recommendation for turntable vibration damping


hi!
i recently moved into a new home and just completed a project to install insulation under the floor (in the crawlspace). this was done to save on heating costs, but i figured it would also help to dampen vibration from the floor. the floors themselves are fairly cheap with thin carpet over them. (we are likely to install hardwood floors in about a year or so.)

anyway, after the insulation project was complete, i noticed that if i tapped my foot (as in moderate footstep), i could see my turntable shake. i'm wondering what steps i could take to reduce this vibration.

here are some relevant details:
>> VPI Aries on a Bright Star Air Mass 19, sitting atop a...
>> Finite Elemente "Spider" rack built up about 24" with a preamplifier, CD player, and VPI SDS also on it/weighing it down.

the rack is modular (which has served me well during a few moves) and is lightweight.

i'm wondering what my options are for reducing vibration -- i don't think i can afford a big/heavy rack right now.

is something like a bright star 'big rock' advisable? i would imagine loading it down with sand would really weigh down the rack and, presumably, dampen vibration. (they're not cheap, though...especially for the size i need for an original aries. i don't have an outboard flywheel, but i may get one one day.)

i'm open to any thoughts.

thank you in advance.
ebalog

Showing 2 responses by sean

We had similar problems in my Father's house. I ended up using some cinder blocks on top of the soil as footers, four floor joist supports and the longest 4' x 4" that i could fit into the crawlspace. The 4 x 4 was used as a brace between the top of the adjustable floor joist supports and the floor joists themselves.

Using this approach, the cinder blocks lifted the joist supports away from the soil, reducing their potential for rusting. The cinder blocks are also not going to rot over a period of time. Some use wood here, but i wanted to avoid that. This also made the supports more rigid, as i didn't have to extend them up as high. This basically resulted in a double wall thickness for the joist supports over most of their length.

On top of that, the load was spread out across the four floor jacks. This reduced the potential for "sinkage" of any given support point, reducing the potential for the requisite adjustment at a later date. It also helped to equally stiffen and level the entire area of flooring on that side of the room.

I placed the supports in the area located behind his speakers and in front of the equipment rack. By placing the supports further out in the room between the speakers and the rack of equipment, it not only helped to stiffen the flooring for both the rack and the speakers, but also to break up the nodes that would occur over the length of the floor. It also created a rigid break-point directly from the flooring to the Earth between the speakers and the rack. This reduces the potential for large amounts of energy to be transfered between them.

If i can recall, i purchased all of the materials while they were on sale at a local Menards. The total was something like $40 - $50 at most.

One thing that i would suggest before attempting ANY of this. Examine the area where you intend to install the floor joist supports and bring a tape measure with you. Take good notes. I say this as you need to know the appr distance ( height ) that the supports will be required to traverse. There are different length floor joist supports, so this will make a difference in what you need to purchase. Don't forget to take into account the distance "eaten up" by the 4 x 4 ( or whatever you use as a brace across the joists ) and footers, as you don't want to have jacks that are TOO tall after adding these in.

One more thing. You need to see which direction the joists run under the flooring and design your support system accordingly. Rather than having one long support spanning across the area, you might need to do a couple of smaller supports. If such is the case, the tape measure will come in handy, as you can measure what you need, cut to size and then bring it down with you. You don't want to have to try to cut the braces to size while laying in a crawlspace, etc... Sean
>
Valve & vinyl: Better measure the distance between the TT's footers and the required spacing of the shelves on the wall before making that purchase. It would be a real pain to go through re-installing the new shelving in the manner that you described only to find that it won't work as planned. You don't want to ass-u-me too much on something like this : ) Sean
>