Stuffing and port tuning

Discussion in 'Archived Threads 2001-2004' started by VinhT, Apr 3, 2002.

  1. VinhT

    VinhT Second Unit

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    When stuffing a subwoofer enclosure to increase the effective volume, do you tune the port according to the perceived final volume or the original unstuffed volume?
     
  2. ThomasW

    ThomasW Cinematographer

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    Ported cabinets aren't stuffed they are lined. Sealed cabinets are stuffed.

    No the stuffing/lining isn't calculated when figuring the net volume
     
  3. Dustin B

    Dustin B Producer

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    Ok, Thomas, this is confusing the hell out of me.
    http://integra.cyberglobe.net/caraud...ces/fiberfill/
    1.4ft^3 ported box tuned to 42hz with now stuffing. Add 1.4lb/ft^3 of stuffing and the tune goes down to 34.2hz. Meaning the effective volume has increased to 2ft^3.
    And TV has stated rather large gains in effective volume in the SVS from glass. Something like 2.84ft^3 looks like 3.75ft^3 with a very thick layer of glass lining the tube wall.
    Or are you saying that the space boost in a ported sub is real, but just that you don't think they should be stuffed as it could interfere with port air flow?
     
  4. Ron D Core

    Ron D Core Stunt Coordinator

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    I usually design my boxes without polyfill, then just staple some to the walls just to help breakdown resonances. As for the lining or fill question it probably doesnt matter a whole lot. All the polyfill does is delay the time it takes for the wave across the enclosure. If you are running a really high excrusion driver in a small box, you'll want to keep the fill away from the port opening to keep it from packing itself at the port opening. Most home woofers require a large box and dont have enough excursion do create those kinds of port air velocities anyway. In which case, if you think your port is to short you can sometimes stuff some polyfill in it to "lengthen" it.
     
  5. Patrick Sun

    Patrick Sun Studio Mogul

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    Stuffing a ported enclosure will lower the overall Fb of the enclosure. Mine dropped from 16Hz to roughly 13Hz when I stuffed a 6 ft^3 enclosure with around 3 pounds of polyfill (IIRC) on Sunosub III.
     
  6. ThomasW

    ThomasW Cinematographer

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    Dustin
    If you're making a ported design, start by lining the walls. Then if you feel that the design might benefit from additional damping; then start by adding a wad directly behind the woofer. You can add as much as you want just don't block the port.
    My experience with ported subs is that lining is usually enough. I don't try to force drivers to function in an undersized cab.
    With ported fullrange boxes; I line, then experiment with a wad behind the woofer and elsewhere to tune the response to my liking.
    There will be a point where increasing the damping doesn't improve the sound, it simply drops the efficiency. At that point remove the last amount added.
    Understand that none of this is etched in stone. So play around and find a recipe you like [​IMG]
     
  7. jeff lam

    jeff lam Screenwriter

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    In the sonosub design I am using from Dan W. I asked him if I should line the walls or just throw the stuffing in. He said just throw it in there, it didn't need to be on the walls and it's ok to have the stuffing sitting on the back of the driver.
     

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