Damping between shelves and sandbox

Try it with just the one thicker maple board.  Two boards and the additional interface probably create their own resonance problems.  This is something that can only be determined by trail and error.  Years ago I used a sandbox and found it was very effective, but I abandoned it because it was too messy.

ah yes, the old sandbox days
IMHO, these are easily bettered by replacing with Machina Dynamica Springs. They have various sizes to meet your needs. Contact Geoff for his expert advice. Oh and very inexpensive

hth

Check out the constrained layer damping product offered by ASC (the Tube Trap company), named Wall Damp. It's just what you're looking for.

Mix ordinary mineral oil in with the sand, just barely enough so it starts to stick together. It will stay put and for years. Mines over 15 years and dust free. Look close you will see its between the granite and the concrete on the top rack, and under the Herron on the bottom. https://systems.audiogon.com/systems/8367 
Those are also a couple ideas for your turntable. The top piece of granite is sold as machinist plate, comes in lots of sizes. I would not get such a big one if doing it again, but not about to change it either! You should hear the image this thing floats! Detail, dynamics, outstanding. 

A better solution than a big board, and certainly much better than cork, etc, would be four footers like what is under the Herron. Only I would make them round. I just never got around to it yet. But really its a matter of trial and error and testing. Its better to make three cheap easy versions and try them than put a lot of effort into one just because you think it will work.

One large board or shelf is in general not as good as four smaller ones. This is because most of the vibrations actually come from the component itself. A large board takes all that and starts to resonate and then that vibration goes right back up into the component coloring the sound. The exception is BDR Shelf, which being carbon fiber is dead quiet, dynamic as hell, and exceptionally neutral. But it is also very expensive!

I would suggest some test pieces of MDF in different thicknesses cut into circles or squares and several inches across. Level the sand, tamp them down and level, set the table on them and see how it sounds. You might also try similar size pieces of acrylic or stone such as marble, and of course various woods like teak or walnut, whatever.

If you do this one thing you will notice, once you have the pieces and before tamping them down, if you tap on them they will make a sound. Then what you notice is whatever sound they make when tapped, a little bit of that character goes into the music. That’s why a lot of guys like wood, it colors the sound similar to a lot of musical instruments also made of wood. Only they don’t realize they’re coloring the sound. 

MDF you will discover is by far the most neutral of all the materials you can try, with the exception of BDR. This combined with its low cost and being easy to work with is why its used so much. But you may find you like something else better anyway. Way it goes....

Whoa! That blows the dry sand theory all to hell. How about compressible fluids for the isolation? Oh, wait! We already have gas shocks and air springs!  And compressible metals! 🤗

@onhwy61 The thicker board is a bit wider than the sandbox, so I need to lift it a bit. It`s a really nice maple board, and I am satisfied with the sandbox, trying to keep the foundations. 
@bdp24 ASC`s solution looks good, I am going to contact them
@jab the surface is steady, it`s in a basement with concrete floor. The sandbox supposed to be a "sink" for the resonance coming from the TT. My integrated amp has it own sandbox also, but the board fits there.I found sand is -so far- the best solution for the base what fits my budget too. 
@millercarbon The mineral oil is going to do the job, good idea. What quantity you used for your box? I am considering between four footers, ASC or springs. I think it`s the best not to leave gap between the two boards or am I wrong?  I am keeping the board since it`s a really nice Shun Mook maple board, I really like it. I have tried granite, I think it was "ringing", but I guess I`ve messed up something. My phono stands on 5" MDF (6 layers glued and veneered) and thinking about to DIY it`s final sandbox soon. The bottom and the walls of the boxes are 2" MDF, but If I thought It would be good to upgrade later to real wood. Maybe I should drop the idea :) What footers would you use?
@geoffkait Would you set your springs in between two layers of maple? 
Thank you!

@geoffkait Would you set your springs in between two layers of maple?
Thank you!

>>>>Yes, that’s what my Promethean Base did for many years. Now with the smaller springs you can still place them between two layers of maple or directly under the component. If you use two layers of maple you should use cones under the component and cones under the lower layer of maple.

@millercarbon The mineral oil is going to do the job, good idea. What quantity you used for your box?

No idea. Too long ago. Just pour and mix, pour and mix. You're going for not even damp, just barely enough so the stuff holds a shape with no dust.

I am considering between four footers, ASC or springs. I think it`s the best not to leave gap between the two boards or am I wrong? 

Okay there's a couple things going on. One is the sand is adding mass and damping, but almost no stiffness. Its the board or whatever goes on top that gives the required stiffness. Otherwise without that its like sorbothane, horrible, sucks all the life out of the music.

Sand and mass stops most vibrations but not the highest amplitude lowest frequency ones. Springs will work for that. But springs bounce. So if you do have something like people stomping around you still need something to control the springs. They are at best just one more tool.

I am keeping the board since it`s a really nice Shun Mook maple board, I really like it.

Great. So keep it. I would suggest trying it laying directly on the sand. That way you get a little of the maple sound you like but not as much and with more slam and dynamics. But its all a balance. The more you try the more you will see.

I have tried granite, I think it was "ringing", but I guess I`ve messed up something.

No, you're right, it rings like a bell. Its awful. Mine is on packed sand inside a massive concrete sand box and that kills a lot of it. Tap it and instead of ringing its a short sharp 'tink'. Which is not as good as "tunk" but way better than "tinggg" which is what it does with no damping. Then there's multiple layers of BDR  and even so I have to use a couple different things between the granite and the BDR. Its a pretty good balance, super dynamic and detailed, and I have got it down to where no one ever even notices any ringing. In fact the verdict is "audiophile nirvana".  Read the last system comments. But that's the thing about striving for perfection. I would try something else if doing it today.

My phono stands on 5" MDF (6 layers glued and veneered) and thinking about to DIY it`s final sandbox soon. The bottom and the walls of the boxes are 2" MDF, but If I thought It would be good to upgrade later to real wood. Maybe I should drop the idea :) What footers would you use?

Yes I would drop the wood idea. Unless you really like it. Always do what you like, never mind anyone else. All the wood species I tried imparted a very characteristic sound. I tried them because other guys thought they sounded great. MDF has a much more neutral character. But then its also a tad less stiff, therefore a tad less dynamic. Always the trade-off. Anyway if you want it to look nice simply cover with real wood veneer. That's how these subs are finished, rosewood veneer. https://systems.audiogon.com/systems/8367 
Mine is from https://www.veneersupplies.com/categories/Raw__Wood__Veneer/Wood__Veneer__A__-__G/ and I used the one with adhesive backing. Cut, peel and stick! Could hardly be easier and looks terrific! 

(I know you could just scroll up for the link to my system. But someone complained about me posting links to my system. So now guess what? Even more links to my system.)

The springs don’t bounce, silly. The combination of springs and mass acts as a mechanical filter. You desperately need to head over to your local library and read up on mass-on-spring isolation, you know the same method of isolation that the project to detect gravity waves used. Gravity waves have amplitudes on the order of the diameter of a proton and frequencies that include very very low ones, so sand, oil, Sorbothane, carbon fiber cones, etc. won’t work to obtain the very great sensitivity of the detection system required. But springs will. The best isolation is provided when the ease of motion is the greatest. Ironic, huh?

You're just upset because instead of word salad I serve up information. Always in the back of your mind will be the knowledge it took me one post to understand you don't know what you're talking about.

Don’t worry, mc, your secret is safe with me. It’s protected by Audiogon teacher-student privilege. Everything is topsy turvy. Me topsy, you turvy.

use something like delft clay or petrobond casting sand. 

Maybe try plywood instead of mdf or solid wood. Works very well for me ... no tt experience though. Best plywood would be "Panzerholz" (I think it's called phenolic plywood in English). Very heavy, used for cars and trucks and tanks (Panzer in German), but very expensive too.

If you must use sand let the dry sand do the isolating but everywhere else you wan to use extremely hard materials so that energy is rapidly Evacuated out of the system.That’s why I eschew soft materials like Sorbothane and rubber and lead and relatively soft cones like carbon fiber and brass. Step up to the plate and get some hardened steel cones or the NASA grade ceramic cones from Golden Sound. Springs are a better solution from a SQ perspective, that’s why the sandbox guy at Bright Star went to springs a long time ago. Twenty some odd years ago to be precise. Hel-loo!

Springs just as goefkait said.
Preferably under a mass loaded shelf.

And put your loudspeakers on springs with a solid substrate underneath, it will improve EVERYTHING! Obviously finding the correct springs for the load they are bearing is important.

"IF", you mix any liquid medium with the sand. OR, it is simply very humid and the sand becomes damp. Either will totally negate the ability of the sand to act as a "transducer". Where the vibration causing the resonance problem changes from a "kinetic" energy to a "thermal" energy. The heat then simply dissipates into the ambient air. "This is accomplished by the friction, "Sand grain against the other vibrating sand grains" = heat. Induced by your gear.
 Constrained layer damping with  "Coupling/decoupling" between layers   works great and you may "Tune" it as needed.
 There is a reason that "Tone woods" are called "tone woods"! 
It is because of how they each handle different vibrations, or "Resonance" as they do. MDF is crap. It is dead, sawdust and glue.
The best has always been certain Mahoganies and Rosewoods but they are mostly illegal now to buy or just unavailable.
 Sugar or Rock Maple, Black Walnut and Cocobolo seem to cover the spectrum the best now for what's available. "Some" Mahogany from Costa Rica", "Santo's Mahogany". It is "Ok to good", but hard to find and you have to know the wood to pick it out. 
Dupont's, "Corian" works well though. But you have to play with the thickness. It is harder to get right than say, "Maple"..
 The gear stands I make start with a "Slab" I buy. Usually 2'to 4' wide. 16' o 20' long and at least 3-1/2" inches thick. "5" thick is best but very rare.
 Out of a slab I get 5-6 "Plinths". Once planed and squared and sized I add layers of Corian and then other woods as needed for the purpose. With springs, bearings, "sorbothane", and also assorted "Whatchamacallits", that have developed.
 Complete they are 3" - 8" thick. The ones I make with a "Void" for sand, shot or oil? Those are first sealed "Inside and outside", with two part "System Three", epoxy with an access that is sized to use an "Expanding rubber boot" to keep it sealed.
 No leaks and no dust.
 But "Damn" they are expensive. A raw "slab" of the hand-picked hardwoods, "Tone woods",  avg. about $2000 at my cost.
 But hey, "I figure that I'm worth it"! And they are fun to make!

Springs that don't bounce. Concrete floors that float. Scare quotes and "whatchamacallits".  

You have entered a land of mystery and imagination. The sign post ahead: You have entered the Audiogon Zone.

Your frogs have no wings?
 Perish the thought!

By the way...
 You can pick up a "Vibration meter", fairly cheap and then actually measure what is going on. Or make one even cheaper. All you need is an laser accelerometer array. Some mirrors and etc. That's what I did.