Suspensions on turntable...really effective?

Of course the spring can be an air spring, air being a compressible fluid, no? And designed just like steel compression springs to have a certain spring rate, which one selects for the load under consideration. Did I forget to mention my sub Hertz iso stand of yore was an air spring design? Of course, like everything else air spring designs are complicated by internal friction and damping. Some air springs have too much friction and or internal damping. And my single spring "Unipivot" Nimbus platform achieved 0.5 Hz resonance frequency in several directions. The Nimbus was also the only iso stand with six - count ’em! - directions of isolation.

The claim that Basis makes is that the suspension works both to isolate the plinth from structure-born vibration (i.e., from the outside and from the turntable motor) and to dissipate vibration created by the interaction of the stylus tracing the groove (primarily energy transmitted from the arm into the plinth).  The supposed downside is that decoupling the plinth from the motor introduces one additional element that may cause instability in the speed of the platter (Michael Fremer, the reviewer from Stereophile speculated, but never demonstrated, that the plinth could rock back and forth and this would change the platter speed).

 What I do know about my Basis Debut table (with the vacuum clamp) is that it does an amazing job of isolating the arm/cartridge from external vibration and at dissipating energy generated at the interface of the record and stylus.  If you place the stylus on a static record and hit the support surface that the turntable is on, very little gets played through the system (as heard at the speaker).  Also, if you tap the surface of the record itself close to the cartridge, the Basis tables also transmit far less energy to the cartridge than most table/arm combinations.  This translates into much less obtrusively loud ticks and pops; the energy of such sharp impulses is damped very quickly and effectively.  However, it is a matter of taste and system tuning as to whether such high damping of vibrational energy is desirable or not.

The Verdier tables are also in the highly damped camp.  The sound is "dark," and like the Basis tables, some might call it "dead" sounding.  I like the Verdier tables a lot.  Whether it is magnetic suspension, the extreme mass, the isolation of the motor by placing it on a completely different platform, or any number on other design factors, these tables sound good to me.

In fluid mechanics we consider air a compressible fluid. This is not to say it's a liquid.

Sorry for the newbie question, but just wanna make sure I get it right...resonant frequency is the frequency that passes thru the whole suspension and gets transferred to or received/absorbed by the plinth, platter or whatever is above the suspension?

So, frequencies other than that resonant frequency gets isolated/inhibited/blocked?

Or only frequencies above the resonant frequency gets blocked?