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

Francis Vaughan

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I have no idea why you appear to be railing against maintaning absolute polarity in a reproduction system.
I just don’t think it matters. Prior to CD nobody had any clue about absolute polarity. There remains scant evidence it matters either. There have been proper studies that suggest it doesn’t matter. The assumption that the recording chain did anything at all to maintain absolute polarity is not well supported.
But it starts to take on a life of its own. Unless you check every recording for its recorded phase before playing it, and swap phase to match, you don’t believe in it either.
I’m particularly grumpy today. So that has a bit to do with it.
 
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I will. However the problem is that you are not necessarily validating proof of audibility of absolute phase. You may be validating that your reproduction chain has an asymmetric transfer function. Lots of speakers and headphones can. You need to show that whatever distortion your system has it is not overly asymmetric in nature. Even harmonic distortion is a good start to such behaviour.
This is why I prefer a peer reviewed study. Whist your double blind trial is good, unless you validate your test system, it remains anecdotal.
I've passed that ABX test with every combination of DAC/amp/headphone/speaker I've tried (using various transducer technology i.e. dynamic driver, planar magnetic, electrostatic, balanced armature), several of which have been measured here and elsewhere as being audibly transparent. Anyhow, even if it turns out the difference I hear is partly due to distortion, the other jointly sufficient cause is still polarity, so this still shows the latter is important in practice as it has caused audible issues in a variety of playback equipment, and so does indeed matter for audio reproduction.
 
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Thanks for the tips! I may try again...
Though, I will say again that "obvious" seems like a hyperbolic description, imo.
The test felt like another one of those, "if you have to squint to see it" effects...
Well I said "pretty obvious to me", which I don't think is hyperbole considering I can pretty easily get 10/10 correct in an ABX test. It may be less (or even more) obvious to others depending on their hearing, listening / ABX experience etc.
 

markus

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There might be other elements, but what was immediately apparent to me and what I listened for in the ABX test was the (possibly percussive) low bass sound within the first couple of seconds (maybe a hand or string striking the fretboard or guitar body?). This sound was more prominent in the inverted version, but also kind of more diffuse sounding - difficult to describe, but easy to hear. I'm curious, can anyone else hear this and successfully pass the ABX test I linked?
Took the test at https://www.audiocheck.net/blindtests_abspolarity.php and failed. At the beginning I could reliably detect a difference but then it was just guessing. The test was very casual though. Will repeat when time permits.

I did the test before you answered and did also focus on the low frequency "oomph" at the beginning and the end as it was the only difference I could spot between the original and the polarity inverted version.
 
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The assumption that the recording chain did anything at all to maintain absolute polarity is not well supported.
Regardless of what the recording chain maintained or not, I would certainly like to listen to the same phase as the mastering engineer did, even if he got it wrong. From there, it would be quite easy to maintain the phase, and even if I wouldn't hear any difference, it doesn't cost anything either.
 

thewas

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As an explanation attempt why not everyone seems to hear them, maybe some audio devices like transducers and/or (damaged?) ears introduce some extra asymmetric non-linearities which make them (more) audible?
 
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In my Kef Ref 201/2s the woofer has reverse acoustic polarity to the tweeter and mid range unit so how do you handle that? I don't think it's the only speaker that does this kind of thing.

Regards Andrew
 

KSTR

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Do you have a modern citation? Genuinely interested. Peer reviewed modern research. And, no I'm afraid a personal anecdote doesn't count.
It has been a while since I looked into this, and if there is more modern work showing this I'd be interested.
This is the answer I've expected.
You want to be spoon-feed with evidence and are not even willing to do you homework first:
- do you own (internet) search on the topic.
- do some informal listening to find out if you feel "there is something to it".
- then conduct your own conclusive tests. ABX'ing polarity flip properly is probably the most easy thing on earth in this regard.

Many many moons back I had the same type of mindset: I'm lazy bum, so you show me proper top-class scientific evidence or else I'm not going to believe because I don't want to believe (correcting one's beliefs is never easy) and because I'm lazy. That's a very comfortable dead-lock. You have to get out of your comfort zone, dude! Once I did, things opened up.

Sadly, I see this mindset more and more often on this forum and it annoys me big time.
 

thewas

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In my Kef Ref 201/2s the woofer has reverse acoustic polarity to the tweeter and mid range unit so how do you handle that? I don't think it's the only speaker that does this kind of thing.
Usually the polarity of the tweeter is accounted for that as its supposed to be dominant in the pulse/transient behaviour.
 

ctrl

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For all of you who can't handle the absolute polarity test on the Audiocheck website (like me), here are the audio files for download and use in the foobar ABX-comparator. Have analyzed the two files, the frequency responses are identical - so only the phase frequency responses are different.

After picking a short two second spot, I had 14/16 on the first pass.
The result of the second pass was 16/16:
1623403074448.png


Once you know what to look for, it's not hard.

However, if someone were to play me two pieces of music in a row, one with inverse polarity, I would probably not notice the difference.

Now I am also discussing things that have nothing to do with the original question (amplifier FR roll-off and phase shift) :mad: - I have to ask my therapist what that means ;)
 

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Did you do the test on speakers or headphones?
I think this is the key question here. Even the 'older' papers by Toole et al. state phase change is audible, but subtle and was noticed while using headphones or in anechoic chamber. Nothing really new right?
Getting the feeling some here are talking about speakers in normal reflective rooms VS ABX performed using headphones.
In the former it's not (that) audible, apart from cancellation dips in (Sub) crossover region when misaligned. In the latter it's audible when you know what to listen for...as some have already shown with their ABX results.
 
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Audible or not doing a quick Google showed that phase changes are being deliberately made/researched for digital water marking.

In addition to audibility when doing AB testing is one prefered to the other?
Regards Andrew
 

ctrl

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Thomas_A

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KSTRs example was quite easy to hear on my loudspeakers as well, in a living room. However i suspect my audio chain has flipped polarity. :) Not 100 sure how a correct one should sound like but the guitar which correct polarity in Audacity sounded more aggressive with higher timbral content and the flipped one more dark and fuller. I prefer the dark and fuller one.
 
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Robbo99999

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This is the answer I've expected.
You want to be spoon-feed with evidence and are not even willing to do you homework first:
- do you own (internet) search on the topic.
- do some informal listening to find out if you feel "there is something to it".
- then conduct your own conclusive tests. ABX'ing polarity flip properly is probably the most easy thing on earth in this regard.

Many many moons back I had the same type of mindset: I'm lazy bum, so you show me proper top-class scientific evidence or else I'm not going to believe because I don't want to believe (correcting one's beliefs is never easy) and because I'm lazy. That's a very comfortable dead-lock. You have to get out of your comfort zone, dude! Once I did, things opened up.

Sadly, I see this mindset more and more often on this forum and it annoys me big time.
(You could just show him the link to the study to support your argument & to educate people, it's not really a big deal is it.)
 
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Interesting that it's the base and thanks for the info. Regards Andrew
This may be the dumbest thing I have ever written, but bear with me and call me stupid if this is as I am working it out in my head ..... :)

If you invert the polarity, could that cause a temporal shift in room nodes, at least w.r.t. other frequencies, making the audibility a factor of room modes? .... then again, if could just be that woofers have higher linearity variation w.r.t. movement direction.
 
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I think this is the key question here. Even the 'older' papers by Toole et al. state phase change is audible, but subtle and was noticed while using headphones or in anechoic chamber. Nothing really new right?
Getting the feeling some here are talking about speakers in normal reflective rooms VS ABX performed using headphones.
In the former it's not (that) audible, apart from cancellation dips in (Sub) crossover region when misaligned. In the latter it's audible when you know what to listen for...as some have already shown with their ABX results.
Looks like you missed this post of mine:
Initially headphones, just tested with speakers and also got 10/10 correct (I do have a 2.1 system with the sub pretty close to my seating position, maybe that's a relevant factor). So this issue is not only detectable with headphones as is often claimed.
 

KSTR

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(You could just show him the link to the study to support your argument & to educate people, it's not really a big deal is it.)
As a starter, go here: http://www.silcom.com/~aludwig/Phase_audibility.htm
That polarity inversion / phase shift is generally audible really is a knowledge many decades old. In the Lipshitz paper from 1982 Lipshitz states "Some of these effects have been known for over 30 years, and are quite audible on even very simple signals."
It really escapes me we are still discussing this, the issue is settled once and for all and therefore any further research won't happen.
 
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