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Decoupling a 80kg (at least) Monster Sub!

Discussion in 'Subwoofers' started by skeet94, Aug 12, 2005.

  1. skeet94

    skeet94
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    Ok I've done my searching and reading from previous posts, I still didn't get an answer to my little problem.

    I've got a 7cu.ft enclosure with a 13" JL Audio W7 series Subwoofer tuned to 18hz which weighs approximately 80kgs. It is a 5ft tall tower, hence I need it to balance properly. The enclosure is slot ported, with approximately 60square inches of port area and the port is downfiring with the subwoofer side firing.

    The enclosure sits behind a sofa, in a corner right now. With only 250wrms going to it, the whole house literally shakes apart, and this thing needs at least 1000wrms to reach it's full potential, so before I do actually put the power on it I want to decouple the subwoofer from the wooden, carpet covered floor. As it is right now the subwoofer does tend to get a bit boomy and is not related directly to the subwoofer itself or the enclosure, and as far as I can tell is due to the subwoofer being coupled to the floor. The enclosure is built like a tank, with it being braced in every possible way.

    My question is...

    How would I go about decoupling a monster this heavy? I was thinking multiple half squash balls with silicone on the inside, but then the whole thing would be sitting on balls, hence I'm a bit suspicious that it would be unstable.

    I've heard of Marble and/or Concrete slabs being used but not heard of any positive results.

    Anybody have any suggestions?

    Thanks,


    Mitul.
     
  2. eviljohn2

    eviljohn2
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    Depending on how your house is built, how about suspending it from the ceiling? :)
     
  3. Nic Rhodes

    Nic Rhodes
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    Auralex Gramma or what ever they call it now.
     
  4. Nimby

    Nimby
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    You are probably dead right about stability if it's balanced on tip-toe. But is it really necessary for it (the colossus) to stand up? Low frequencies are almost completely omnidirectional. So they won't know if they are lying down or standing up as long as you don't block the ports or driver. Lying down with some halved sponge rubber balls underneath sounds an obvious solution. Providing it is feasible in your room. Just give the port(s) and driver plenty of room to breathe.

    The boominess is quite possibly the present corner position. I'd be laying it down and moving it around behind the sofa while checking back at the listening position to hear if it affects the sub's sound quality.

    If you have an SPL meter you can do a response curve from your listening position using downloaded tones from <snapbug>.

    http://www.snapbug.ws/sinewaves/

    Have fun :)
    Nimby
     
  5. Joe Fernand

    Joe Fernand
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    Skeet94

    You'll need something 'Industrial strength' - air or magnetic may work!!!

    Lots of options - do a Google; 'isolation mounts heavy duty'.

    Best regards

    Joe

    PS Alternatively simply purchase/build a sub that actually works in your room :)
     
  6. Nic Rhodes

    Nic Rhodes
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  7. skeet94

    skeet94
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    The subwoofer works well in the room, for a DIY jobbie it easily outdoes majority of subwoofers out there in the £2000+ range. I just want to get rid of the vibrations on the floor hence it'll most probably get rid of the boomyness too. In the seat I sit in, the bass is tight and accurate, it's just elsewhere in the room it's a bit "boomy", it's taken me a whole week of playing with this monstosity to put it in the position it is in now. Thanks for the help so far...

    what would you say about thick rubber mat(s)?
     
  8. Nimby

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    The cheapest sub you'll ever own is the one you have already. ;)

    If you really want to try the upright position you could get an oversize concrete paving slab (for increased footprint stability) Bung a halved ball under each corner before struggling to get the sub up on the slab. :rolleyes:

    AV is not supposed to be this difficult. It's actually supposed to be fun. Unless you're a weight lifter? I just hope this thing has handles? :devil:

    Nimby
     
  9. Nimby

    Nimby
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    The problem with mats is they don't really compress when the load is spread over a large area. They act more like hard solid objects. Small and soft is far more beautiful in this case. :D

    Nimby
     
  10. skeet94

    skeet94
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    Thanks Nimby, I'll definitely try that out this weekend :D

    Trust me it was fun moving it around lol...had no handles then, still doesn't but will do later on in the month. Still need to finish it off with some sort of veneer, but thanks again for the help everyone.
     
  11. Nic Rhodes

    Nic Rhodes
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    Whats wrong with the Gramma? :lease: It is designed to do just this job, what you are describing is bread and butter to this device.
     
  12. Nic Rhodes

    Nic Rhodes
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    many of us with big subs have been there, tried the carpet, cork, marble, concrete, donuts, squash balls etc etc, Non are as effective as the Gramma
     
  13. Godfather

    Godfather
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    Nic, if it's any consolation I'm also baffled why your suggestion was totally ignored!
     
  14. Nimby

    Nimby
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    Perhaps skeet94 simply wants to try a cheaper option first?

    Or the sheer size and weight of the colossus suggests something more substantial or having a larger footprint than the Auralex Gramma. :)

    If I had a quid for all my posts that have been completely ignored I'd have a much better system. :devil:

    Nimby
     
  15. Ian J

    Ian J
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    There is some speculation as to the credibility and integrity of the manufacturer. There are "customer quotes" on the page that Nic linked to and not only is only one relative to subwoofers (with the other three being relative to guitars etc for which this product was designed) but that particular quote was severely overhyped, later proved in independent tests to be a gross exaggeration and worst of all was from one of their dealers with a financial interest in promoting the product and not the independent testimonial that it was portrayed to be.

    Many people just prefer to avoid products that are tainted in this way.
     
  16. Ian J

    Ian J
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  17. Nic Rhodes

    Nic Rhodes
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    Yes all very good politics but the Gramma does work. It is the only product designed to isolate subs from the surrounding building that I have found that works. When I had access to accelerometer I happily provoved this. 80 kg is a doddle for this device, doesn't even sweat at this.

    If he wants to spend less money fine, I can buy that, we have all been there, see my list of stuff above. None are as good, but some are faily decent infact, but none achieve what the Gramma does.

    Re Integrrity of the manufacturer, news to me, my contacts in the pro arena swear by these guys. I have found them nothing but excellent. In fact I would have them in the top flight of manufacturers. Henry might be able to add more as a 'big' user.

    This device works, if you want a DIY solution, fine but be under NO illusion this device works. Just take you meter to the next room and measure......
     
  18. eviljohn2

    eviljohn2
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    I havn't used the Gramma platform but I do have some Mopads beneath my subs which act are made of the same Platfoam and the material does work very well indeed. :)
     
  19. S H A D O

    S H A D O
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    The Gramma works for me. It's effectively killed all my "room" rattles.
     
  20. Nic Rhodes

    Nic Rhodes
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    EvilJ

    same basic material, as is the Platfoam, they all work well :) Another Mopad user here....
     
  21. Ettepet

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    I was a sceptic, using squashball halves under concrete slabs, but the Gramma seems to do things better. I have two Gramma, bought at a local powerbuy, for my 90 kilo sub (SVS Ultra/2).
     
  22. Godfather

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    My HC room is in the basement with a carpet covered solid floor so the Gramma doesn't make a huge difference as a subwoofer isolator. In my mother's flat where she has a suspended wooden floor, placing a single Gramma under a Velodyne CHT10 noticeably improves the bass. It simply sounds tighter with less overhang. I think without the Gramma the subwoofer was exciting the floor which created a sound of its own, adding distortion.

    I like Auralex, both the company and their products. Their support staff are very knowledgable and helpful. Their products work very well, exactly as described. The prices are IMO very reasonable, even in the UK.
     
  23. General Skanky

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    I've been quietly watching this stuff from afar and Nic's comment has swayed me.

    I may well tip my toe into these waters and see for myself.
     
  24. skeet94

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    Apologies Nic, I completely missed your post :). Didn't mean to ignore you.

    I was at work whilst reading/posting on this thread so couldn't read through it properly just read the last post and went from there.

    Come to think of it, I just hope the Gramma does work, cos I'm heavily considering it. As soon as I pick it up I'll post up my impressions of it.

    Thanks again everyone, apologies about not replying earlier. Just been busy with work and personal life is a bit hectic.

    Thanks,

    Mitul.
     
  25. Nic Rhodes

    Nic Rhodes
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    I know the problems, too much to do, too little time. :)

    I use four Grammas, not because I make great claims over the sound quality improvements but they do isolate the building from the sub effectively. I have a wooden floor. You don't notice or measure any great difference in the room where you are listening but you do notice a difference downstairs!! Not silly money anyway.
     
  26. skeet94

    skeet94
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    Hey Nic,

    Just wondering from what you said about it making a difference in other rooms, since my HT is in the living room, I'm hoping to make the sound in the living room less boomier by de-coupling the subwoofer from the carpet on insulation on wooden floor, would the GRAMMA do that? Or would it just make it less "distracting" in other rooms?
     
  27. Nic Rhodes

    Nic Rhodes
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    Other claim great things re boomyness in the room for the sub and that is why they use them, I don't see any difference personally but I might just be deaf. I do notice things downstairs however. Each location is different (wood / concrete etc) and the effect will vary and it is therefore very hard to quantify what difference it will make without trying it. It is one device I have travelled with to see it's effectiveness elsewhere. My experience if different form others doesn't make it wrong, it is just they interact differently in different locations. What it is designed to do, it does seem to be an effective device.
     

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