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DIY 'Gramma' platform

Discussion in 'Home Cinema Building DIY' started by Gary Lightfoot, Feb 18, 2004.

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  1. Gary Lightfoot

    Gary Lightfoot
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    I've had my Rel Q200E on a 1ft square paving slab which sits on two pieces of wood (18mm x 69mm x 290mm) which have some rubber stapled to them. I'm using it as an isolation platform of sorts to stop my sub from vibrating the loft floor too much.

    Out of curiosity, I bought a 'Gramma' isolation platoform to see how it compares.

    Structuraly, it looks like a 12mm piece of MDF with carpet stuck to it, and two strips of thick dense foam attached to the bottom. I've yet to see how it compares with my platform.

    The only other difference is that between the two foam strips, there's a filler of diamond shaped foam - I assume to somehow attenuate any soundwaves that may come through the mdf base.

    Looking at the construction, and provided the two types of foam is readily available at good prices, it should be simple to build one, and probably cheaper. I'll try to take some pics so others can make their own if they like - custom sizes would be relatively simple if you have a jigsaw/circular saw. :)

    I'm sure I've seen the foam stuff available from PC modding places...

    Gary.
     
  2. Ian J

    Ian J
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    One forum member made his own out of an old carpet and a wooden door but replaced it with a Gramma and subsequently posted........

     
  3. Gary Lightfoot

    Gary Lightfoot
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    Somehow I think I'm going to find less difference between my two isolators then. :)

    I was looking through the 'Audiophile Candy' catalogue - it's amazing some of the claims that are made about some of the products there, and I find most hard to believe.

    Green pens around CDs and mats on/in CDs etc. Burn in CDs for your equipment etc ... :D

    I think I'll glue some wood and carpet to my slabs, and sell them as HD 'Grammers' - I'll be rich!! ;)

    Gary.
     
  4. MuFu

    MuFu
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    Those are my comments above - virtually no audible difference from the DIY platform in this room, although raising the sub up using either had the effect of making it less boomy when within ~1.5m (not really beneficial for most people). Here're the plots I made at the time:

    [​IMG]

    Blue - sub on floor
    Purple - sub on DIY platform
    Orange - sub on Gramma
    Green - sub on Gramma + EQ

    The Gramma is *far* better at isolating the sub than the DIY platform was. That was worth the expense alone for me.

    MuFu.
     
  5. Ian J

    Ian J
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    I was talking to a chap recently who had just ordered a Gramma and he told me that he could hear the difference even though it hadn't yet been delivered. If it cost him money, he could hear the benefit :D
     
  6. Gary Lightfoot

    Gary Lightfoot
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    LOL - that's the best kind!!

    Seems the equaliser (BFD?) is the best way to go for audible effectiveness.

    I just wanted to reduce vibrations from the floor. I'll do a bare foot vibe test and take pics so you can see how blurry my feet are. ;)

    Gary.
     
  7. Ian J

    Ian J
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    Just make sure that you wash them first
     
  8. Nic Rhodes

    Nic Rhodes
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    The Gramma is VERY effective at reducing vibration to floors in particular wooden floors. It is audible better than anything else I have heard / built but the differences are 'difficult' to measure. It is one area I think where measurements (or at least my measurements) need to be much more sophisticated and I need to look at spectra rather than just levels. (This is in hand is the bloody supplier pulls it finger out re the new mic).

    For the cost of a Gramma I think they are a no brainer
     
  9. RichardH

    RichardH
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    Sounds interesting - where did you get them from?

    Gary - any feedback on the vibrational improvements from the Gramma?
     
  10. Ian J

    Ian J
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    They are available from Dolphin Music here at £59
     
  11. Gary Lightfoot

    Gary Lightfoot
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    Richard,

    I can't hear any obvious difference at all to be honest, but then I really didn't expect to. The graph above shows that I think, so it may only be measurable via my SPL. I haven't done the bare foot comparison because I now want to put the main stereo speakers onto my own DIY 'Grammas' so that I further reduce vibrations from the floor.

    I have to say that I agree with Beekeeper that for the price, the Grammas aren't that expensive to try.

    I can get hold of some similar high density foam rubber similar to the stuff the Grammas use to stand on, but I can also get some heavy duty open cell polystyrene stuff that is very similar. Any ideas how this would fair comparitively to the rubber?

    Gary.
     
  12. Smurfin

    Smurfin
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    what sub are you using Gary?
     
  13. Gary Lightfoot

    Gary Lightfoot
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    Hi Matt,

    it's a Rel Q200E. I'm thinking of trying something bigger or doubling the sub up just to see if I can increase the low end audibly. I'll probably try my Paradigm PDR 10 with it just to see what difference it makes.

    Will placing the two subs side by side on the same gramma make a lot of difference do you think, or shouild they be further apart?

    Gary.
     
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