Invert ?

@yogiboy  i watched the video. TY.  But  As Denzel Washington said in the movie Philadelphia “ Explain this to me like I’m a 2 yr old because there’s an element to this thing I can’t get through my thick head. 🤦‍♂️🤷‍♂️

When an instrument first emits a sound, the wave starts as a positive pressure that rises and falls followed by a negative pressure (lower than the initial static pressure before the sound wave arrived).  Ideally, the speaker should follow the same pattern as the original sound wave.  But, in the many steps of the recording and playback process, the correct order of compress first (or vice versa) followed by negative pressure may be reversed.  Since, almost all recordings involve multiple microphones and line feeds, any one such feed could be inverted, so the effects of inverting polarity in your linestage may be very subtle and one position may not clearly be superior to another even when differences can be heard.

Because your gear itself can be inverting phase, you may not know whether or not your system is generally inverting phase.  The effect of such inversion is subtle enough that it is not easy to make a reliable comparison by switching around the speaker connection, and a more instantaneous comparison via an inversion switch is helpful.

Why don’t most better gear offer this switch?  This capability involves adding another active stage that theoretically degrades the signal. 

@larryi Nice explanation.  Thanks!

@mwh777  +1. Great explanation

Pual Mc educated me decades ago, except he incorrectly calls Polarity Phase, which he admitted. I  first learned about it when I had Genesis Vs with powered sub, which had RC of volume and Polarity. I discovered the biggest offender was bass Polarity. If you're looking for a sub IMO, best is one with RC of Polarity. That said Polarity/phase on a remote preamp or integrated is very meaningful to my ears

hth

Play some music you know that has good bass (make sure your speaker cables are connected correctly). Flip the switch and listen for any change to the bass. whichever position has the most bass is the correct polarity.