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Old 10th April 2010, 06:24 AM   #1
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Default Suggestions for decoupling a two tier turntable?

Hi

I'm a newbie here and this is my first post.

I have been obsessing (there is no other word for it!) about how to get better performance out of my Rega P2. Having already upgraded the platter, subplatter and arm, the weakes link is now the plinth, so I've decided it has to go.

At first I thought it would be fairly easy to come up with something massive, inert and rigid enough to take the place of the existing particle board plinth, but after reading a lot of forum posts here and elsewhere it seems that mass is not the solution.

Back to square one.

I am now thinking of a two tier system, with the upper plinth supporting the bearing and arm, and the motor assembly mounted beneath it's own plinth.

I have in mind using composite layers of material such as aluminium, rubber and 3mm mdf to build the upper plinth. Not sure if I should proceed the same way with the lower deck, but time will tell.

What concerns me most is how lock it together and still achieve optimal decoupling. I have heard of people using spikes and cones, but not really sure how this would work. Obvioulsy I want to avoid any lateral shift.

Currently I am thinking of using some form of rod, bolt or dowel as a locator, tightly fastened to the lower plinth, but with the upper just resting on it to avoid lateral movement.

Im wondering if anyone has any ideas on this or other methods I could try.

Thanks in advance

Sean
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Old 10th April 2010, 09:29 AM   #2
Spica is offline Spica  Canada
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I had similar thoughts, but I'm nowhere trying them out yet. I was considering a layer of sorbothane or similar between the plinths. The top would be secured to the bottom with bolts going through a hole larger than the bolt so it doesn't touch the lower plinth, and a sorbothane washer would then decouple the bolt. I have no idea if this is feasible, just an idea.
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Old 10th April 2010, 04:01 PM   #3
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Quote:
Originally Posted by Spica View Post
I had similar thoughts, but I'm nowhere trying them out yet. I was considering a layer of sorbothane or similar between the plinths. The top would be secured to the bottom with bolts going through a hole larger than the bolt so it doesn't touch the lower plinth, and a sorbothane washer would then decouple the bolt. I have no idea if this is feasible, just an idea.
Ahh yes, sorbothane. I have experimented with it in a variety of applications, and I can safely say it is NOT the material to use for decoupling. Its good for mechanical grounding since it is highly compliant - if anything it is useful for coupling rather than decoupling.

I like the idea of using bolts as locators. Have been thinking about ball bearings also.
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Old 10th April 2010, 10:16 PM   #4
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When using Sorbothane to isolate you do have to do some math and work out what surface area, durometer rating and thickness or material you will need to isolate at the required frequency. You can't just drop any old slab of it under a part and expect it work right across the audible range, that's not what it does.
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Old 11th April 2010, 06:13 PM   #5
Geosto is offline Geosto  Netherlands
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You can also use a piece of radiator hose.
In a similar way, you create a sub-chassis.
Click the image to open in full size.

Source
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Old 16th April 2010, 03:47 AM   #6
Nanook is offline Nanook  Canada
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Default sqash balls :)

use a nut/washer/bolt (or machine screw/washer/nut) through the top plinth, skewer a squash ball, go through 2nd plinth, add a washer, then a nut. Worked very well in the rehab of a knackered Roksan Xerxes. Very little tension (or none) is required as you tighten the nut, really it's there only to provide some sort of locating mechanism.
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Old 19th April 2010, 02:54 PM   #7
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Default Possible solution for decoupling

A few months ago I wanted to find the best way to decouple loudspeaker cabinets vibration and spoke with a fellow at Roush Engineering (they have a department involved with vibration and isolation control).

His suggestion was to use EAR grommets, which can be found in Michael Percy's catalog (page 19).
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Old 10th August 2010, 09:05 PM   #8
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Check this project out which sounds somethink likeyou are tryin to achieve

Split-Plinth Rega Clone Turntable


http://sdbhost.com/AudioPages/RegaDroid/DSC01619.JPG

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