“Black background” — What really contributes to this phenomenon?

Miller's whining on about springs again.   Boing boing.
Just the wrong way to go.  Equipment shouldn't be allowed to oscillate.
Particularly speakers, springs lead to fuzzy unfocussed sound. Blowing in the wind.
Even TT designers have mostly moved from spring suspension to mass loading in the last 10-15 years.
And the more mass the better.