Why does pulling out main speakers from wall improve sound?

Good video @yyzsantabarbara , it's my post from above but in easier to understand video form. They don't address how boundary reinforcement though and how to deal with it.

Some Great Explanations Here…

or your Dealer is either “pulling-your-leg”

…perhaps didn’t understand your question…

failed at a bad joke…or is on “the” CracK. 

 I assume that because bass spreads out in all directions - 360 degrees. Being too close to walls increases the bass as well as muddying the sound. 

From Physics I seem to remember that sound waves reverse phase every time they bounce off a hard surface. I've put on a signal generator for various frequencies and tracked results using a handheld sound pressure level meter to measure changes in volume as I've moved the speaker. My best guess is that the sound waves reenforce at some spots and frequencies and (try to) cancel at other frequencies at the same spot. how significant is this? Not very. All said and done, the direct radiation path is more significant than all other indirect paths in my small room. I don't argue; I just listen.

While responding to another post, I was reminded of the Dutch and Dutch 8C. They address the issue in a different way:

1) They use mainly acoustic methods to present an out-of-phase "midrange" signal at the sides, to cancel the midrange as it is "wrapping" around the cabinet. Quotes around midrange as it will be frequency controlled.  This would replace acoustic treatment with a traditional speaker.

2) They accept boundary reinforcement in bass frequencies and provide DSP correction, something that can be done with any speaker.