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In Reply to: RE: Just for the record... posted by Poles Apart on August 03, 2013 at 12:38:32
Using headphones could be open to the same criticism of second harmonic distortion.One test that would be immune to this kind of criticism would be if a bipolar speaker were used and it were constructed with complete symmetry and located symmetrically in the listening room. (I don't know if any commercial bipolar speakers meet this test, as the ones that I am familiar with have a clear "front" and "back".) With such a speaker one could reverse polarity by a 180 degree rotation of the speaker.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
Edits: 08/03/13Follow Ups:
Question, In a typical rock recording with maybe 15 to 25 microphones or more with all instruments having there own mike and overdubs done at different studios what does correct absolute phase really mean. Reversing absolute phase may make a recording sound different but I doubt it has anything to do with correct absolute polarity of the recording
Alan
The situation is complex if there is a forest of microphones, but if they are far enough apart and close enough to the individual instruments then the multiple microphones won't affect the polarity, assuming that the microphones, preamplifiers, and cabling is different. (There are two standards for pin-out on balanced XLR cabling, which can lead to confusion if different brands, e.g. different nationalities, are used.) In addition, figure 8 microphones are sometimes used and they are velocity sensitive, which means that the polarity on one side of the microphone is reversed. Some recordings have one microphone shared by two singers and if this is done with a figure 8 microphone the singers will be in opposite polarity.
Absolute polarity is most easily heard on a single microphone monaural recording played back on a single driver speaker system. Here all one needs is an AM table radio. Many multi-way speaker systems have their drivers wired in opposite polarity and they scramble phase, making it more difficult to hear the effect. As far as I know, none of the people who have done research on absolute polarity have done "live" vs. "recorded" demonstrations or showed that the correct polarity sounds better (rather than merely different as you suggested).
I have attended a jazz concert where the polarity of the PA system used on the singer was wrong. At the set break I went up to one of the band members and remarked that the polarity was wrong. He believed me, because he was getting bad sound and didn't know why. We reversed the wiring on both speakers and the second set sounded much better. There is test equipment that can be used to calibrate correct acoustic polarity. Getting acoustic polarity correct is essential in PA sound reinforcement situations.
Tony Lauck
"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar
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