Absolute phase, or more properly 'polarity', has long been a hot topic. The concept is simple. In a stereo system a positive going waveform should result in the speaker driver moving forward, pushing and compressing the air in the room, rather than pulling and decompressing it, on the leading edge of the instrument or vocal 'attack'. This is all good until the actual recording itself was made in the wrong polarity. Many of us hear great differences when reversing the polarity of the recording. My friend, George Louis refers to himself as the Polarity Pundit, so dedicated to making people aware of this problem as he is. I have often questioned why this occurs. It clearly does, I can hear major changes on a per-recording basis. Others can't. One of my favorite authors, Soundminded (aka Mark Fisher) has weighed in with perhaps the best explanation I've yet read. "When studying how these instruments vibrate, they vibrate in complex modes called Bessel functions. One part of a string or drum head is moving in one direction while another part is moving in the opposite direction. If you could see the vibrations they’d look like the surface of the sea, seemingly incoherent. But they are not. This is the string or drum head or triangle breaking up into its fundamental and harmonics. You could look at it as vibrating at each of those frequencies one at a time and then adding them together. When they vibrate at harmonic frequencies the string or drum head break up, different parts moving in opposite directions at any given moment. In these cases the term absolute phase makes no sense because whether the first vibration reaching your ear is a compression or rarefaction depends on where you are listening from. Walk around a violinist while he’s playing and see if you hear any difference. For blown through instruments, horns which are brass and woodwind instruments, pipe organs, and the human voice the first arriving sound wave is always a compression. This is because air is always blown out through them, never sucked into them. In controlled tests some people are sensitive to phase reversal and some are not." Thanks Mark!
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