Here's the quote from the article on sterophile.com.

My questions are:

Does CD polarity exist?

If so how can check the polarity of my CDs?

Does the direction of the polarity make a quality difference as suggested by this article?

Or is this Cyrus guy ?

It should be about the drive he uses. EAC has a "Swap channels" option as well for this purpose. The originals are ripped swapped.

atici,

Thanks, that makes sense, I'm familiar with the "swap channesl" on EAC. I didn't understand what he meant by "polarity."

Umm, polarity usually refers to positive/negative, not left/right. The guy seems to be claiming that basically, his CD copier multiplies all sample values by -1. I seriously doubt he could hear the difference, since humans are generally insensitive to such phase shifts. I wouldn't worry about such "polarity problems" at all - the only case where such a thing might cause problems is when a sample at -32768 is inverted, since there's no positive 32768.

Don't think so. That's called inverting. If you invert a wave vertically the sound you'll hear will be completely nonsense.

I think the polarity isn't related to left-right channels, but to whether the wave (in a single channel) goes up or down.

To reverse polatiry, you'd multiply the wave by -1. If you do this to just one channel, the recording will sound odd, especially with headphones. If you invert both channels, I'd wager the difference is inaudible.

Edit: Chun-Yu got here first!

P.S. Why am I not surprised that a "stereophile" would find the most time-consuming, cost-inefficient method of dealing with an audio (non-)issue? Inverting the wave with an audio editor beforehand would be faster than burning, plus it wouldn't use an extra CD, and it wouldn't create another opportunity for errors to be added to the audio.

Edit 2: Hah, read the bottom of the page. It's another Auric Illuminator user!

Not at all. Take a sinewave, and multiply it by -1 (reverse the polarity, invert it, flip it, what have you). It will sound just like it did before.

But sine wave is symmetric (Well, almost it will correspond to a time shift which won't be audible) And why do you flip it again?

I remember in the good ole' days with my Amiga and Audiomaster when I inverted any sample it sounded completely nonsense. And so did it with the horizontal (time domain) flip But maybe it was something else though I am almost sure.

BTW I agree with you that using another CD is such a bad idea.

Thanks everyone for replying, but how can one determine the polarity of a CD and compare it against the original?

BTW, from the physics that I remember from college, Chun-Yu's and SometimesWarrior's theory makes more sense.

My physics was quite good but doesn't make any sense to me. I don't think inverting any kind of wave would sound indistinguishable except for waves like sine... What am I missing?

Offtopic: Maybe in the dual universe (where anti-atoms are made of positrons and negatrons) anti-me is listening to the inverted version of the song I am listening to now...

atici,

I'm thinking of the phase example. If you reverse the polarity (switch the positive for the negative) on both your speakers, it will sound exactly the same. However if you only switch one, you'll notice some sound cancelling, especially in the low fequency range, and more so if the track is monaural. The latter is "out of phase," but the former is "in phase" but the polarity is reversed.

Who knows, that Cyrus guy could have meant something completely different by "polarity," we won't know for sure.

That's right ! The speaker polarity example explains what should be going on. However I remember inverting waves and remember they sounded silly.

well you're remembering something else. Try it now and see for yourself, doesn't sound any different, as it shouldn't.

atici,

Inverting and shifting the phase of wave are two different functions. Phase shift is exactly what it sounds like; how far to the left or right a wave shifts. An inversion is flipping the wave, so that what is on top is now on the bottom, and vice versa. So you are correct in that inversion sounds different.

PS-Of course if the wave is entirely symmetrical (a sine or cosine) then flipping it wont matter, but if it isn't, such as the waves produced by music and the natural world, you'll notice a difference upon inversion.

Installed and tried with Cool Edit. Yeah guys sorry you were right all along it sounds same. Cool

Now it's 4.18 am, bedtime...

i was almost under the impression that the question was asking if the cd was stable at a molecular level until i read the little quote box, there is an area called "superparamagnetism" which can calculate/predict how long a bit will last before it (randomly) changes polarity giving you an error of some form. but thats irrelevant in this case isn't it.

To check the porlarity of your CDs, extract the original and the copy, and use EAC to perform a "compare wavs".

I'm so much on the Internet, that I can't remember now where I read about the audibility of polarity inversion. It was a scientific paper with listening tests. It said that on some instruments (the was a piano, AFAIR), the listeners could not tell the difference, but that it was audible on some artificially generated signals for this purpose, and that, AFAIR, it may be audible on percussive instruments.
There was also a discussion about amplifiers possibly inverting polarity, and the consequences it would have in mixing, when making a multitrack recording of an orchestra with several microphones. Wasn't it linked here ? Can someone remember about it ?