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Polarity makes a bigger difference for amplifiers and speakers with asymmetric transfer functions - i.e., those with high even-order harmonic distortion. When your "hifi" system amplifies the positive and negative halves of the signal differently, the effects of reversing phase will be greater - and not due entirely to the music, but to the reproduction
Polarity makes a bigger difference for amplifiers and speakers with asymmetric transfer functions - i.e., those with high even-order harmonic distortion. When your "hifi" system amplifies the positive and negative halves of the signal differently, the effects of reversing phase will be greater - and not due entirely to the music, but to the reproduction Thumbs up
Well said Andy. As one who is sensitive to correct polarity, it makes a big difference for me. Couldn't live without that switch. Mine is in the digital domain. no invert switch on preamp. The phono stage has one as well. I have found that LPs are the worst culprits. Some with the bass out of phase some just all out of phase. Love that switch.
Yes, could you make it even clearer for EEs to understand.
Amplifiers that produce even order (like, 2nd order, 4th order...) harmonic distortion do so because they amplify asymmetrically - with a curved transfer function that leads to waveforms with differing distortions to the tops and bottoms. Amplifiers that produce odd order (like, 3rd order, 5th order...) harmonic distortion exhibit symmetric distortion - with a curved transfer function that leads to the same form of distortion on the peaks and troughs of the signal waveform. The audio perception of the asymmetrically-distorted signal varies more dramatically with polarity, since the waveform now looks quite different if you turn it upside down.An example of this would be single-ended triode amplifiers, which tend to produce even harmonic distortion, due to inherent asymmetry. Push-pull amplifiers (tube and solid state) are able to cancel this asymmetric distortion, and thus tend to contribute symmetric distortion (3rd harmonic) - although in much lower levels. When people claim that they can hear absolute polarity more easily with a SET amplifier than solid state or push-pull tube, it is because the amplifier enhances to the asymmetry of the signal (especially at higher output levels), leading to greater discernibility of signal phase. Of course there are many variables... all amplifiers exhibit distortion, and usually both odd and even order components are present. And, some amps do distort more than others.
Thanks, Jon - great explanation. So if "Push-pull amplifiers (tube and solid state) are able to cancel this asymmetric distortion, and thus tend to contribute symmetric distortion (3rd harmonic) - although in much lower levels", does that mean that push-pull tube amps produce 3rd harmonic distrortion just like ss amps do? In fact they may well produce higher levels?And what about 5th / 7th HD etc?Thanks,Andy
Quote from: clarkjohnsen on 19 Oct 2008, 06:28 pm"Music normally creates compression waves. Electronics, however, often invert that natural, positive polarity to unnatural, negative rarefaction, thus diminishing physical and aesthetic impact. The term Absolute Polarity uniquely describes the correct arrival to the ear of wavefronts from loudspeakers, with respect to actual musical instruments.That part is wrong. It's just not true that "music creates compression waves".
"Music normally creates compression waves. Electronics, however, often invert that natural, positive polarity to unnatural, negative rarefaction, thus diminishing physical and aesthetic impact. The term Absolute Polarity uniquely describes the correct arrival to the ear of wavefronts from loudspeakers, with respect to actual musical instruments.
First off, all sound waves consist of an alternating series of rarefactions (lower air pressure) and compressions (higher air pressure) - that's what a sound wave IS. When the wavefront arrives at your ears/mic, the first deviation from average pressure can be either of the two. Now probably what you mean is that the leading edge of the wave generated by a musical instrument is a compression. But that's not correct either - vibrating objects can either create compression OR rarefaction wavefronts, depending on how you strike or pluck them and where you're standing.
I've done the experiment myself to verify that - I took a string, plucked it, and recorded the result with a mic. As expected, whether the leading edge of the waveform was compression or rarefaction depended on which direction I pulled the string before releasing it. Same goes for percussion - you can flick a pen with your fingernail, strike a gong, hit a cymbal - the leading edge will be either rarefaction or compression depending on where you are standing relative to the direction the pen/gong/cymbal was struck from. For something more complex like a violin, I suspect the leading edge will still depend to some extent on the direction of the bow stroke and the position of the listener, but I haven't tried to verify that.
If you don't believe me, with a cheap mic and a laptop you verify it yourself in five minutes. Just record the sound of flicking a pen (or paper or probably anything else). Do it once flicking towards the mic, and once away, and see for yourself.
But if you then flicked a phase reversal switch on the tape/CD-R machine, so that the recording was now playing back at you with reverse absolute polarity, it would sound different - strange in fact. This is because you are no longer hearing the true leading edge of the notes.
Actually the difference is quite subtle. I happen to have an audiophile test CD (from Chesky Records) in which there's a recording of trumpet note and then the polarity-reversed version. I haven't tried to ABX it, but the difference is really small even over phase-coherent headphones.
If you say you can't hear absolute phase change then IMO there are two possibilities:1. you have speakers which use higher-order crossovers which require one driver to be connected in reverse ... this makes it very difficult to pick up absolute polarity issues. (Mine are like that. )2. you are one of those people who are not particularly sensitive to it (which is perhaps a blessing! ).
There is a third possibility which IMHO is far more probable. Many audio systems induce significant distortion. If the distortion is asymmetric with respect to zero voltage - which is usually the case - reversing the polarity will make an audible difference on any recording which is itself asymmetric (and that's almost everything other than pure single test tones). So my hypothesis is that people that hear clear differences are listening through systems that induce lots of harmonic distortion, hence making the effect clearly audible. If instead you listen through a low-distortion system, the effect is extremely subtle (generally it's audible only under artificial circumstances).
Vinyl setups are notorious for high levels of asymmetric distortion.
It's just like recording live with an audience. after the bands done playing and your hear the audience, it sounds different Sure, it sounds different, because the polar response of the microphone is usually piss-poor from the rear and you were actually recording secondary reflected sound waves that entered the front or sides of the microphone, because the cardioid microphone still picks up the best from the front and gets worse the farther off axis you go.
If we then take that analogy to air, no mater what sound we make it will be in a positive manner, wheather I click the pen facing forwards or backwards, shake the sheet of paper forwards or backwards. it all created positive pressure.Movement always causes a positive air displacement. (pressure).Wayner
We all know that microphones are hit from all sides from direct and reflected sound simultaneously. The diaphragm can't move in both directions (at one time) so one is going to win. That winner is the strongest wave.
