Velcro as Acoustic Isolation?

Nope. Not even. What you want are springs. The easiest solution is Nobsound springs from Amazon, only about $30 for a set of 4. The way these work you remove springs based on component weight. If your speakers weigh less than about 75lbs each then you will be able to get by with one set by using the springs removed from one to create another.  

The harder and hardly any cheaper way is to hunt around for just plain springs, which you can probably find for under $30 for 8. The hard part being you have to shop around for the right springs based on size and loading. It can be done. I did it. They're mostly what's under mine. Its just very time consuming to find the right ones.  

Then there is the best by far solution which is Townshend. Depending on your speaker size you may want Pods but probably Podiums. These are springs too but much better engineered, much more easily adjustable, and sound quality that is far superior to any of the other options. They do cost a lot more but you definitely get what you pay for.

Actually, I think the way you're currently using it, it's acting more as a decoupleer.

I have thought about it but not very long.

I know we want to find inexpensive ways to accomplish our goals. Unless you're willing to try springs, I'm a fan of the Stillpoints SS which is a coupler/decoupleer all in one. Used isn't a bad deal.

You could set aside the marble for any added height the Stillpoints might bring.

Stillpoints on the used market are like a bank. If you decide to sell, you'll not likely lose much at all.

Yah, I'm more interested in the theory and application of Velcro as a energy sink.  I'm perfectly happy with my set-up.  With heavy duty Velcro, the surface area involved and mechanical interface seems to be a nice way to dissipate energy running through a system as an ancillary benefit.  Or maybe not...

It is a binder not a transmitter or isolator, maybe if it was hanging from Velcro. The space between the two surfaces the marble and the base of the speakers is just that a space... They are acting as isolation, but where is the vibration going? You want to transmit that away not store it in the enclosure.

By design, very dense material, with great dampening properties. Cast aluminum, HDS, Multi layer MDS. don't store vibration WELL. Think that way and things will change.

DEAD is not perfect for me... For the mids and highs..

I like a little MOJO, I get mine by the interior space, behind the driver, and usually highland wool, very dense. What I coat the inside of the enclosure with makes a lot of difference to.. Sound coat, rubber line, black hole... then driver dampening.. depends on how they are made.

Planars, round drivers, cast or punched baskets..

I use 390 lb pound HDF monitors, with 8" planars... very little vibration in that structure. There is no bass either...280 hz and down is CUT.

Bass columns, a little mojo.. There is an certain cabinet tone I look for..

Sub structures are different, green concrete... comes to mind...

Everything is different.. Everything makes a difference...Good or Bad, it makes a difference..

Regards

Velcro and marble to losing isolation items try Symposium.

oldhvymec I was supposing that vibration making it into the velcro would be largely dissipated as heat given the interface of the high surface area of the hook and loop fasteners.

Velcro dissipating energy as heet?

That concept is laughable.

OP I understand, most thing do dissipate energy as HEAT. Interesting, but again, I think it is dissipated by simple surfaces on the cabinets. 
A little different than you're thinking. It is measurable decay rate. Some go to great lengths to control that. The shorter the panels, and tighter bracing, the quicker the decay rate. That is what we want.  The inside of cabinets treated with sound coat, actually work on that principal.  Vibration is converted to heat, the cabinets work better, with a port and proper COOL air to keep the drivers at a given working temp..

The batting is another, place DIY and a lot of manufactures fall far short.. The batting in those cabinets, take a good long look at that alone. Three years I tinkered with liners, lining and  batting. From highland wool to heavy insulations. I put it in bags, with different, thread counts to multi layer bags. Nitrogen filled bags.  I tried all kinds of stuff.  Wool for the mids, HEAVY fiberglass for the subs and a lighter batting like poly fill for the MB.

One batting does not work for all, AT ALL, on everything correctly..
Like the Tinkers Titin says "for peanuts", compared to what we do outside the box..

Sometimes we do have to think INSIDE the box, not outside...:-)

Happy hunting.. good ideas only happen if you try.. Nothing wrong with that...

Regards

slaw friction...