3" or 4" ports on Tempest Adire Alignment?

Discussion in 'Archived Threads 2001-2004' started by Scott Simonian, Jan 30, 2002.

  1. Scott Simonian

    Scott Simonian Screenwriter

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    I have finally decided on the alignment Im going for on my first DIY sub project. I picked the Adire Alignment. I definetly am using the Tempest.
    Anyway, the design calls for (2) 3 inch, flared ports on the bottom of the cabinet along with the driver. I would like to use (2) 4 inch ports.
    Im assuming Id get a nice reduction in compression, if it would occur in the first place. Can I expect this? Lets say I would get a worthwhile improvement, how long would the ports have to be now?
    They are originally about 11 inches long, tuned to approximatly 15hz.
    Second, would the 4" ports fit on the bottom? The space is pretty tight on the bottom. I guess I could just modify the schematics a little to fit the ports.
    [​IMG]
    Anyone know if they can help?
     
  2. Going from 2x 3"x11" ports to 2X 4" ports would mean that the center tube would need to increase by ~ 17" (if I did my calculations right
     
  3. James Slade

    James Slade Second Unit

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    I asked Dan this exact question because I was concerned about port noise. According to him there is no reason to use larger ports, at least wrt noise anyway.
     
  4. Scott Simonian

    Scott Simonian Screenwriter

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    Really? I trust the plans and I trust DanW. I just wasnt sure if I would even run into a compression problem with the design. I just dont want it to EVER happen. I hate compression.
     
  5. Kerry Hackney

    Kerry Hackney Stunt Coordinator

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    Scott,
    I have just completed the Tempest / Adire Alignment within the last two weeks. I built mine per the plans provided by Adire. I haven't heard any port noise of any kind with mine. I wouldn't worry about changing to 4". And I like the idea of having as much wood on the bottom as possible to keep everything stiff. If you did do it, you are correct in that it will be a very tight fit. The flanges for the ports are pretty big. I think you would end up having to modify them to get it to fit.
    I have checked the ports at different times with various material and you would have to be dumping huge wattage to get anywhere near a problem. At that kind of volume I don't think it would matter anyway. On music software you'll never get close. There just isn't that much content below 30Hz. Build it, you'll be amazed... [​IMG]
     
  6. Ryan Schnacke

    Ryan Schnacke Supporting Actor

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    With a 3" port the cross-sectional area is Pi * (3/2)^2 = 7.069in^2

    With a 4" port the cross-sectional area is Pi * (4/2)^2 = 12.566in^2

    That's an increase of 77.8% in cross-sectional area. Wouldn't the ports would have to be 77.8% longer? That's 1.778 * 11 = 19.56in
     
  7. Kyle Richardson

    Kyle Richardson Screenwriter

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    No need to increase to 4" and if you did you will run into port length problems for the size of enclosure. Stick with the 2ea 3" and enjoy!

    Kyle Richardson

    Acoustic Visions
     
  8. Scott Simonian

    Scott Simonian Screenwriter

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    Ok, Ill stick to the 3" ports. I cant wait til I build this monster.
    But if I hear a hint of port noise, Ill blame you guys. [​IMG]
    Im sure I wont run into the problem. Just thought it wouldnt hurt to make em bigger. I dont think it would be difficult to add a few extra inches to the port length. It will be a tall cabinet. Im probably wrong in any case, so dont listen to my babble.
    Now I just need someone to buy my current sub or give my $300. [​IMG]
    EDIT:
     
  9. Scott Simonian

    Scott Simonian Screenwriter

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    Anyone change their mind?
     

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