As far as the box construction material... I'd just use MDF. Very smooth surface to paint or whatever.
Sandbox Design Advice
I understand the recommended design is to build an open wooden box plus a loose lid (possibly granite) which is slightly smaller than the internal perimeter.
Fill the box with kiln dried sand, float the lid on top of the sand and then component on top.
Heavy duty sorbothane feet for the box.
There were a few design details i couldn’t find on the forum and so pl can anyone advise on:
- what size should the gap be between the lid and the perimeter?
- how deep the sand should be for a 52 kg power amp (114lbs in old money 😀)?
- i am going to use a carpenter to make it for me (pine?) and would like a professional finish in black - any suggestions?
thanks very much - advice is much appreciated.
30 responses Add your response
Bright Star used a space of about 1/2" between the floating platform and the outer box of their Big Rock. In that space was placed a length of foam, to cover the sand. The Big Rock was made of MDF, but I'd use something stiffer for the floating platform, like a layer of Baltic Birch and another of granite, with constrained layer damping between the two. Check out ASC Wall Damp. |
MDF might work but it’s not the most durable material. You’ll for sure have to depend only on the glue as it doesn’t have much strength without a lot of bracing. Another good choice would be poplar as it paints very nicely, much more strength than MDF and your carpenter can joint the corners instead of a butt joint or a miter that may open up. Another option would be to use Baltic Birch Plywood if you want something a little nicer. All depends on what you want to spend, but you’ll have more in labor by far over the material regardless. As far as the lid or base goes, that would be fine as MDF as I think the sand is doing all the dampening and not the granite. Do a multilayer sandwich base of MDF/Cork/MDF. You could also line the inside of the box with Dynamat before the sand. I would think a 1/8” gap (ea.side) all around would be adequate. With a hardboard material, instead of MDF, to make the box it will be better for attaching the bottom plate as well as your carpenter can do a rabbet joint so you don’t see the edge of the bottom plate from the sides. If you’re r going to hire a carpenter, a trim carpenter/cabinet maker and not a framer... do it right. Good luck. |
| Post removed |
| Post removed |
I used 4"W hardwood around the perimeter, and plywood for the top plinth and bottom. For the top plinth, I cut separate sections of plywood for each turntable leg, in order to prevent conduction of vibration across the horizontal surface of the top plinth. The subsections are separated by 1/2" and sealed from each other with soft weather stripping. I attached 2"x 2" aluminum angles to the bottom of each plinth subsection, in order to conduct surface vibration deep into the sand. IIRC, the alum angle idea was borrowed from Galibier, but I can't be sure of that. |
| Post removed |
For the sand, look for Silica. It’s a non-organic man-made product used in sand blasting. It comes in many grades (the size of each particle), from powder-fine to somewhat coarse. I used No.60 in my Bright Star Big Rocks, just the right grade imo. I found some at a local construction supply yard, less than ten bucks for a 50 lb. bag. If I remember correctly, the Big Rock was about 4 inches deep for the biggest model, half that for the smallest. |
https://systems.audiogon.com/systems/8367 Both the top and bottom shelves of The Solution turntable stand are sand boxes. There is no right or wrong way of doing it. Some features are in general better than others however. Kiln dried for example is going the wrong way. That's nothing but trouble for no benefit whatsoever. In fact it is the opposite- wetted with a small amount of mineral oil is much better. Its better in terms of vibration control, and way better in terms of neatness and dust control. This rack has been up and running more than 15 years with nary a stray grain. Try that with kiln dried. The concept you will find most useful is understanding there is no such thing as isolation. That is not what we are doing. Its vibration control. The main source of vibration we need to control is the component itself. This is the case regardless of what component we are talking about. That's why this rack works so well. Read the system comments. Every single bit and detail in the system contributes to the fantastic performance achieved. Wish you could hear it. You would be amazed. Seriously. Again, read the comments. The rack is as important in achieving this as anything else. Compact sand with just enough mineral oil to eliminate dust and help it keep its shape, that is all you need. An inch or three, anywhere in there is fine. The container in this case is concrete because a lot of mass helps. It simply takes a lot more physical energy to move a large mass than a small one. So the more mass the better. But solid concrete or granite, while massive, have the problem of ringing. Hit an undamped block of either one you will hear the ringing. This same ringing is imparted back into the component. This isn't theory. This isn't parroting, regurgitating, repeating nonsense heard elsewhere. This is actual trial and error experience. Don't take my word for it. Get some material, cut some pieces, try it yourself and see. Been there. Done that. How I know. Same goes for the shelf on top. Hard to tell from the pictures but if you look real close at #7 you will notice the smooth packed sand in the bottom shelf with pieces of plain old MDF sitting on the sand, BDR Round Things and Cones resting on the MDF. Vibration control in action. The Herron generates vibrations, BDR controls them, MDF and sand stop and absorb or dissipate that energy so it doesn't reflect back up into the Herron. Just what you want. Without the sand, if it was directly on the concrete, the sound would be more dynamic and immediate but with an unpleasant treble emphasis owing to the concrete ringing. There are of course better materials and better solutions, just none anywhere near as cost effective as this. If you want to do concrete like this its a bargain, all the concrete to build this rack was under $10. The most time consuming part is designing and building the molds. But one mold for three shelves, pretty good deal. The other big thing to keep in mind, other than isolation being nonsense, is that because the problem is vibration control then the details of each particular situation are important. The optimal solution for a rack like mine on a wood beam floor is slightly different than a concrete floor which is slightly different than putting a sand box on top of an existing cabinet. In always pays to look carefully at the site, its various material properties (metal or wood, floor or wall mounted, etc) as well as physical considerations. On the floor is best, and the higher it must be the harder the job becomes. Anyone tries to tell you "just do X" is leading you down the primrose path. The best thing you can do before building anything is try a few proof of concept trials. Its not necessary to build the whole thing in one fell swoop. In fact that is about the worst way. What everyone does, of course. But if you build a few test pieces, it can be as simple as cutting some 3x3 squares of MDF, acrylic, wood, putting them under your footers, see how they sound. Take a couple small containers, pack a cup of sand in, put the test materials on top. This is incremental conservative high success rate way to go about it. |
My Woody the Woodpecker iso stand employs a bed of perfectly round smooth glass micro beads, much slipperier than sand for greater ease of motion, plus viscoelastic feet and hardwood (bamboo) box to simulate the physiological characteristics of the head of a woodpecker, which is able to undergo rapid and extremely high negative g forces 1200 g without injury. |
I elevated the heavy sandbox on five large, relatively soft springs from McMaster Carr. If you find the correct spring rate for the mass of the sandbox platform, the sandbox oscillates at around 1-3hz resonance when touched. This insulates the turntable system from the rack and any earth-borne vibrations. The sandbox then acts solely as a dump for vibration propagated from the turntable. It’s a bit eerie to give the box a visible push while a record is playing, or furiously jump up and down on a sprung floor, and experience absolutely no mistracking or skipping. So far I've only used this approach with unsprung turntables. |
That is a good point and what I meant about understanding the details of your particular situation. Since there is no such thing as isolation its all controlling/tuning instead its important to understand that is what suspended tables are doing as well. All you're really doing is tuning or controlling the vibration down into a less bothersome range, like your 1-3 Hz. This is in other words the resonant frequency of your rack or box or whatever. If that also happens to be the resonant frequency of your arm, or your suspended turntable, oops, problems! One more reason in favor of unsprung tables. |
I've used Bright Star sandboxes for years.If I refill them ever I would choose lead shot or stone rather than sand.It's not easy to level.To thoroughly dry the sand I heated it on the stove in a large stock pot,stirring it and watching the moisture steam out.After cooling overnight it's ready to fill and level. If you go with birch a wood stain is one choice.There are some very interesting metallic or stone look paints available also. Good luck with your project! |
With regard to the filling, my understanding was that vibrations passing through the filler would cause the particles to rub together and the kinetic energy would be reduced through friction turning it into heat. If this is correct then the best filler would be the one with the smallest particles and highest surface area. I have no formal scientific education and the above is just me regurgitating stuff i have read elsewhere so happy to be corrected if it’s wrong? |
Hi friend, Can you please check these products it may help you: https://www.ojcommerce.com/badger-basket-covered-convertible-cedar-sandbox-two-bench-seats-natural-g... https://www.ojcommerce.com/badger-basket-covered-convertible-cedar-sandbox-99895 https://www.ojcommerce.com/kids-cedar-sandbox-wooden-sandbox-2-foldable-benches-by-naomi-home-40501a Thank you |