theaudiotweak,
Roger
Many years ago Polk Audio used laser interferometry [probably from Johns Hopkins] to measure the cabinet motion of a new time aligned speaker. They found a speaker that sits directly on a hard surface or a carpet over foam floor and played at a reasonable volume level causes the cabinet to travel further than the excursion of the tweeter. This cabinet activity greatly reduces the advantages of time alignment. Would this severe cabinet motion with drivers enclosed or attached also create unwanted and audible Doppler distortion? TomYes I would say it has to have an impact although the underlying time alignment is still valid and the additional vibrations (caused by the cabinet) will add blur to an "aligned" image. IOW objects would have an average (out of focus) location contaminated at least in part by the motion of the cabinet.
Roger