I put the steel ingots on my A.Cerat gear based simply on my version of common sense. The AC gear is very heavy and solid, but the top steel plates which are designed to be easily removable to expose tubes, ring like a bad cymbol when tapped. I assume this does not translate well to ideal audio and Stravos of AC confirmed the sound is best with the tops completely removed. (He also said acrylic would be better than the steel, but is not practical give the size of the span.). I don't want to leave the tops off because I'm positive a mouse would eventually take of residence inside the preamp.
Yes, it's not unusal to invoke mass-loading with the intention of damping a flimsy or poorly anchored top plate to prevent it from vibrating in sympathy with vibrations already captured. However, it's important to note that when mass-loading a top plate you're not just mass-loading/damping a top plate but you are actually mass-loading/damping the entire component chassis and quite possibly a few internals - if the chassis is torqued much.
In any case, with the 50 lb steel weights, it now makes a nice solid "thunk" similar to the sound of the solid chassis sides albeit at a much lower frequency on top than the sides.
Though it can provide some psychological comfort, I would caution against listening to the sound of tapping a chassis when dabbling with vibration mgmt as there usually isn't much if any sonic value associated with it. In fact, if the vibrations captured at the component are going to remain trapped at the component, I'd probably much prefer the chassis to resonate rather than the internals. As a side note, vibrating component chassis parts in and of themselves have no direct impact on the input signal's fidelity. Rather, it's what this unwanted mechanical energy does to the electronic internals that greatly compromises the input signal's fidelity.
Are you saying this use of mass loading is at odds (or working contrary to isolation)?
Yes, that is what I'm saying. We're talking opposing methodologies so in a sense mixing the two is like trying to develop a hybrid between light and dark, on and off, or hot and cold. IOW, by mixing the two methodologies you are creating a performance brick wall for each thereby preventing either one from being sufficiently executed to its natural completion. IOW, a lack of completion for either methodology will exist and at least with the coupling methodology will induce a very serious performance-limiting governor whenever it encounters a genuine decoupling section in the path. A methodology is only as good as its weakest link, right?
So when one is concerned about a top plate vibrating, we've already admitted that no matter what we think we've done to remedy a problem, somehow some way vibrations are still captured at the component and perhaps releasing its energy at an easily excitable location within - like a flimsy top plate. But when you mass-load / damp a top plate and potentially an entire component chassis in addition to you're otherwise attempting to somehow generally follow the isolation methodology, where are you hoping that energy trapped at the component will be released?
I've asked this several times before. What does an object become when it is sufficiently damped?
It's seems to me they can work in concert.
Sure, it can work and with some sonic benefit as many here claim. But any hope for real potential for sonics to soar are gone since when we hear any supposedly genuine improvement we're most likely to close the book on that chapter and move on to something else - rather than think it through any further.
I admit I find much of the discussion and marketing claims around vibration mitigation to often be contradictory and confounding.
Understood. It's a huge club - probably the biggest club in high-end audio since perhaps 99.5% of all particpants will claim they are of the isolation camp.
The Revopods which I use under the AC gear are described both as isolators and as damping devices which disband vibrations in all directions. They are based on pot bearing damping along the lines of what used on bridges.
They are certainly not based on coupling methodology.
I've not seen the Revopods but I'll bet dollars-to-donuts based on the design, materials, executions, etc they're closer to the coupling methodology (though inferior) than to the decoupling methodology. Just as are many products supposedly belonging to the isolation methodology camp. Like I said, it's a huge club and it includes designers, mfg'ers, dealers, distributors, reviewers, enthusiasts, professionals, etc. Even the jargon used is inaccurate most times.
You've realized some coupling benefits with mass-loading / damping. If you really want to see what the coupling methodology is capable of, try following through on the coupling methodology. You've already started down the coupling path by mass-loading / damping. The next question is, what's really going on underneath between the component and shelf? Then evaluate the interface between the shelf and racking system, then the interface between the racking system (and speakers) and floor.
IOW, to maximize the performance potential of perhaps any methodology, one must see it through to completion.