Non inverting polarity?

Honest1...Your test method is clever, and your results interesting, although I would have to try it myself to be convinced.

"Jeffreybehr...I just found out that all JBL loudspeaker drivers have polarity opposite to other brands. A positive voltage applied to the + terminal causes the cone to pull in (not push out). So, if you think absolute polarity matters, and you have JBL speakers, hook them up backwards."

Hmm...I didn't know that.

An easy way to test your speakers is with a 9-volt battery. After disconnecting the positive speakercable lead, use jumpers from the battery to the speaker terminals to see which way the cone moves initially. If the cone moves out--ie toward the listener--when the positive (small) battery terminal is connected to the red terminal, the speaker is wired correctly. This test works well for bass and midrange drivers but is really tough to see on a tweeter because only the initial spike of the DC voltage passes the crossover. Maybe using a magnifying glass would help one see it move.
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You are correct that some manufacturers use 2 for non-inverted and some use 3.

All sound starts out being single ended in the sense that there are compressions and rarefactions in the air that can be coverted to a corresponding electrical signal with positive and negative amplitudes. There is no such thing as balanced sound waves, only balanced electrical signals.

Some time ago somebody figured out that most of the elctrical noise getting on their wires between components could be canceled if they first took the original signal (the non-inverted) and inverted it, then pass these two signals separately down the amplification chain, amplifying the difference in them as they go. The noise that was picked up by the wires will not be amplified because the system only amplifies the difference in the two lines, and the noise is the same on both lines. Very clever.

This was very handy in noisy enviroments with lots of equipment like recording studios and with wires over long distances. The drawback is that the circuitry is more complex from beginning to end since you essentially have two amplification chains for each channel, four total for stereo, that have to be perfectly balanced to get the full benefit of the noise cancellation, and it will introduce distortions if it is not.

Then a really clever fellow saw that he could make balanced equipment for the home market, market it as better because "that's what the pros use" and cash in on a gullible public even though almost nobody in a home enviroment suffers from the type of noise problems that these circuits are good for. The cable fellows were delighted because they could charge a lot more for balanced cables even though the increased cost in materials was negligible.

Stick with single ended. It's cheaper, works just as well or better in your home, and you don't have to worry about which pin is hot on your cables.

Eldart - I agree - I didn't believe it until I tried it, and then kept trying it, and the perfect results forced me to believe. I don't know why it should matter - either way the cone is moving back and forth, many times to make even the quickest note. I can't imagine how I could tell which direction it started. I didn't want to believe it, for fear that I would become paranoid about which way each recording shopuld be played (as had the person who convinced me to try it. He was so into it, he said he could not listen to one recording because the vocals were recorded in correct polarity and the piano in opposite polarity! I felt so bad for him!)