significance of long ports?

Discussion in 'Archived Threads 2001-2004' started by Brian Dobbs, Sep 17, 2001.

  1. Brian Dobbs

    Brian Dobbs Ambassador

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    I can't seem to understand the significance of having long ports when making a sub. What exactly are the advantages to having a long port as opposed to a short port? Also, what significance does a wide 3 or 4 inch port have? thanks
     
  2. Patrick Sun

    Patrick Sun Moderator
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    Long ports may have problems with resonance (and causing the port to not function properly - as a mass of air acting as a form of resistance in the subwoofer enclosure). Try keeping the lenght of the port under 5x or 6x of the port width when coming up with porting options. Width of the port will factor in port noise (the smaller the width, the greater chance that port noise can emanate from the subwoofer under heavy volume.
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  3. TerryC

    TerryC Stunt Coordinator

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    Brian,
    I understand you are enthusiastic and will undoubtedly love your sub. There is a lot more to just putting a long port in a box or even a short one, also a lot more to just the diameter of the port too.
    The length and width of a port within a certain box size determines the tuning of the final sub design. Too high a tune and you get a boomy one note wonder and little driver protection below tuning. Too low a tune and you may loose out on valuable headroom in mid base frequencies. Also not having a wide enough port can cause port noise as the air is rushed out of the port, too wide a port and the port becomes super long to obtain the desired tune.
    You SERIOUSLY need to take peoples advice on this forum and or do some major reading of past threads. There is boat loads of info here if you care to learn. I hope you like your finished sub, if you do that is all that maters, but unquestionably you would have made a better choice listening to what the others here recommended.
     
  4. ChrisA

    ChrisA Second Unit

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    For what it is worth, the (4) Black Hole Subs have a 9.75 inch diameter port that is 36 inches long. Tuning is 14 Hz. I am 100% satisfied. The first pipe organ resonance is well above the frequency I use these subs for.
    Pipe organ resonances are destructive and cause a small dip in output. This is much better than if it were to cause a peak in output. In any case, the first dip due to pipe organ resonance is so far above where I use the Black Hole subs, it is not a factor. I use a 60 Hz, fourth order digital crossover (Meridian 861).
    The lower you tune, the lower the group delay FWIW.
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    Pictures: The Worm Hole Theater featuring the Black Hole Subs and Death Star Platform
     
  5. Greg Monfort

    Greg Monfort Supporting Actor

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    Hi Chris,
    What's a Death Star Platform?
    GM
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  6. ChrisA

    ChrisA Second Unit

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