sub box has poly fiber lining

Discussion in 'OT Technology' started by Xeryus, Jul 22, 2005.

  1. Xeryus

    Xeryus New Member

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    Hey all.

    I just bought a sealed dual 10" sub box (Scosche). It came with "Poly Fiber Lining Damper" on the inside.

    What does that do? Ive never seen this done before. How would it impact the sound comming out?

    Thanks
     
  2. P07r0457

    P07r0457 New Member

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    you talking about pollyfill (white stuff like what's inside blankets)?
     
  3. e r y k

    e r y k New Member

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    makes the box trick itself that its louder.

    i used fiberglass insulation in mine
     
  4. Ronin

    Ronin Guest

    trick? :hsugh:
     
  5. XR250rdr

    XR250rdr OT Supporter

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    It is supposed to make it appear that the box is 10% larger. However I've never been able to tell the difference.
     
  6. edrox

    edrox A good man, and thorough

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    I think that depends on the amount of poly-fil used. Typically, as XR said, it is used when a sub is installed in a smaller enclosure. Since the air being moved by the action of the woofer takes longer to reach the sides and back, it is like "tricking" response to the actual dimensions of the box
     
  7. veonake

    veonake OnT poster, OT lurker

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    As edrox said, if it is polyfill, it slows the sound waves down so that it gives the impression of a larger box than it is in reality. You can overdo it though and degrade sound quality. Almost all speakers contain some version of polyfill. In addition to making the box appear larger, it has damping characteristics and will also help remove box resonances. If yours simply has a lining of dampening material, its purpose is self-explanatory. It damps the enclosure to remove some resonance. I'm not sure if you know what resonance is, but it's not a good thing.
     
  8. Ronin

    Ronin Guest

    resonance is almost more annoying than shit rattling to me :mad:
     
  9. veonake

    veonake OnT poster, OT lurker

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    Isn't rattling usually a form of resonance? I.e. the sound is exciting the material that is rattling into it's natural resonant mode? I guess the difference is rattling is usually thought of as two different objects coming together to make noise, where resonance is usually thought of as vibration from one solid object, like a speaker cabinet.
     
  10. Ronin

    Ronin Guest

    a form i suppose, im referring to different types of annoying unwanted vibrations

    resonance usually refers to the intensification and prolonged quality of a musical tone created by vibration, the waves reflect and overalp upon one another.

    resonance to me is also similar to reverberation when sound continues after the source has discontinued and is like an echo bouncing off hard surfaces except it doesnt have that wave to overlap upon.

    i think another interesting distortion is when a standing wave occurs when a room size accomodates the wave length amplifying the sound :noes:

    I think rattling would be different mostly due to the fact it seems like an A to B to C step. Where A the sound vibrates B (lets say table) which shakes C (light plastic box)
     
  11. veonake

    veonake OnT poster, OT lurker

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    Well, you've redefined the word resonance then. I'm referring to it by its scientific definition. I apologize in advance if you already know everything I say next. Every material has a natural oscillatory modes. Every particle in the "system" oscillates in simple harmonic motion at the same frequency as the normal mode. I believe most materials have many normal modes. Theoretically when the driving frequency (i.e. the speaker frequency) matches the normal mode of the material (the enclosure) it will enter resonance and without increasing the amount of energy in the system, the amplitude of the resonance will increase an infinite amount. But, of course, that is in an undamped system, and no system is 100% undamped. Enclosures certainly are a damped system.

    So, rattling can be caused by resonance (i.e. the door is put into resonance and vibrates with enough amplitude to hit the door jamb causing a rattle. But, you could also just place your music so loudly that it vibrates the door enough to hit the jamb, even though it isn't vibrating in its normal mode.

    So, although resonance can have overlapping waves, this is actually what you are referring to as a standing wave. A standing wave is created when the frequency has a wavelength such that when it is reflected it produces constructive interference with a duplicate of this wave (such as a prolonged deep bass note), and effectively doubles the amplitude of the wave.

    Reverberation is as you described, but reverberation can also have its own standing waves, and it can be produced via resonance, but certainly does not have to be.

    I feel much more sure of myself this time, I wasn't really thinking about what was actually going on in my last post. So, in summary, rattling can be an effect of resonance, but you can have a rattle without having resonance. Resonance is more annoying, because it is often more difficult to fix than a simple rattle.
     
    Last edited: Jul 23, 2005
  12. Ronin

    Ronin Guest

    hm, well i certainly know more about resonance now :bigthumb:

    I checked some sources about resonance, perhaps I was misinterpreting them a bit.
     

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