The reason for “isolating speakers” is not really to prevent vibrations from the floor being transmitted to the speakers, although that would occur, it’s to prevent the vibrations from speaker cabinets being transmitted to the front end electronics via the floor (mechanical feedback). Isolation systems are two-way 🔚🔜 systems, as illustrated in that Townshend YouTube video - they attenuate vibrations in both directions!
I suggest isolating subwoofers for two reasons - (1) they are easier to isolate and (2) their frequencies are lower than speakers and do more damage potentially. In a perfect world everything would be isolated - cables, power supplies, DAC, solid state amplifier. The reason speakers with high center of gravity are a problem is that springs under load lack sufficient later support unless the springs are placed far apart from each other in a wide pattern. That wide pattern of springs is much more stable. Small springs are more stable than taller springs.
I suggest isolating subwoofers for two reasons - (1) they are easier to isolate and (2) their frequencies are lower than speakers and do more damage potentially. In a perfect world everything would be isolated - cables, power supplies, DAC, solid state amplifier. The reason speakers with high center of gravity are a problem is that springs under load lack sufficient later support unless the springs are placed far apart from each other in a wide pattern. That wide pattern of springs is much more stable. Small springs are more stable than taller springs.