with proper "full-blown DRC" and resulting smooth FR and flat phase response from each speaker. Then introduce a analytically calculated phase distortion which mimics for example the phase rotations from a typical 3-way passive speaker. This can then be A/B tested (or ABX) and then most people will find that phase distortion is audible and can be detected (once you know what to listen for and have the right music tracks that highlight the effects) but the difference is very subtle, the proverbial icing on the cake. Channel matching of FR and phase is much more important, exactly as you say.
Phase contribution of electronics... forget about it, except for very pathological cases.
 

Frgirard

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Andrew Hon and the phase distortion
start page 51
(page 51 translation)
Unlike older studies, recent studies conclude that the phase distortion is audible.

A very enlightening example

The study by the ABX comparison method conducted by David Clarke in 1981 concluded that the phase distortion was inaudible.

An almost similar study, conducted with the same methodology by Andrew Hon in 2002, comes to the opposite conclusion.


the others pages are in english.

https://www.melaudia.net/zdoc/distorsion_de_phase.pdf
 

PeteL

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Amazing video! Thanks!

I am curious how this applies to high end dsp / digital room corrections. As it seems like Dirac and other high end DRC really stress that they use FIR and IIR filters to help with the phase of each speaker. I get how having symmetrical phase in the L and R speaker is important (just wire one of your speakers out of phase to see the effect). But my understanding is that as long as both speakers have the same phase then its ok and not worth chasing (which this video also agrees with). So is there any utility to high end room correction and their focus on phase? Or what am I missing about DRC when they talk about phase correction?
Yes, that's a bit sad a lot of engineering wasted on FIR?
Also let's say you play a tone at crossover point between your main and your sub, and you move the sub, you can actually clearly measure (and hear it) with a spl meter the amplitude in the room of that played tone go down when out of phase, and increase in volume when there is less cancellation.
Also, to which extent? Low order filters have very gradual phase shift, inaudible, but when you go and have much High Q Notch style filtering, it's quite severe phase shift, I understand reflections, but direct sound is much larger amplitude than reflected sound. I will never be the one to put in doubt the studies, but I'd like to know the scope of it, the limits of the test, cause there are always.
 

ayane

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I can't take PS Audio seriously and I think most people on this forum don't either... Thanks for the debunk =)
 
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Spkrdctr

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That was a great video! Amir got into the sound bouncing around like crazy BEFORE it even gets to the eardrum and then he mentioned how the brain takes over and does whatever it wants to the sound. The problem we have in audio is that the brains activity regarding sound is not consistent, it varies by the hour, the mood, the day, and many other physical attributes. This is why I rant and rave about people looking at EXTREMELY small measurements and thinking they can hear them. The current state of the art in mid fi and hi fi usually sends a pristine signal to the speakers, then the speaker reproduces it with its own coloring, then the room demolishes all that fantastic clean signal and then it hits your eardrums and the brain takes over and does whatever it wants to the sound you perceive (all kinds of biases). As Amir said, you will never hear phase shift and I would even say at normal listening distance 10 feet? you may not hear any time alignment either. Some speakers try to time align while most others do nothing about it. Now how about fairly low levels of distortion? Probably not worth mentioning. The current state of music reproduction has passed the sensitivity of our ears by a country mile. That is why it is so important to do the big three, speaker placement, room EQ and room treatment. That is the low hanging fruit that must be addressed before spending any real money on amps, pre-pro and other stuff. Amir knocked this video out of the park and hit on all the hot topics. I hope the audience understands the gems that Amir dropped all through the video. Good Stuff!
 
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amirm

amirm

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the others pages are in english.
What other pages? I only found a couple which made assertions. The rest is not. Do you want to translate the bits you want us to pay attention to?
 
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amirm

amirm

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Amazing video! Thanks!

I am curious how this applies to high end dsp / digital room corrections. As it seems like Dirac and other high end DRC really stress that they use FIR and IIR filters to help with the phase of each speaker. I get how having symmetrical phase in the L and R speaker is important (just wire one of your speakers out of phase to see the effect). But my understanding is that as long as both speakers have the same phase then its ok and not worth chasing (which this video also agrees with). So is there any utility to high end room correction and their focus on phase? Or what am I missing about DRC when they talk about phase correction?
I responded in youtube to the same question:

"Unfortunately they do a lot to confuse this issue. In reality, "phase" is not what matters there. What matters is the complexity of the filter needed for the correction. In low frequencies you need a very high precision filter that is accurate to 1 Hz and below. Such filter if built using FIR method, is computationally very expensive and becomes specially so in multi-channel AV processors and receivers. So they take a shortcut and use a different type of filter called IIR. IIR is recursive so very efficient and cheap to implement. But creates phase distortion which as I have explained, is not an audible concern. "
 

JoostE

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Is there an exception to this in bass? I try to correct for phase in the higher frequencies in my home made speakers, but you might be right and it might not matter, the differences are very small. However, in the bass, it is very very clear. In phase and out of phase makes a measurable difference in dB. Ever set up a subwoofer with a phase setting?
 

audio2design

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Andrew Hon and the phase distortion
start page 51
(page 51 translation)
Unlike older studies, recent studies conclude that the phase distortion is audible.

A very enlightening example

The study by the ABX comparison method conducted by David Clarke in 1981 concluded that the phase distortion was inaudible.

An almost similar study, conducted with the same methodology by Andrew Hon in 2002, comes to the opposite conclusion.


the others pages are in english.

https://www.melaudia.net/zdoc/distorsion_de_phase.pdf

Oh come on. Paul, who should be supplying a shovel with each video, is not talking about massive phase shifts that Hon refers to to induce audibility, nor is he talking about differential phase shift (different between channels), nor about phase-shift between elements that induces frequency shift. He is talking about the rather gradual phase shift that occurs at the bottom and top of the frequency range, usually very similarly between each channel.
 

PeteL

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Oh come on. Paul, who should be supplying a shovel with each video, is not talking about massive phase shifts that Hon refers to to induce audibility, nor is he talking about differential phase shift (different between channels), nor about phase-shift between elements that induces frequency shift. He is talking about the rather gradual phase shift that occurs at the bottom and top of the frequency range, usually very similarly between each channel.
But it's not because Paul is not talking about that that it's uninteresting.
 

audio2design

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What other pages? I only found a couple which made assertions. The rest is not. Do you want to translate the bits you want us to pay attention to?

This basically covers the same stuff. https://www.melaudia.net/zdoc/jml_crossovers_etf04.pdf

See my comments above w.r.t. applicability. This paper in itself has some specious claims, ignores the filter/phase properties of the mechanical systems, ....
 

respice finem

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Just a thought: The phase shift/distortion introduced by countless reflexions, in an average listening room, will probably be way above the "sins" of the audio chain. A little "chaos" may not be audible, the sum of it probably will.
But, even if the audio chain could be made absolutely perfect, it wouldn't help too much in that average room.

Ceterum censeo: treating the room beats reasoning about audibility in ideal conditions.
 

q3cpma

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Time to post the usual suspect: Audibility of Loudspeaker Group-Delay Characteristics

Loudspeaker impulse responses were studied using a paired-comparison listening test to learn about the audibility of the loudspeaker group-delay characteristics. Several modeled and six measured loudspeakers were included in this study. The impulse responses and their time-reversed versions were used in order to maximize the change in the temporal structure and group delay without affecting the magnitude spectrum, and the subjects were asked whether they could hear a difference. Additionally, the same impulse responses were compared after convolving them with a pink impulse, defined in this paper, which causes a low-frequency emphasis. The results give an idea of how much the group delay of a loudspeaker system can vary so that it is unlikely to cause audible effects in sound reproduction. Our results suggest that when the group delay in the frequency range from 300 Hz to 1 kHz is below 1.0 ms, it is inaudible. With low-frequency emphasis the group delay variations can be heard more easily.
 
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