You are right that steel stores much of the energy of its resonance but wrong in saying that a steel stand is like a "rock" when filled with sand, etc. Many rocks, such as granite ring also.
Actually, I am right. At least as far as the stands I used goes. Granite does ring, as does other solid stones of that nature. But loose sand is not granite and behaves very differently from granite depending on the type of sand, it's density, and any sort of filler mixed in with it.
My particular stands behaved like a very non resonant stone.
And, yes, this is very possible. If you look up Stereophile's review of the Rockport Antare and look at it's cumulative spectral decay plot you can see that it is possible to for something to be so inert that it is quiet to beyond the ability to measure it. This is how my particular stands were. Granted, I have working knowledge of physics and knew how to make them this way using cheap materials. (Ie. the right type of sand, filler, and density) But they were absolutely non resonant. At least to the same level as the Rockports.
I think you are assuming that we understand all that is going on in a proper speaker stand.
There are many things yet to learn in how we hear and a stereo's performance. But I would argue that stands are not one of them. The function is really not all that complicated. It serves a simple function. And we know enough about material science to accurately predict outcomes in performance.
Yesterday I stopped by my local stereo store and took a look at all of the speaker stands they had on hand. There were quite a bit, actually. And a very wide range in prices. From $200 to $2,000. Stands from Focal, Dynaudio, Sanus, Audio Physic, LSA, pARTicular, and more. And, just by looking at them I can tell you that I would not personally purchase any of them. They all had an obvious (at least to my eye) flaw. One may have been non resonant(ish) but be flimsy. Another was rigid, but rang like a bell. I left with a much clearer understanding of why people find such clear differences in performance of stands! I was actually astounded at how even the $2,000 stand had simple flaws that I would think any mechanical engineer or physicist would immediately identify. So, again, no wonder there is such a difference in people's experiences.
So I understand where people are coming from better. But I stand (no pun intended) by my assertion that 1) Speaker stands are not THAT complicated. And 2) they don't have to be all that expensive in order to be extremely high in performance.
Maybe I should just go into the speaker stand business. heh heh
