Tonearm mount on the plinth or on Pillar ?

Dear Halcro, You wrote, "The fact that you and many others can listen to vinyl played back at excessive volumes demonstrates conclusively that air-borne sound waves have no effects on the turntable system."  But that is an incorrect assumption based on all my past experience.  I have been present many times, in many different listening venues, when acoustic feedback causing distortion was sound-pressure-dependent.  Backing off the volume control could reduce the effect and eventually eliminate it entirely, in these instances. Perhaps this is not a problem in your house, but it is a real phenomenon in some others. In the case that Atma-sphere (Ralph) describes, perhaps conditions were such that there was no appreciable acoustic feedback, even at 100+ db. It's possible.  Careful set-up and room damping can indeed eliminate or remove the problem, but that does not mean it does not exist.

Dentdog, More to the point, is your Terminator tonearm mounted on your Salvation turntable or is it on an outboard arm pod, separate from the turntable?  The Resomat is indeed a contrarian design in that it specifically decouples the LP from the platter, whereas most platter mats make an attempt at coupling to facilitate the dissipation of spurious energy delivered into the vinyl by the passage of the stylus in the groove.  Many do say the Resomat works great, however.  Which should make us re-examine the theory of the platter mat.

Lewm, the Terminator tonearm actually pivots vertically on two contact points of an underslung carriage. This is joined to a sliding metal inverted V bearing which slides horizontally on a similar inverted arm,separated by a thin cushion of air. A pump with very low pressure allows for a long thin surface, decoupled by air. Thus the arm can pivot vertically while the sliding inverted bearing moves without resistance, [air cushion]. The support arm under the inverted bearing is attached to the plinth, with the air cushion separating the bearing from the support arm. The air cushion completely separates the inverted bearing and the undercarriage from the support arm and the plinth.
As to the resomat, I have experimented with three other mats and in each case the dynamics I was accustomed to hearing were sucked out of the music.This was without doubt the most dramatic negative change I have heard in the system. The music just died. Needless to say the resomat is in place permanently.
While I have formally studied physics on a basic level and have some limited understanding of airborne/foundational vibrations, in no way am I qualified to refute or support either of the theories being bandied about here. I do know however that the above methods put into effect, including the magnetic bearing supporting the platter all work to decouple all the working parts. This to me seems to reduce the chances of resonant/non-resonant vibrations being transported throughout the playback system. Totally contrarian I realize, but it works and to me it works better than what I have heard otherwise, particularly in the case of high db playback.
My ego isn't really attached to this, so anyone who wishes to shoot it down, have at it.

Dentdog, There is no need to be apologetic regarding your affection for the Resomat.  You have lots of respectable company in that regard.  Like I may have written elsewhere, if not here, I am curious to try one myself.  In the past year, I had an epiphany in the opposite direction.  Since the mat (of any kind) sits in contact with the platter, more or less in the case of the Resomat, I don't think this directly pertains to the arm pod discussion. I was long an enemy of record weights and the like devices, believing that they "killed" the dynamic extremes of music, in parallel with your experience using other platter mats. Then I acquired an original record weight and peripheral ring made by Kenwood for the L07D, just to have them, since I own an L07D. By chance I have found that the L07D record weight used in conjunction with a Boston Audio Mat1 or Mat2 or the stainless steel mat on the L07D sounds much better, even more "lively", than the mats without the record weight.  I don't believe for a minute that there is any magic in the L07D record weight, by the way; the experience merely suggests that my earlier suppositions were incorrect. Probably any good weight of similar mass would work as well. It's a weird hobby.  

By the way, I also think that maglev of the platter mostly acts to relieve pressure on the bearing and possibly contribute to a lower rumble figure, but I don't think it does much to isolate the platter, at least not in a major way.  So, your findings there do not add or subtract from the debate about arm pods.  

I do take your point about the Terminator tonearm; because they are riding on a cushion of air that would seem to isolate the arm itself from the underlying structure, the Terminator and other air bearing tonearms could be said to mimic the effect of an outboard arm pod, albeit I do believe from what you wrote that the understructure of the Terminator is directly bolted to the plinth. In which case the coupling or lack thereof would be a function of the air pressure and other aspects of the interface between the moving arm wand and its carriage.

Throughout this thread arguments on both sides seem to have merit. I will say Ralph's data is the most convincing given that he has measurements to support his viewpoint. It would be interesting to see some data involving the turntable  setup where the turntable functions from a different room isolated from the airborne and to some extent transmission through the structure of the playback room. 
During my college years I often listened to a system in which that was the case. In this case it was absolutely necessary or the stylus would fly off the table otherwise. We listened kinda loud! I still do.
I really enjoy these kinds of discussions, always a lot to learn here. A similar discussion about spiking vs isolation of speakers on WBF is equally intriguing. Even the propagator of Stillpoints began to question his product and we all know what a wonderful system that is.

Does this plinth-tonearm arrangement represent "closed loop" solution ?