As others already pointed out, the physically visible woofer pumping is typically seen when the woofer is mounted in a ported or vented cabinet that does not backload the woofer at extreme low frequencies. You’d never see it with acoustic suspension type speakers for example. ( I don’t know about Zu speaker designs or how your Tannoys are enclosed.)
incidentally we’re seated in the Kennedy Center, and my first live post covid concert is about to commence.
incidentally we’re seated in the Kennedy Center, and my first live post covid concert is about to commence.