My understanding is that nothing beats active when it comes to keeping floor borne vibrations from reaching equipment. Passives like CMS, HRS, SRA and Symposium serve as grounds for equipment vibration (self, like motors and transformers and airborne) and convert that to low grade heat. The passives attenuate floor borne vibrations by making the path directional using interfaces (spikes, elbows) but do not cancel. If my understanding is correct then some context may be required in the decision making process. If I were say in an area with heavy traffic, perhaps a railway even or have suspended floors, in other words heavy subsonic activity, actives become more desirable. Absent that the passives deal with self noise so benefits can be had even without high airborne vibrations via loudspeaker output and can be heard at normal listening levels. I like the four brands above because their surfaces have no play and are quite rigid. They won't be playing pass the hot potato with a piece of equipment with lightly sprung suspensions like say my Townshend Rock 7. Theoretically then my assumption is that the holy grail would be a passive platform designed to work on an active base. The caveat is that some people actually like their sympathetic resonances. As far as I'm concerned, that is fine too.
Oh I guess I should also share that I find that some gear are less critical of platforms because of how they are built. Equipment using stamped plates instead of crazy "overkill" construction IME always result in a bigger difference even if both have their internal components suspended or damped.
Oh I guess I should also share that I find that some gear are less critical of platforms because of how they are built. Equipment using stamped plates instead of crazy "overkill" construction IME always result in a bigger difference even if both have their internal components suspended or damped.