90 degree elbow question (ports)

Discussion in 'Archived Threads 2001-2004' started by Neil Joseph, May 18, 2001.

  1. Neil Joseph

    Neil Joseph Lead Actor

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    Real Name:
    Neil Joseph
    I cannot avoid having 90 degree elbows in my second sub (DIY) design. I am using PVC pipe for the construction. My question is this...
    When measuring port length (with a 90 degree elbow in there), do you use the average length of the elbow or the longer outside length of the elbow. I am assuming that since sound travels so fast, most of it will tend to speed around the outside longer dimension of the elbow rather than the shorter inner dimension of the elbow but then again, if you force water through it, the water will flow through the entire cross section of the pipe thus I would have to take an average length.
    Sorry for the dumb question and thanks in advance.
    orangeman
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  2. ThomasW

    ThomasW Cinematographer

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    Air is a fluid just like H20 [​IMG]
    Use the middle (average) of the elbow for your measurement
     
  3. Steve Hanna

    Steve Hanna Agent

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    Use a fabric tape to measure both inside and outside curves on the outside of the elbow. Add together and divide by two to get the midline length.
    Also, use a long sweep 90* ell instead of the standard ones. Two 45* ells if you can't find a long sweep in your pipe size.
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  4. Patrick Sun

    Patrick Sun Moderator
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    I must just toss in my $0.02 and say to avoid elbows in designs at all costs. I will out and out reject designs that require elbows. I tried retrofitting a boxed enclosure with elbows once, and just would rather not spend anymore time/energy/money on such a project in the future. But that's just me. [​IMG]
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  5. Dustin Haug

    Dustin Haug Agent

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    I didn't need a 90 deg bend in my design, but I used 2 45's to jog the ports away from the side walls of my enclosure. I haven't noticed any major sonic flaws with it yet. I've used elbows in several car audio subs due to having to cram some big ports in really tiny boxes, just measure carefully and you'll be fine. Straight ports are probably best if they'll fit your design, but ya gotta do what ya gotta do as they say.
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