Dual Ports: Port Length Question

Discussion in 'Home Theater Projects' started by Brad Boydston, May 30, 2004.

  1. Brad Boydston

    Brad Boydston Auditioning

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    On Adire's website, the Tempest in a 194L vented alignment requires two 3" flared ports five inches long. Using Unibox, I plug one port of 3" in diameter, I get five inches. When I plug two ports in, it reads two 3" ports each 12 inches long. Which is right and why?

    The larger the diameter port, the longer the length required. With two 3" ports, you're basically using a 6" port. When I plug a single 6" port diameter, I get 24" which is the same as using two 3" ports of 12".
     
  2. Patrick Sun

    Patrick Sun Studio Mogul

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    Actually, using two 3" wide ports is closer to using a single 4.25" wide port. You actually have to do the surface area calculation for one port, multiply by 2, and then solve for the radius of the single port with the same cross sectional area. Simply assuming that two 3" wide ports is the same as a 6" wide port is not the way to go.
     
  3. minhG

    minhG Stunt Coordinator

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    also remember that when you used a flared port like the ones adire recommends, the flares also add to the length. adire's suggestion is for the center section to be 5 inches, i think the flares add another 5-6 inches to the total length,
     
  4. Patrick Sun

    Patrick Sun Studio Mogul

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    The rule of thumb with those precision flared ports is to make the end-to-end length 1 inch longer than what's needed to hit a desired tuning frequency for the enclosure. For example, if you need 11" for your port length, then you'll need 12" for the flared port overall length, measured from end-to-end.
     

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