Vibration and Isolation

Thoburn · 14856

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Offline Thoburn

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on: December 23, 2011, 12:29:27 PM
I am building a sandbox platform for my VPI Scout II turn table. It will consist of a 3/4 inch thick mahogany box with a 3/4 inch plywood base that is 1/2 inch up from the bottom of the sides. I have a 3/8 inch thick piece of polycarbonate that will sit on top of the sand. Under the box I am either going to use small tire inner tubes or Vibrapods. I have read good and bad things about sand boxes. Have any of you Bottleheads used a sand box platform or know somebody that does. I would appreciate some feedback on any type of turntable platform experiences.

Thanks!

Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
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Offline porcupunctis

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Reply #1 on: December 23, 2011, 12:38:11 PM
If you have cats in the house, I wouldn't go the sandbox route.

Randall Massey
Teacher of Mathematics
Lifetime audio-electronics junkie


Offline Grainger49

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Reply #2 on: December 23, 2011, 02:15:23 PM
Have a look at this on Wardsweb's site:

http://www.wardsweb.org/audio/isolation_table.html



Offline Thoburn

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Reply #3 on: December 23, 2011, 05:59:26 PM
Hey guys.

We have a cat, but unless he can do his business in a 1/4 inch slot while balancing on a 1 inch ledge I think I'm safe. Actually, I plan to put very soft 1/4 inch tubing between the edge of the polycarbonate and the sides of the box. Mostly to keep any sand dust from escaping and fouling up my records and table.

Thanks for the link. I have read that one and a bunch of others. The only negative I saw (and I can't remember where) was a guy that dished sand boxes and advocated inner tube(s) under a piece of MDF with roller blocks supporting the turn table. It has very bad WAF, but probably works well.

I will try to post info and results on my sand box experiment.




Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline Grainger49

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Reply #4 on: December 24, 2011, 04:18:31 AM
   .  .  .   inner tube(s) under a piece of MDF with roller blocks supporting the turn table.

I can't imagine this staying level two hours in a row, much less two days in a row.

I do want to try Wardsweb's idea with the glass bead media.  The drawback is you have to buy a whole bag of it and use about 1/4 of it.

My cat sleeps closed up in the listening room every night.  I keep the turntables covered so she doesn't jump on them.  She has her own box in the room too.



Offline Thoburn

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Reply #5 on: December 24, 2011, 06:18:32 AM
Hi Granger,

I like the glass bead idea to. IIRC you live in Colorado. I'm in Washington state. If we were closer I would happily split the purchase price with you.

Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline Doc B.

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Reply #6 on: December 24, 2011, 07:40:30 AM
At Berkeley in the 70's we used a giant sand box on inner tubes to stabilize a holography setup that had to keep the vibration of the mirrors down to just a few wavelengths of the HeNe laser's output frequency for something like 13 seconds at a time in order to get a good exposure. The added challenge was that the laser setup was on the third floor of the building. One would set up a Michelson interferometer on the table and project the interference pattern on the wall, and then count how long the average period was before someone on the third floor would walk down the hall, close a door, or sit down at their desk and disturb the pattern. I thought it was pretty amazing that the thing worked so well.  IIRC the recipe was a 4'x8' sand filled table with inner tubes on top, with another sand filled 4'x8' box on top of that. I don't recall the top of the top box floating on the sand, I think it was attached to the sides of the box. Might have been a piece of slate from a pool table, or my old brain may just be embellishing...

Dan "Doc B." Schmalle
President For Life
Bottlehead Corp.


Offline Thoburn

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Reply #7 on: December 24, 2011, 06:24:18 PM
I have the box up and running. It took all 50 pounds of play sand to fill it. And I can say that it is definately worth the effort. Imaging is improved. The instruments are more focused and there is more 'air' between them. The sound is more detailed. I would say that just about everything is a bit better. Will try to take some pictures when the light is better.

Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline Grainger49

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Reply #8 on: December 25, 2011, 05:38:33 AM
Hi Granger,

I like the glass bead idea to. IIRC you live in Colorado. I'm in Washington state. If we were closer I would happily split the purchase price with you.

I'm in Knoxville, TN.  I expect the cheapest shipping would cost the price of a whole bag of beads.  But thanks for the thought.

Won't the sand settle after a little while?  I suspect the glass beads do too.



Offline Thoburn

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Reply #9 on: December 25, 2011, 07:06:14 AM
Merry Christmas Granger,

Here is a design where settling is discussed.

<<http://cognitivevent.com/sandbox.html>>



Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline Grainger49

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Reply #10 on: December 25, 2011, 08:25:32 AM
That is pRC's site.  He was an old hand here when I arrived.  He is a materials specialist.  He knows a lot about vibrations and materials.  

I'll consume it soon.  Thanks for the link!

Merry Christmas to you and yours!
« Last Edit: February 14, 2012, 11:01:40 PM by Grainger49 »



Offline Thoburn

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Reply #11 on: December 25, 2011, 10:59:58 AM
Here is the new rig.

Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline Thoburn

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Reply #12 on: December 25, 2011, 01:31:34 PM
Sandbox in relation to other gear.

Dynavector DV-20X2L > VPI Scout II > Musical Surroundings NovaPhonomena
Mac Mini > USB DACiTx
Stereomour > Lowther Medallion DX4 and Rythmic Subs
Monster Power HTS3600


Offline bainjs

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Reply #13 on: December 25, 2011, 11:33:25 PM
Grainger,

This may be a project we can share.  I've got the woodworking down, you can work on the design.  We could share a bag of beads.  I've also been wanting one for my Wadia iPod transport.

It's something we can discuss in Jan.

Joel

Joel Bain


Offline Grainger49

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Reply #14 on: December 26, 2011, 01:49:06 AM
Sounds good!

Thoburn, your sand box looks better than my old VPI base.
« Last Edit: February 14, 2012, 11:02:50 PM by Grainger49 »