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For years I've had a DIY sandbox with an MDF top under my VPI TNT 3. But I just significantly improved upon this set-up by cutting the MDF top into pieces to isolate all the subassemblies into the sand (e.g. motor, flywheel, pulleys, individual suspension towers.) Surprisingly, the greatest improvement came from isolating the suspension towers from each other. I conclude that even with sand dampening, there is lots of vibration transmitted across the top of the sandbox. Or perhaps decoupling the towers is just a better way to draw vibration out of the TT. Now that the plinth has been cut into pieces, it will be simple to test small panels made out of different materials (maple, granite)under the suspension towers.Makes me think the platform may be more important than the TT...
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I'd be very interested in your findings. I have a sandbox also, with a butcher block cutting board on the sand, another butcher block on top of that separated by 3" cork squares with rubber on either side, and the non-suspended TT on that. I find that a wrap on the sand box is still easily transferred through the whole assembly and is audible through the speakers. I would love to find a cure for that and improve the isolation. The cork and extra board helped a lot, but not completely.
With the stylus sitting on a stationary record, a wrap to the sides of my sandbox is completely damped out, but a downward wrap along the top perimeter edge of the sandbox is transmitted through the speakers. A wrap to the steel rack below the sandbox is also transmitted through the system. Transmission of vibration was reduced but not eliminated by cutting up the sandbox plinth.My next moves include marble or granite plinth material, and replacing the sorbethane sandwich in the TT suspension with solid material such as maple, brass, and springs. From there I might try a Machina Dynamics Promethean platform, which uses several plinths separated by springs and points to achieve resonant frequency of 2hz. The sandbox can be floated on the platform or eliminated.
I built the sandbox for a ScoutMaster with a separate box for the motor. I tried MDF for the platform, but wasn't impressed. It sounded somewhat dull. I then replaced it with a piece of Travertine from Lowes. To my ears it sounds better. You will need a wet saw to cut it since it is a stone product.
On another note, I just saw a sandbox that someone had built for his TNT in which he put concrete pillars in the sandbox under the 3 suspension towers (I think thats what they are called). It looked very nice and he was very pleased. I cannot remember the inmates name. I found it while looking at his system in his profile. You might go over to vinyl and ask around if you are interested.
Life has lots of trials and lots of music to help us through them.
I think that's why Brightstar Audio uses a very thin plinth for their sandbox top. I don't think it is made out of MDF either for the very reason of conducting the vibrations into the sand, not the plinth.
purchased the items to make myself a nice sandbox tonight! From what I understand it is one of the most significant improvements one can make for their TT... I have a SOTA comet on it's way to me to replace an ol' vintage dual.
Mike "use your ears" Z
Michael,After cutting up the top plinth I checked resonances of the subpanels with the knuckle test. Were I doing the sandbox over again, for improved absorption I would make the dimensions of the sandbox at least 4" wider than the TT on all sides. D
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