@akg_ca
Thank you. To be clear, I was happy with the TonTragers, and do believe that they are well-designed to compliment Harbeth speakers. My pedantry stems primarily from my experiences with isolation devices under speakers, which, when properly designed, do decouple the speakers from the floor. And yes, in my view, and more than a few others, the difference is meaningful.
Interestingly, I engaged in a related experiment with my 30.1/TonTrager combo before I moved on to my current system. I was able to purchase a discounted pair of Townsend Podiums, and tried them. The Podiums are considered by some to be the best of the various speaker isolation options, albeit at a steep price.
Well, my experience was not good, but I do not blame the Townsend product at all. In my view, it was the lack of hard coupling between the 30.1 and TonTragers that caused the failed experiment. Also, consider that there can be a perceived lack of bass impact with such decoupling, and given that the bass of the 30.1 is limited to begin with, that was in issue.
For further perspective, I tried – and kept – Isoacoustic Gaias under my FinkTeam KIM speakers, and consider the improvement to be substantial. The Gaias are probably the most widely used speaker isolation devices, and some high-end companies now supply them as standard equipment.
Note that I am not arguing that the Gaias are in some way superior to the Townsend Podiums (except in terms of value). But my KIMs, which are also stand-mounted, are hard-coupled, and as the stands are metal, the Gais can be screwed directly into them, providing further, crucial hard-coupling.
Finally, as you pointed out above, the BBC type speakers are designed to resonate, so even if hard-coupling could be achieved, I am not certain to what extent they would benefit from feet that are designed to both isolate and provide vibration control.