recommendation for turntable vibration damping

Since you have access under the floor, you can support the area directly under your turntable by shoring up between joists and the earth.

Believe it or not, cheap automotive scissor jacks work very well. Put a couple of cinder blocks or concrete paver stones on the earth, put the scissor jack on top and twist the gears until it snugly contacts the beams.

Better yet, if you have room to pull a 2X2 or 4X4 through the scuttle hole, you can drag that over to where the joists are (under the turntable) and bring the jack up snugly against it.

Even a slight bit of extra support will make a world of difference. I have these under my floor, purchased a half dozen cheap jacks at Pep Boys automotive and did it myself.

Target wall mounted turntable shelves are simply the way to go.

Damping your turntable's chassis is so trendy but few realize it can also suck the soul out of it. Try the wall mounted shelf first; It's cheap and EXTREMELY effective!!

You might be able to use a wall mounted shelf ala Target.

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
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Thanks for all the thoughts so far. It sounds like getting into the crawlspace is going to be the most effective solution for reducing vibration from the footfalls.

It also sounds like the wall-mount option would be a good bet...although the quick search i did didn't turn up anything that seemed big enough for an original Aries TT. The walls around here don't seem the best...closing the front door firmly seems to cause things to shake. I wonder if it's 6 of one, half dozen of the other. after all, if i'm listening to music, i'm sitting down & not causing vibrations from footfalls.

Re: Damping the turntable's chassis...
I don't think this is what I was hoping for. Basically, I'd just like to give it a rigid support such that no vibrations are coming up from below the chassis. I don't wnat to "weigh down" the chassis or any such thing. Would a Bright Start Big Rock do that? I'm under the impression that it just limits vibration.

Thanks!

I'm also looking into/learning about the SRA products, but what I'm hearing so far is that dealing with the space under the floor is the biggest area for improvement, and everything else will not make much of a difference until that is taken care of.

For reference, my speakers are on heavy stands (w/ spikes), and it doesn't seem like they're really getting the vibration from the floor...so i wonder if part of this is just that the rack does not weight enough and the spikes are not penetrating the carpet/pad.

Thank you all! I appreciate your thoughts.