[ctviggen]

I have a CD with two songs.  For each song, they have it in one polarity (the "correct" one) and then opposite polarity.  That's a total of four songs.  I listened to these songs over and over and over and over, and I couldn't tell any difference. 

[Daygloworange]

Just for fun, when I've got some time, I'll mix a master in one polarity, then flip polarity and mix another master, and burn a copy of each and see if I can hear a difference.

 I'll do it with a stereo mic set up on an acoustic guitar track, clean, simple, no B.S. We'll see.

Cheers

[Ethan Winer]

George,

> So which camp are you in? <

I didn't vote because both sides are right.

Absolute polarity can be audible, but probably only because of loudspeaker nonlinearity. That is, what you hear is not the polarity reversal itself, but rather that most loudspeakers distort differently in each cone direction. This is from my Audio Myths article:

Important Update Info: Mike Rivers from Recording magazine sent me a test Wave file that shows absolute polarity can be audible in some circumstances. The polarity.wav file (87k) is a 20 Hz sawtooth waveform that reverses polarity in the middle. Although you can indeed hear a slight increase in the low end fullness after the transition point, I'm still not 100 percent certain what this proves. I suspect what's really being shown is a nonlinearity in the playback speaker, because with a 50 Hz sawtooth waveform there is no change in timbre. However, as Mike explained to me, it really doesn't matter why the tone changes, just that it does. And I cannot disagree with that.

More Update: After discussing this further with Mike in the rec.audio.pro newsgroup I created two test files you can download and audition yourself. The Kick Drum Wave file (324 KB) contains a kick drum pattern twice, with the second reversed. Play it in SoundForge or any audio editor that has a Loop mode, so you can play it continually to see if you hear a difference. The Voice Wave file (301 KB) is the same but with me speaking, because Mike says reversing polarity on a voice is surely audible. I don't hear any difference at all. However, I have very good loudspeakers in a room with proper acoustic treatment. As explained above, if your loudspeakers can't handle low frequencies properly that could account for any difference you might hear.

[Scotty]

Does this mean that a loudspeaker drivers' measured THD or IM distortion value will vary if the test signal is reversed in polarity. Could you present the test measurement methodology you used that lead you to this conclusion.
I can see this phenomenon explaining what I heard when playing back Sheffield Lab recordings through Magnaplaner loudspeakers.These recordings  have instructions included which recommended  reversing phase upon playback
for the best results. Maggies have asymetric drive as a consequence of their magnets being on only one side of their diaphragm which results in rapidly increasing second harmonic distortion with increased drive levels.
Scotty

[Doublej]

Daygloworange

I agree with your assessment of my description but what I failed to mention is that the setup was outdoors on a deck with the speakers about 15 feet apart so there wasn't any interaction between the two. Discounting the difference in content between the left and right channels it was listening to one speaker with polarity X and the other with polarity Y. When we moved from being in front of one speaker to the other it was clearly discernible difference. We both honed in on the left speaker as sounding wrong. This was the one with the leads reversed.

This topic, like most regarding absolute polarity, has somehow reverted to talking about speakers being out of phase with one another.  That is a completely diferrent topic, and does not require debate.  Out of phase speakers (where a mono signal sounds ethereal with no real center image) is a problem with one speaker having it's leads reversed.  It is not a debate about absolute polarity in recordings, polarity switches or the like.  Two different animals all together.

OH BOY....
It hasn't reverted to talking about speakers out of phase with each other unless two $50 bookshelf speakers, 15 feet apart, sitting atop a wood fence have any significant interaction between each other when one put their head two feet in front of each speaker. I certainly didn't hear the music "in stereo" that day with the speakers in or out of phase with each other.

[ted_b]

Daygloworange

I agree with your assessment of my description but what I failed to mention is that the setup was outdoors on a deck with the speakers about 15 feet apart so there wasn't any interaction between the two. Discounting the difference in content between the left and right channels it was listening to one speaker with polarity X and the other with polarity Y. When we moved from being in front of one speaker to the other it was clearly discernible difference. We both honed in on the left speaker as sounding wrong. This was the one with the leads reversed.

This topic, like most regarding absolute polarity, has somehow reverted to talking about speakers being out of phase with one another.  That is a completely diferrent topic, and does not require debate.  Out of phase speakers (where a mono signal sounds ethereal with no real center image) is a problem with one speaker having it's leads reversed.  It is not a debate about absolute polarity in recordings, polarity switches or the like.  Two different animals all together.

OH BOY....
It hasn't reverted to talking about speakers out of phase with each other unless two $50 bookshelf speakers, 15 feet apart, sitting atop a wood fence have any significant interaction between each other when one put their head two feet in front of each speaker. I certainly didn't hear the music "in stereo" that day with the speakers in or out of phase with each other.

Doublej,
Oops sorry, my bad.  You're right, if they are so far apart and you don't listen to the stereo image, you're likely not experiencing out of phase phenomena.  I jumped the gun, cuz most absolute polarity discussions end up being mixed in with out of phase discussions. 

[Ethan Winer]

Scotty,

> Does this mean that a loudspeaker drivers' measured THD or IM distortion value will vary if the test signal is reversed in polarity. <

It depends on the symmetry of the test signal. With a sine wave the same thing happens either way so there will be no change. With a sawtooth wave as in the example files I posted that you can download, then a difference is possible.

This type of distortion is caused by the sub's excursion not exactly matching the driving source signal. For example, at loud volumes the cone needs a large excursion. At some point it simply can't go any farther because the cone is being stretched too tightly, so the tops of the resulting sound waves are flattened. If the speaker responds differently pushing out versus pulling in, then the distortion and/or output level will change with polarity with a non-symmetrical signal.

> Could you present the test measurement methodology you used that lead you to this conclusion. <

I did this by listening and using logic.

As explained in my other post above, at 20 Hz, which is below the 25 Hz resonance of my big JBL speakers, the sound did change where the wave reverses. But at 50 Hz the sound was the same. So I concluded the reason the sound changed is due to loudspeaker nonlinearity at 20 Hz. As opposed to absolute polarity being audible.

It may well be that in some situations, with some types of source material, and with some speakers, that absolute polarity per se can be reliably detected. But in the grand scheme of things this is way down the list of what matters. It's certainly far less important than, say, having adequate bass trapping.

--Ethan