Appreciate your insight. Excuse my lack of knowledge, but if my speakers (Spendor D9.2) are base spiked to carpet, aren’t they already effectively isolated?
No. Not at all. Not that a lot of people haven’t been misinformed into thinking this. The most common false narrative is that a spike is a kind of diode. Or it couples. The people pushing these ideas never can keep it straight and are immune to the illogic of their mutually exclusive theories.
I know this very well by the way having been one of them, thoroughly indoctrinated in this nonsense until the reality of it being BS was proven false by some very profound and obvious listening tests.
Isolation is pretty much only accomplished by springs. Been used in industry, science, engineering, now audio. Not just any springs however. We had one of the biggest loons in the field here hawking "super stiff springs" that were way to stiff to work properly. Consequently giving springs a bad name. Which was his goal. Everything he did was intended to screw with audiophiles.
Anyway, point is springs in order to work properly must be sized to the load. Ideally they will allow free movement in all planes and at a fundamental resonance of about 4Hz. Below that and vibrations will be transmitted to the component, but it won’t matter because only really large amplitude matter then and we don’t hear that low anyway. Above that where we do hear with great sensitivity springs filter vibrations, a lot.
So the trick is to use springs just stiff enough to result in the component bouncing on them at about 4Hz. This is effective isolation.
What happens then is the component still generates its own internal vibrations. But now the only thing vibrating is the component. So vibrations dissipate and die much faster. The result is easy to hear. Lower background noise for blacker background, and much greater detail, together creates a sense of improved dynamics.
On spikes what happens is the component vibrates, the spikes transmit this into the floor or shelf, which now that is vibrating, and like a bell rings right back into the component. Also vibrations travel all through the floor, up the walls to the ceiling, up the rack to the turntable or DAC, tube amp- all adversely affected.
Real easy to get a set of Nobsound springs, only $30, prove it to yourself. Which is what I did. Way better than anything else you will find, at least until you get up to Townshend which are a lot better but also a lot more expensive. Worth it. I always recommend try and learn cheap, proof of concept, then once you know what you’re doing go big if you want big. But you will be surprised how much improvement you will get from a couple sets of Nobsound. Then if you go Townshend, wow, whole other level.
Here's a quick demo using a seismograph showing how speaker energy that goes into the floor comes right back up into the speaker. Notice this is on a concrete floor. So much for the idea concrete is the answer!