DCAudioDIY.com

I thought this was pretty good
Skip the first 6 mins.
I am going to change the way I measure systems because of this
https://youtu.be/VHjdh-Vka-g

Interesting but not convincing. In the stereo, polarity difference effects the sound staging, not the tone or timber.

I didn't watch the video but comb filtering refers to interference patterns caused by any sound sources, whether generators or reflectors that cause enhancements and cancellations to a propagated sound due to distances between them. The term "comb" refers to the amplitude response changes as the receptor moves to different positions between the sources. Those amplitude variations repeat in a fashion so that the amplitude response plot looks like the fingers of a hair comb. As you move along the "fingers" of the comb, the intensities change.

Here is what it looks like: