Sand Pits for Adults

Remember those things from nursery school? Well they can make a return to your house as they are brilliant as energy sinks when placed under your TT, CD, amps and whatever else you can think of. Once again this is a copy of a commercial product, the Bright Star Audio Big Rock Isolation System (believe it or not).

The drawing below shows the idea behind the design. The plinth sits upon the sand and is isolated from the box by a gap of about 5mm all the way round. They can be made any size to suit the equipment requiring isolation. Personally I would go for a minimum of 50mm of sand. Silica sand is recommended as it doesn't retain moisture or living organisms. Good results however can be obtained with non-toxic washed sand used in children's sand pits that has also been dried in the oven.

MDF seems to be a good material to use for its construction. I have used 12mm board successfully but again use your head if making a really big one. Sand is very heavy and one day you might try a lead sand mixture. Think of where you will support it - at the comers only on feet or evenly all over. Bear in mind that wood is porous and should be sealed against ingress of moisture with oil based paint, varnish, etc.

Play Sand has a specific gravity of 1.65. (each cc weighs 1.65g). Therefore a sand pit for a turntable having internal dimensions for sand of 55cm x 40cm x 7cm weighs about 25kg (15400 cc multiplied by 1.65). Bright Star make one for the VPI TNT that weighs 130 lbs! We have found that even quite sturdy tables become a bit wobbly with this much mass on board.

I know many people who have made one or more of these things and all have been amazed. TT users cannot believe the results. The drop in the noise floor has to be heard. Andy uses a marble slab in the top of his. We have not done comparisons yet. Another I know has one under EVERY item of equipment.

A sandpit will improve the sound of your system no matter how massive a support you are using at present for your TT or other vibration prone equipment which to my mind is anything but the speakers.

Addendum by Andy Nehan

Further to Stephen's note about sand trays, I can report that the material used to mount the turntable or other device on is important. I mounted my preamp on a piece of MDF on 2" of sand. As I would have expected there was an immediate improvement in sound quality, particularly in the bass. I then placed the preamp on a 1" slab of marble. Surprisingly the sound improved again, the speed being noticeably improved. On reflection this may not be quite inexplicable. The preamp is very heavy (50 Ibs) and MDF is far from rigid whereas marble is extremely rigid. I suspect that the difference in sound is caused by the ability of marble to spread the load more effectively when compared to MDF.