DIY Isolation Plinth

Discussion in 'Hi-Fi Stereo Systems & Separates' started by kstandsteve, Feb 28, 2013.

  1. kstandsteve

    kstandsteve
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    Struggling to find the right sized plinth I have decided to have a go at making one myself.

    My TT is a Rega Planar 2 with various mods/upgrades.

    I am planning to sit the TT on a piece of Black Granite. I am also looking to upgrade the standard RP2 rubber feet.

    My question is regarding the feet - both TT to plinth and underside plinth.
    I was thinking of Sorbothene feet for one and spiked feet for the other - but which way round should they be for best performance?

    Cheers
     
  2. Mr_Sukebe

    Mr_Sukebe
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    Give them both a try and see which you prefer.

    I've heard a number of isolation methods, including:
    - Big heavy block directly on the floor (including concrete and marble)
    - RDC cones
    - Home made wooden cones
    - Full on racks like the ESS
    - Mana racks with glass on spike damping system
    - Target steel/wooden racks
    - Quadraspire racks - wood and also their pespex
    - Trichord damped racks
    - Isolation plinths (mission Isoplat I think), which basically use bike inner tubes with air in them
    - Still points - bit like a small pyramid with a high quality roller bearing system at the top, thus allowing horizontal but no vertical movement
    - Cushion. I kid you not, it's an alternatve. Used one between my old Meridian CD transport and Mana rack as the Meridian HATED my mana rack

    My experience are that it is ALWAYS kit dependant.
    I found the Mana worked great with Naim kit, awful with others.
    I've simply never found a real correlation, so you'll need to play.

    For reference, my personal preference on racks is the Quadraspire perspex solution, which does a wonderful job of soaking up vibrations.
     
  3. Doomlord_uk

    Doomlord_uk
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    And do you point the spikes up or down?

    Man, the questions audiophiles torture themselves with...
     
  4. robertseymour

    robertseymour
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    Spikes vs sorbathane is basically the difference between de-coupling vs coupling the TT
     
  5. windhoek

    windhoek
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    I'm a spikes kind of guy. I've got some Mana and the spikes sink in slightly to the boards below and each level is therefore 'coupled' to the adjacent level, except the top level of course.

    My only experience with sorbothane is with my TT. My TT, a Project 6 Perspex, has a sorbothane pad between the motor and plinth. I wondered what would happen if I put some semi-dense foam under the sorbothane and to my surprise, Lps sounded much better. Fwiw, the foam I used was roughly the sort of density of training shoe foam. You could pinch it easily, but it certainly wasn't as airy as say a bath sponge.
     
  6. Mark.Yudkin

    Mark.Yudkin
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    The question is do you want to isolate or couple? Typically TTs would be isolated, speakers coupled, since you don't want the stylus to skip when you jump on the floor, and don't want the speaker to move in opposition to the cone.

    Black granite (with spikes) will couple. The Rega Planar's rubber feet isolate.

    If you have a problem with the TT's stylus mistracking due to vibrations carried through the floor - a typical problem with wooden, but not with concrete floors, then the real solution is to mount the TT to the wall using sturdy shelving, thereby removing it from the floor's influence. This will yield more than any amount of isolation can ever achieve.

    If the real solution is for some reason not feasible (e.g. the TT must be placed in the middle of the room), then Mr_Sukebe has listed various options.
     
  7. kstandsteve

    kstandsteve
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    Cheers guys - sounds like a can of worms :)

    The turntable at present is sat on a timber fitted unit - quite sturdy, so a rack of any sort isnt what I need. My idea of the plinth was based on the isolation plinths currently on sale from the likes of Isokinetic (spelling?)

    The floor is suspended timber but these days I dont really dance around anymore and skipping due to floor vibrations has never been a problem.

    From an aesthetic point of view I favour spikes between TT and plinth and sorbethene feet under the plinth but that just seems wrong way round (?)
     
  8. kstandsteve

    kstandsteve
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    Doing some reading up on web it seems granite isn't the best choice. Might change it to 20mm acrylic
     
  9. lazarus

    lazarus
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    Ive been experimenting with this too. i bought 4 cheap acryllic sheets and little sorbothane feet for each corner and was impressed with a subtle change in the sound under my cd player.
     
  10. Mark.Yudkin

    Mark.Yudkin
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    If it's about aesthetics, then I suppose spikes plus sorbethene feet look suitably high-tech. If it's about sound quality, then you should be wall-mounting if it's in any way feasible.
     
  11. dogfonos

    dogfonos
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    Just in case anyone with a suspended subchassis turntable is reading this thread and thinking along similar lines, I'd advise against introducing any additional compliance as there's a high chance of ending up with an unstable setup where the two suspension systems interact with unpredictable results.

    Unless you've gone really OTT with the modding, the Rega Planer 2 is a rigid design (discounting the very small amount of compliance in the rubber/polymer feet) so I doubt you'll have suspension interaction issues but I wouldn't spend much on this experiment as the likely results are anybodys guess. Why not try squash balls - cut in half - for the compliant feet.

    I'm not sure that a record player coupled or decoupled to high mass is the best solution. I'd opt for wall mount too using a light, rigid shelf - unless you have 'problem' walls.
     
  12. MikeFaulkner

    MikeFaulkner
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    Got to say, i noticed a huge difference when i took my TT off my stand and put it on a shelf. I'm in a Georgian property and the suspended wooden floors are great at transmitting vibrations.
     
  13. Doomlord_uk

    Doomlord_uk
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    Granite is a cheap and readily available high-density and therefore high-mass material. It adds mass to your setup, damping vibration by increasing inertia. It also doesn't flex, of course.

    I have no idea what good acrylic will do - it's more flexible (barely) and much lighter. Acrylic is a popular material for use as a *platter* as it is supposed to have a similar mechanical impedance (if that's the right term) to vinyl and thus helps to ground vibrations that might directly cause the record to move...... but using it to support the whole turntable? I'm doubtful about that, to say the least.

    Wall mounting makes sense, if you have solid masonry walls.

    Supposedly one of the best supports is a partially-inflated bike inner tube...
     
  14. MikeFaulkner

    MikeFaulkner
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    So this makes me wonder, Is there a way to actually measure vibration? I mean most of us take isolation seriously, but how much difference would the likes of bike inner tubes or pipe lagging or indeed even isoplats make to the average installation?

    10%? 25%?

    In my case i noticed a difference in putting my TT on a shelf, but would i notice a difference by adding an isoplat or the like?
     
  15. Jim Pittsburgh

    Jim Pittsburgh
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    A couple of thoughts... first, there are a few Lenco based web sites that address this issue in depth, you might want to review those...

    the bottom line seems to be that mass is not the answer resistance to vibration is.... so granite/ marble etc don't seem to work on their own, the idea of using multiple materials is what seems to work.... I did a lot of investigation and expermentation on my own set up and found a low cost solution using industrial belting. Belting is made like car tires with lots of different compositions including cording or steel strands. .... I can help with sourcing it in the US.... send me a message.
    http://www.musicianshotsheet.com/news-reviews/spotlight/gear-porn/138-adventures-in-audiophilia-a-word-about-jitters.html
     
  16. Doomlord_uk

    Doomlord_uk
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    Yes, it's called an accelerometer :)

    However, if you can digitise your TT's output and look at it on a PC, you could do before/after or supported/unsupported tests where you just compare the music signals with and without a new support (or any other mod) and see if there's any difference - no difference obviously means the support doesn't work or there isn't a problem in the first place. If you had some software that could run an FFT sweep then you could look at the energy spectrum and see what frequencies are being stopped/let through... and tune your support system accordingly... I wouldn't know what software to recommend for doing this though.

    But this subject is eminently amenable to hard science - you just need someone with the ability and equipment to do it. Interestingly, a few years back Keith Howard did a two-piece article on this very subject... Part 1 established the principles and the background noise measurements. Part 2 was never published...! I bet because the science showed equipment supports either didn't work or more likely there was no problem to solve in the first place. Keith's rather technical articles were some of the best published in HFN; but as you might suspect, I think sometimes the facts risked getting in the way of the advertising revenue...
     
  17. kstandsteve

    kstandsteve
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    Doomlord - I based the acrylic idea on the isolation plinths made by Isokinetik and SRM who both use acrylic. I assume they have done all the testing and found it to work.
     
  18. Doomlord_uk

    Doomlord_uk
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    One would hope so. I'm sure it looks better than granite anyway :)
     
  19. daytona600

    daytona600
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    cheap Ikea Lack coffee table or expedit for rega + Lps
    expensive symposium iso platform £ 250
    or a full isolation rack for all your components
     
  20. Jim Pittsburgh

    Jim Pittsburgh
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    plinths - Audio qualia

    This is the site I was referring too, I suggest that you read this before you make up your mind about the proper material for your plinth. JMHO why re-create the wheel when you don't have too lol sometimes the web can be a wonderful thing!
     
  21. Doomlord_uk

    Doomlord_uk
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    ksandsteve - if you wish to experiment, and produce some reliable data in doing so, the best way to accomplish this is using the program Audio Diffmaker - simply play your record before and after you've added this or that support, tweak, mod or whatever and assess the results. All you need is a laptop or PC, you don't even need the accelerometer I suggested earlier - your TT is the perfect instrument for this already.

    Simples! :thumbsup:
     
  22. Tone-uk

    Tone-uk
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    +1
     
  23. Alan Mac

    Alan Mac
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    Quoting from the Audio Engineering Society (AES) paper presnted by Bill Waslo at the 125th AES Conventio in October 2008:

    “Tests using analog signal sources such as tape recorders or phonograph turntables are unlikely to be repeatable enough to be successful.”

    (The speed stability of a vinyl record is nowhere near good enough)


    Alan
     
  24. Doomlord_uk

    Doomlord_uk
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    Doh.

    Hmmmm. Wonder how we might work around that... It might be enough to show up the most obvious differences, at least? Anyone tried this?
     

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