Twisting a port?

Discussion in 'Archived Threads 2001-2004' started by Adam O, Apr 21, 2002.

  1. Adam O

    Adam O Stunt Coordinator

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    I was just curious if you needed a 30" port in your sonotube-based sub, but your tube was around 25" in height, could you use pvc plubing pipe and put together several pieces with u-curves in them to achieve this length? or would the curves in the port effect the sound??

    Sorta Like This:

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    Thanks Alot

    Adam
     
  2. Dustin B

    Dustin B Producer

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  3. Patrick Sun

    Patrick Sun Moderator
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    I did this for a smallish box that "needed" some extra porting length.
     
  4. Richard Greene

    Richard Greene Stunt Coordinator

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    To Pat:

    That picture looks like Reason #14 for using

    passive radiators rather than ports.

    I give you credit for having the courage to post it.

    Looks like it would take two days of using differential equations to calculate the volume and length of

    THAT port.

    Hopefully you won't take this post too seriously.
     
  5. NickSo

    NickSo Producer

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    I have 2 small question regarding port tubes...

    Does it make any difference if the lenght of the port is INSIDE the enclosure or not?

    And also, would having 2 ports that are say, 10" long each be the same as having 1 port thats 20" long? or at least move the air more efficiently?

    Just 2 smallq uestions, hope i haven't hijacked your thread
     
  6. Dustin B

    Dustin B Producer

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    For question one, no it doesn't matter.

    For question two no. There are three things that need to be considered in order to tune an enclosure to a particular frequency. What the net volume of the enclosure is, what the diameter of the port is, and how long the port is.

    As examples, assume the other two variables are kept the same.

    If you make the enclosure larger, the tuning goes down, make it smaller the tuning goes up.

    If you make the port wider, the tuning goes up, if you make the port narrower the tuning goes down.

    If you make the port longer the tuning goes down, if you make the port shorter the tuning goes up.

    Having two ports is like having a single larger port. But you can't just sum the surface areas of the ports though. The best way I've heard of to figure out what two ports will tune to, is to split the box in half and calculate with one port.
     
  7. Patrick Sun

    Patrick Sun Moderator
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    Nope, you can have the port on the outside of the enclosure.
    Richard, I was just playing around with an old enclosure and that's what happened! [​IMG]
     
  8. NickSo

    NickSo Producer

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    Ah, thanks alot guys [​IMG]
     
  9. Marc Bodin

    Marc Bodin Extra

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    There is no problem with putting bends in a port, as long as you know the total length and area of the port.
     
  10. Rudy H

    Rudy H Stunt Coordinator

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    Putting bends in might actually limit airflow a bit, but not much. I would avoid them if possible though.
     
  11. Patrick Sun

    Patrick Sun Moderator
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    But it's such a fun ride for that slug of air!
     
  12. ThomasW

    ThomasW Cinematographer

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    In theory ports should be straight. The resistance of the bends are different than that of a straight piece of pipe. It's a little complicated to calculate the resistance of the bends particularly if multiples are involved.

    Having said that I don't know if the differences actually translate in to audible performance issues. I've never bothered to make a curved port for a comparison.
     
  13. Patrick Sun

    Patrick Sun Moderator
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    So are we saying that when the port makes a "Wheeee!!!" sound, it's not having fun? [​IMG]
     
  14. ThomasW

    ThomasW Cinematographer

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