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Port Question

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  • Port Question

    Hi all,
    I wanted to make sure I'm remembering this correctly; If I want to convert from a round port to a rectangular (slot) port, I need to maintain the same air volume contained in the port to preserve the tuning point of the box, correct?
    Jay T

  • #2
    No, you need to preserve the cross sectional area and length.
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    • #3
      Yes, but you don't need to calculate the volume, just the area. WinISD for one allows you to change the port shape and area and then will calculate the required length. You just have to make sure the area is large enough to the port velocity within limits.


      • #4
        Thanks guys, I appreciate the quick answers
        Jay T


        • #5
          Just something to consider. In my experience slot ports behave a little differently to the standard tubes and I've found that the port has always had to be cut shorter than predicted particularly where a bend is involved.

          Coincidentally I've found the same to be true of 3d printed ports, again particularly with bends, tend to end up needing to be shorter than modelled.

          My working theory in both these cases is that the additional surface area in the slot port and the rough printed surface of 3d printed ports are creating greater resistance causing the port to behave as if it is longer.

          In any case you should be prepared to model, test and fine tune the port length for the desired result.
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          • billfitzmaurice
            billfitzmaurice commented
            Editing a comment
            Slot ports are different. Every port has a region of high airflow resistance that extends inward from the port wall by 1/4 to 1/2 inch, in effect making the area smaller. That's of little consequence when that region is small compared to the overall port area, but with a slot it can be a significant portion of the port area. When I do make slot ports, which is rare, I never make the smaller dimension less than two inches. A bend complicates matters further if there's no reflector, as the additional air mass in the corner adds to the overall port air mass, lowering the port resonance.