Pro Audio Asylum

Posted by Tony Lauck (A) on December 21, 2008 at 11:59:32

In Reply to: RE: More about Absolute Polarity posted by harecording on December 17, 2008 at 04:10:51

If you have sine waves they will sound the same in either polarity, as the waveform of an undistorted sine wave is completely symmetrical. If you want to try detecting polarity with constant tones, you can mix in 2nd harmonic distortion at various phases. This can be done easily using audio editing software which has waveform generating features. You can create a mixture of fundamental and second overtone at any amplitude and phase you wish. Detection results will be best if tones are well below 1 kHz as that is pushing the range at which the auditory nerve fires synchronously with the acoustic waveform. Above a cutoff only amplitude information makes it to the brain, according to the research that I have read. I have had better results detecting absolute polarity when listening to music rather than test tones.

It is equally convenient for me to adjust playback polarity as volume. I use both controls about the same amount when adjusting playback so that a given recording sounds at its best. However, most of the recordings that I listen to are minimally miked Classical and Jazz recordings, which tend to show up polarity much more than multiple miked complex mixes.

After trying both polarities with many different Classical and Jazz recordings, if you still don't hear differences it may be that your speakers aren't phase coherent enough. Try playing back through a single driver speaker setup. It need not be fancy. A cheap table radio should do just fine.

I have found it best not to listen to the tone of the instruments, just the general ambiance. If you can achieve a Zen mind it will be easier to detect polarity differences. Over time you will gain experience and be better able to hear polarity right away and predict whether the sound is likely to improve if you reverse the polarity. However, at least in my case, this ability varies from day to day.

Enjoy. It is a fun game to play and a cheap tweak.

Tony Lauck

"Diversity is the law of nature; no two entities in this universe are uniform." - P.R. Sarkar