Subwoofers and vibrapods?

Discussion in 'Speakers & Subwoofers' started by ChrisHeflen, Oct 21, 2003.

  1. ChrisHeflen

    ChrisHeflen Supporting Actor

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    My friend has a sub and a brand new big screen tv.
    He thinks the vibration causes the tv to lose it's convergence.

    Could this be true and if so would vibrapods work?

    His sub is about 4 feet from the tv, but maybe it is the sound and not the physical vibration.

    Sub is a paradigm pw2200 and a Hitachi tv.
     
  2. John Garcia

    John Garcia Executive Producer

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    Vibrapods will isolate the sub from the floor, but it will not stop resonant vibration. Can't really tell you if it will cause misconvergence, but I doubt it. RPTVs convergence may degrade over time, regardless of the sub. You don't want vibrapods on the sub, you want spikes.
     
  3. Chu Gai

    Chu Gai Lead Actor

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    I'd let that TV settle in for a while since it's new. If the problem is verifiable, then this may require a service call because as John points out, this really shouldn't be happening.
    IF you're going to go the route of vibrapods, it's not a simple matter of just buying a set and putting them under whatever it is. There's issues of weight, shape of the isolation device, how much it deflects and fwiw, one's better off with more smaller ones than three or four larger ones. Do a search on Sorbothane and you'll find some interesting info.
     
  4. Nick L

    Nick L Second Unit

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    Have your friend try moving the sub to a corner that's not close to the tv. If the convergence still moves, it's not the sub.
     
  5. ChrisWiggles

    ChrisWiggles Producer

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    Over what period of time is it losing convergence? Perhaps that would be a good starting point.
     
  6. ChrisHeflen

    ChrisHeflen Supporting Actor

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    Thanks for the responses.
    He said it is happening every 3-5 days. He has only had it a few weeks.
    I think Chu is right (again) and it needs to settle. He said the people he bought it from are coming back out to calibrate it but they did say it needed to run a few weeks first.
    It's his first modern tv so I think he's learning.

    As far as the vibrapods, forget it I guess.
     
  7. KeithYates

    KeithYates Auditioning

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    Skip the Vibrapods (or Mason Super-W's or Kinetics KIPs or whatever) and use metal spikes to couple the sub to the floor? Applications would include standard wood framed floor construction? So you want a rigid member between a vibration source (subwfr cabinet) and a tympanic membrane (the floor) because you think it's somehow a good idea to stimulate the floor to sing along sympathetically with the cabinet? Because you'd like more subwoofer radiating area and you can't resist the prospect of enlisting the floor itself to give you the largest, lowest-fi "driver" in your town? Ever used an accelerometer to measure the effects of this kind of floor coupling? It isn't pretty. Bell Labs worked on this in the 1930s (which is why decoupling speakers and subs from walls and floors has been de riguer in studio sound ever since). If you proposed this kind of thing among pro engineers, you'd be fired the first day. The physics hasn't changed in the last 70 years. Nor have the psychoacoustics. C'mon, guys, THINK!
     
  8. Andrew Testa

    Andrew Testa Second Unit

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    Keith, he didn't say anything about wooden floors. If he's on a concrete slab then a spike couple is the way to go. If he has wood floors on joists (not just on concrete) he can eliminate the sympathetic floor vibrations by mass-loading the sub base. Spike it to a big slab of (hopefully pretty) rock. Considering the mass of the floor/joist system I don't think a sub is exciting very much energy unless the construction has long unsupported spans.

    And yes, I can do the physics.

    Andy
     
  9. Chu Gai

    Chu Gai Lead Actor

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    Got a Bell Labs link for that?
     
  10. KeithYates

    KeithYates Auditioning

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    Fair comment. But first I asked the question: "Applications would include standard wood framed floor construction?" The rest of my post was predicated on a "Yes." I didn't address the issue of anything but a wood framed floor construction. In the consulting work we do, most rooms other than dedicated basement-level HTs have plywood subflooring on 2-by members or TJIs. In addition to the Mason and Kinetics items mentioned, the curious may want to check out Sorbothane isolators. In all cases be sure to use a size, durometer and quantity so that you get the natural frequency well below your sub's operating range,
     
  11. ChrisHeflen

    ChrisHeflen Supporting Actor

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    His floor (for the curious) is an above the garage "long throw" floor. It has a rubber surround edge and can travel 4" form peak to peak for the massive power handling it needs to have from the sub stimulating the floor.

    Come on you guys it's just a fricken standard house floor.
    If he did use spikes or pods I doubt he'd be wishing he'd kept the receipt for either.
    He also has a miniture Pinscher that barks.
     
  12. Andrew Testa

    Andrew Testa Second Unit

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    Chris, you're killing me here!

     

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