Originally Posted by G. E.
... its a high mass stand with internal damping ...
Talking 'bout mechanics: I've never calculated the actual forced oscillation of the stand but I've noticed that knocking pretty hard against the stand/speaker-unit it "swings" 2-3 times within a second before it stops. Amplitude on top of the speaker may be +-1mm [~0.04"]. So the Eigenmode (in the bass-cabinet axis) of the mechanical system seems to be around a few Hz and is therefore subtancially lower and pretty much decoupled from the audible frequency-range
of the speaker.