Port length? with double wall ?

Discussion in 'Home Theater Projects' started by Curt Badry, Jun 19, 2004.

  1. Curt Badry

    Curt Badry Stunt Coordinator

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    i am building the Adire Alignment enclosure.Everything including inside volume is to spec. the only thing i am doing different is adding a double exterior wall 3/4"MDF on the bottom where the driver/ports mount. So my question is. I have the FP3 flared port kits from Adire, so do i make the center tubes 11" like adire wants or do i now have to make them 11.75" to allow for the extra thickness wall. I am not countersinking them so they will sit ontop of the MDF. I'm not sure if it's the total port legth that matters or the amount of the port that is inside the enclosure.
    If anyone could clear this up for me that would be greatly appreciated.
    Thanks
    Curt
     
  2. Curt Badry

    Curt Badry Stunt Coordinator

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    i am building the Adire Alignment enclosure.Everything including inside volume is to spec. the only thing i am doing different is adding a double exterior wall 3/4"MDF on the bottom where the driver/ports mount. So my question is. I have the FP3 flared port kits from Adire, so do i make the center tubes 11" like adire wants or do i now have to make them 11.75" to allow for the extra thickness wall. I am not countersinking them so they will sit ontop of the MDF. I'm not sure if it's the total port legth that matters or the amount of the port that is inside the enclosure.
    If anyone could clear this up for me that would be greatly appreciated.
    Thanks
    Curt
     
  3. GrahamT

    GrahamT Supporting Actor

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    (1.5)^2 X Pi X 3/4" X 2 (ports) = 10 cubic inches

    I dont think you have to make any adjustments. I did the same thing with my Tempest. The tuning frequency is dependent on the port diameter and length and the net box volume. The effect of moving the port out is larger box volume, but only by 10 in^3. The tuning frequency shouldn't change much at all.
     
  4. GrahamT

    GrahamT Supporting Actor

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    (1.5)^2 X Pi X 3/4" X 2 (ports) = 10 cubic inches

    I dont think you have to make any adjustments. I did the same thing with my Tempest. The tuning frequency is dependent on the port diameter and length and the net box volume. The effect of moving the port out is larger box volume, but only by 10 in^3. The tuning frequency shouldn't change much at all.
     
  5. Curt Badry

    Curt Badry Stunt Coordinator

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    thanks Graham,
    that's what i'll do, i'll just leave the port length stock. I wasn't sure if it would change the freq. that much.
    thanks for clearing that up for me.
     
  6. Curt Badry

    Curt Badry Stunt Coordinator

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    thanks Graham,
    that's what i'll do, i'll just leave the port length stock. I wasn't sure if it would change the freq. that much.
    thanks for clearing that up for me.
     
  7. Arthur_King

    Arthur_King Stunt Coordinator

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    If the internal volume is the same, I was under the impression that you should leave the port length the same. Technically it doesnt matter if the port sticks out of the box a little or if its countersunk. There's a few people around that have "chimney stacks" on their subs cuz the port doesnt have to be fully internal. As Graham noted, you're adding a little under 10 cubic inches if you make it a chimney stack, which I doubt you'd want anyways. Moving 1" outward is not much at all.

    Daffy Arthur King
    with the brain of a duck
     
  8. Arthur_King

    Arthur_King Stunt Coordinator

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    If the internal volume is the same, I was under the impression that you should leave the port length the same. Technically it doesnt matter if the port sticks out of the box a little or if its countersunk. There's a few people around that have "chimney stacks" on their subs cuz the port doesnt have to be fully internal. As Graham noted, you're adding a little under 10 cubic inches if you make it a chimney stack, which I doubt you'd want anyways. Moving 1" outward is not much at all.

    Daffy Arthur King
    with the brain of a duck
     

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