Geoffkait: Your experience and your way of dealing with the results, really gave me a "belly laugh". Thanks for that!
I don't want to in any way disregard Richardkrebs personal results. I believe it would be half-hazard and wrong to do so. I respect his thoughts and his journey. I find all of this fascinating and don't want to, in any way, discourage others from posting on their results.
My feeling regarding different materials used, is that each individual material has a resonant frequency response (in terms of audio reproduction) that is really what the end user hears. How these different materials are applied is the ultimate question.
My current motor enclosure has extensive use of lead shot in two ways. The bottom surface is encased with small gauge lead shot ( around 3/4", tapped down, and it's surrounding area is coated with a spray-on damping material, the sides of the enclosure have been drilled out at various intervals and filled with epoxy/lead shot). You'd think it would be fairly dead but that really isn't the case. It seems that the shot hasn't "dealt" with the vibrations caused by the spinning motor in this instance. It has "re-directed" them. IMO.
I recently tried three Stillpoints Minis (directly under) this enclosure and was not at all impressed. The vibration/resonance was brought back up through the enclosure. I then decided to use the brass cones that are bonded to the bottom ( the original design) for the "drain" needed to deal with the fact there is a motor spinning in this application. This was the better coarse of action.
It's all about the best way for built up energy/resonance to be drained while the materials used/their "end sound" and the application of these materials that matters, as I see it. This is what Richardkrebs is saying as are we all. We have differing ways to get to the best sound. Ultimately, It will be our own listening biases that make the decision for us. Thanks for the responses!
(As an aside, my current speakers Usher BE-718 have their internal side walls lined with lead plating. I'm happy with the sound and have not tried in any way to put my own imprint here on their sound other than speaker stands.)