Test CD to hear inverted polarity

[I LIKE MUSIC]

The first step is to determine if one call tell the difference.

Then it is a matter of auditory memory as to which one is correct. With electronically generated music, who is to say?

With acoustic music there may be a better chance to pick the correct one if a person is fairly familiar the correct one. Our hearing is not an absolute measuring device.

 

[Chip Chester]

I didn't take the test, but I did look at the site. (I'm on a little eeepc with crappy audio at the moment.)
But let's say for the sake of argument that I can tell just by listening that the signal polarity is correct. (Probably not true for every signal type.)
And then let's say that my speaker's amp is inverting, (but the rest of the chain is correct) so all correct signals come out incorrect, and vice-versa. But I don't know it.
So I would choose 'correct' on every wrong example, and 'incorrect' on every right one.
If I was right every time, I'd get 0%, and if wrong every time, I'd get 100%.
I think the site can reliably measure whether you can tell the difference, but I don't think it can reliably measure "correctness". And seems ripe for 'false positives' too.
I'm not gonna go off on a rant on this (any more than I already have ) but I think having the whole chain open to verification would be necessary before one starts down the path of evaluating their own perceptions, and perhaps 'ear training' to improve those perceptions.
I'm basically re-organizing my entire audio life at the moment, and will have the opportunity to check, and probably label, each piece of gear in the systems. Combination of testing and research. Should be fun.

Chip

 

[House de Kris]

I think you're missing the point of an ABX test. It is not about saying which is 'correct', but rather about matching the unknown to two possible knowns. Regardless of if your playback system inverts or not, you listen to the two presentations of normal and inverted to acclimate yourself to the two different presentations. When listening to the unknown, it is up to you to try and match the unknown to either of the two knowns. See? It's a matching game, has nothing to do with if your system has non-inverted or inverted absolute phase. You don't have to determine which is correct, just which version it matches.

 

[motorstereo]

Well that's something that I won't concern myself with anymore. Damned if I could a difference on my Mcintosh 2255- ADS1530's combination

 

[Chip Chester]

No worries, House... I understand A/B testing as well as ABX testing. But as you'll recall, I said I didn't take the test. Just went back to the site to make sure, and there's no mention of the test methodology on the main linked page, or the absolute phase test page (unless I've overlooked it twice now.) But obviously there is mention, even demonstration, if one actually takes the test.

In the end, we both agree the test can determine if the listener thinks the test sound matches the example sound.

Of course, a much tougher test would be to determine if absolute polarity is correct in person, with no comparison/reference sounds, one-shot, in a vacuum. Well, not actually a vacuum, because well... you know, sound waves and head explosions and all that.

Such a test would require a verified system (which would actually be easier with live sounds from an isolated room), and an in-person person sitting there. You listen to a series of sounds (blindly correct or not), make your choice after each, test over. Now that would be an interesting and highly impractical test, unless conducted en masse somewhere. Anyway, I'll just go back to putting my system back together now...

Chip

 

[OMGCat!]

After 6 tries on that ABX I got a 0% but honestly can't tell what is different about it, just that something is. I also don't know if my system is inverting or not so? I might have to look into this deeper.

 

[onplane]

After 6 tries on that ABX I got a 0% but honestly can't tell what is different about it, just that something is. I also don't know if my system is inverting or not so? I might have to look into this deeper.

OMG, it really makes no difference whether your system inverts for this test. House said it very well. The purpose of the test is NOT to test your system, but rather to test your mind. (Pattern recognition is done in your mind, not your ears.)

The test provides two know different patterns and asks whether you can identify these different patterns when presented to you randomly. Now I think I could detect a very slight difference, but the difference wasn't big enough for me to be able to distinguish between the two.

I also know that I can not hear anything beyond 10,000Hz. That might provide a partial explanation for my inability.

Regards,
Jerry

 

[JoeESP9]

Try using the sound of a trumpet. It has an extremely asymmetrical waveform.

 

[onplane]

Try using the sound of a trumpet. It has an extremely asymmetrical waveform.

I've been reading more about absolute polarity and surprisingly, a lot is on the net. Turns out recordings with string instruments might not be easy to distinguish between reversed or correct polarity. The argument in favor claims that when a string is plucked that creates an initial compression wave. Well, not so fast! Turns out a vibrating string is a very complex motion and while it's true part of the string initiates a compression wave another part of the same string is simultaneously creating an uncompressed wave.

Regards,
Jerry

 

[Audiovet]

Most musical 'sounds' are a succession of periodic waves, i.e. more than one cycle. (A single cycle cannot create a tonal sensation.) In practice, between loudspeaker and ear, a series of successive cycles of compression and rarefaction floating down to one. Reversal of absolute polarity will only exist in the first half cycle of any frequency - after that both signals are the same (unless one postulates audible non-linearity in hearing; is that what is alleged?) The physics of phase reversal elude me.

How about adding some 'd.c.' - as in doing the experiment in a positively or 'negatively' pressurised chamber. What would the expected result be?

 

[Schurkey]

Any number of CD players or D/A converters have reversed polarity at the push of a button.

Example: Adcom GCD 600/700 have a "polarity" pushbutton that digitally inverts polarity.

I couldn't hear the difference twenty-five years ago. Fairly sure I can't hear it now. Having said that, it's entirely possible that the problem is that there's no guarantee that multi-track recordings have all of the tracks in the same polarity--so reversing the polarity makes some tracks "correct" while making other tracks "incorrect", and there'll be no way to sort out that mess.

Therefore, the best chance you have of "hearing" correct polarity is with single-track recordings; probably of a single instrument or single voice; and played back through a speaker system that doesn't muck-up the phase. Ported speakers screw up phase below the resonance point, and higher-order crossovers mess up phase in the treble. The mucked-up treble phase may be "corrected" by wiring the tweeters in reverse polarity.

Nothing is as easy as it seems.

 

[orsen]

i am just learning that many parts of your system can invert the signal weather you want to call it phase or polarity
in my case it was using 2 different power amps
even tho the speakers were connected properly to both amps according to the markings on the amps and speakers
one amp never sounded right when both were on
flip the speakers leads on one amp amp voila! very noticeable difference in sound and volume
the 2 amps were at odds with each other
apparently this problem is not as likely to happen if the amps are of the same brand/ model

 

[Chip Chester]

Audiovet wrote the following:
(A sound is...) " a series of successive cycles of compression and rarefaction floating down to one."
Maybe I'm missing something. Floating down to one what? I'm pretty sure they continue their march thru the air in succession, and the first waveform remains the first waveform as long as its energy lasts. And although there are a series of + and -, one or the other will always be 'first'. Yeah, at some point the energy of the first wave will dissipate, while subsequent ones may still be audible, but that's an extreme case...

And further: "How about adding some 'd.c.' - as in doing the experiment in a positively or 'negatively' pressurised chamber. What would the expected result be?"

Tell me more about a negatively-pressurized chamber and its sound transmission characteristics. Are you talking just low barometric pressure, or are you interested in sound transmission in a vacuum... which would be quite a challenge, due to the no air molecules thing.

Even though complex musical waveforms are assymetrical, my personal un-researched belief is that it all boils down to initial waveforms. (It's quite possible others have researched it though.)

And upon reflection, this whole thread is a great testament for getting out and listening to more live, un-reinforced music.

Chip

 

[onplane]

i am just learning that many parts of your system can invert the signal weather you want to call it phase or polarity
in my case it was using 2 different power amps
even tho the speakers were connected properly to both amps according to the markings on the amps and speakers
one amp never sounded right when both were on
flip the speakers leads on one amp amp voila! very noticeable difference in sound and volume
the 2 amps were at odds with each other
apparently this problem is not as likely to happen if the amps are of the same brand/ model

Actually, in consumer equipment I believe you are only certain of amps being in phase/polarity when the amps are IDENTICAL. That is same brand, same model.

Commercial gear is a different story, because of the absolute need to cascade amplifiers.

Regards,
Jerry

 

[JoeESP9]

As a general rule of thumb the number of stages in an amplifier determines whether or not it inverts polarity. Each stage inverts polarity. So if there are an even number of stages the output does not invert. If there are an uneven number of stages the polarity will be inverted.

Conrad Johnson preamps with phono stages were known for producing inverted polarity when using the phono stage. Line level inputs did not result in inverted polarity. The equipment "Bible" that Audio magazine used to publish almost always noted whether or not an amplifier inverted polarity.

 

[for_p1]

Somewhere I read that there exists a CD designed to allow folks to test their amps for polarity inversion. Like "perfect pitch", I've read that there are people who can actually hear the difference between correct and inverted polarity audio signals. Now the reason for this that audio signals are asymmetrical. No one could hear any difference between a correct or inverted sine wave, because they are identical.

Now, I'm NOT talking about the situation where speakers are inverted to each other. I'm talking about the situation where all drivers are in phase, but somewhere in the amp, CD, tuner, pre-amp, etc. the entire signal gets inverted.

Is there a test CD that allows folks to hear the differences?

Of course, how can one be certain that their CD player doesn't do an inversion? Nevertheless, if one had such a CD, we theoretically could decide which way sounds best and adjust our systems accordingly.

Now, I happen to have an amp in my basement (collecting dust) that has a tone defeat switch. Purpose is to by-pass tone controls and provide a shorter, more direct signal path. In the process of doing that, however, signal inversion occurs (I know this because I saw it on my scope and in further checking I could see where it happens on the schematic). What I don't know, of course, is which way I'm going. That is, I never tested polarity on the entire system.

Finally, further confusing things, I don't know whether I could actually hear any difference between a correct and an inverted audio signal.

Regards,
Jerry

As was already mentioned, there is no standard in recording chain. Some commercial CDs seems to comtain inverted material. The best is to have polarity switch in preamp to choose what is best for each record (LPs have same issue too). In my system switching polarity inverts sound layers- some virtual sound sources seem to be closer or firther in virtual field, polarity swaps them beck and force. But this is likely setup specific with significant influence from speakers and room acoustic.