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It’s that time audio enthusiasts! Registration for the 2019 Speaker Design Competition is now open! Visit midwestaudiofest.com for details and to list your speaker project. We are excited to see all returning participants, and look forward to meeting some new designers this year, as well! Be sure your plans include a visit to the Parts Express Tent Sale for the lowest prices of the year, and the Audio Swap Meet where you can buy and trade with other audio fans. We hope to see you this summer! Vivian and Jill
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Stratified ports...

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  • Stratified ports...

    These were demonstrated at MWAF last year, and audioxpress has done an article:
    https://www.audioxpress.com/article/...-quest-engines

    Interesting tech, but applicable?

    Later,
    Wolf
    "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
    "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
    "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
    "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

    *InDIYana event website*

    Photobucket pages:
    http://photobucket.com/Wolf-Speakers_and_more

    My blog/writeups/thoughts here at PE:
    http://techtalk.parts-express.com/blog.php?u=4102

  • #2
    I would like to see more tests/comparisons to ported boxes. Also I am surprised no one has done a see through port design. It would be easy enough if you used 2 ports as long as they weren't too long. Obviously it wouldn't be the same as the "stratified" ports but it would look neat.

    Comment


    • #3
      I've actually thought about it more than once. Mine would have been a cross-drilled port, but the same goal would be accomplished.
      Later,
      Wolf
      "Wolf, you shall now be known as "King of the Zip ties." -Pete00t
      "Wolf and speakers equivalent to Picasso and 'Blue'" -dantheman
      "He is a true ambassador for this forum and speaker DIY in general." -Ed Froste
      "We're all in this together, so keep your stick on the ice!" - Red Green aka Steve Smith

      *InDIYana event website*

      Photobucket pages:
      http://photobucket.com/Wolf-Speakers_and_more

      My blog/writeups/thoughts here at PE:
      http://techtalk.parts-express.com/blog.php?u=4102

      Comment


      • #4
        Those impedance graphs look strange. Not sure how you can claim the tuning is the same based on the impedance graphs. A near filed of the woofer might give more insight
        John H

        Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

        Comment


        • #5
          What looks odd about the impedance? Measured impedance is a good method of verifying cabinet tuning.
          "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
          exactly a Fc 3K for both drivers, anybody can do it." -Xmax

          Comment


          • #6
            The impedance slopes are different above the box tuning. The woofer near field dip is more accurate indicator of the box tuning.
            John H

            Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

            Comment


            • #7
              Oops my bad I just looks at this again on a monitor I was reading the phase...
              John H

              Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

              Comment


              • #8
                Originally posted by jhollander View Post
                The impedance slopes are different above the box tuning. The woofer near field dip is more accurate indicator of the box tuning.
                Nope - while it's where the output of the woofer is at a minimum, the output of the vent is at a maximum, which can influence the measurement. People tend to forget the last part. I've seen several cases of where the measured "Fb" by this approach can vary depending on how close or far the mike is from the vent when placed in front of the woofer.
                Brian Steele
                www.diysubwoofers.org

                Comment


                • #9
                  Originally posted by Brian Steele View Post

                  Nope - while it's where the output of the woofer is at a minimum, the output of the vent is at a maximum, which can influence the measurement. People tend to forget the last part. I've seen several cases of where the measured "Fb" by this approach can vary depending on how close or far the mike is from the vent when placed in front of the woofer.
                  Brian, I said, woofer near field dip is more accurate than impedance dip, here's a picture. What are you saying, that the dip must match the port maximum? Certainly that is not true for an extended shelf alignment.

                  John H

                  Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                  Comment


                  • #10
                    Originally posted by jhollander View Post

                    Brian, I said, woofer near field dip is more accurate than impedance dip, here's a picture. What are you saying, that the dip must match the port maximum? Certainly that is not true for an extended shelf alignment.
                    I'm saying that the **measurement** of that near-field dip may be influenced by the output for the vent, making it an inaccurate way to determine Fb. The key word there is that you're measuring the woofer at a point where its output is at a minimum, and therefore more subject to error. In your somewhat extreme example, the contribution from the vent is still 20dB above the contribution from the woofer at the dip. If that vent is close to the woofer, the measurement will be impacted by the output from the vent.

                    The impedance measurement is subject to no such error.


                    Brian Steele
                    www.diysubwoofers.org

                    Comment


                    • #11
                      You should be measuring at 1 cm from the cone. I've not seen the port SPL "shift" the the woofer minimum SPL, I'd like to see that if you have some data.

                      While I use and like the impedance measurement, port tuning is the point of minimum woofer cone movement. What's a better measurement of minimum cone movement?
                      John H

                      Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                      Comment


                      • #12
                        There were a few mentions on the DIYAudio Subwoofers forum about the issue, and one particularly clear example of the effect ("Fb" changed depending on which part of the cone the mic was held over).
                        I really should have kept the links handy, as this issue comes up from time to time.

                        If you want to use the minimum cone movement, then visual observation may be better - like place some styrotex beans on the cone and determine at what frequency they stop bouncing around, for example. Or place a white dot on the cone and observe at what frequency it stops moving.

                        Brian Steele
                        www.diysubwoofers.org

                        Comment


                        • #13
                          Patent worthy as a design patent, but not as a utility patent. There's plenty of prior art showing the use of multiple ports of various lengths and orientations, with the net result always being that the total is equal to the sum of the parts. You could get the same results with a pair of standard style flared ports placed end to end with a gap between the two entrance flares.
                          www.billfitzmaurice.com
                          www.billfitzmaurice.info/forum

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                          • #14
                            I'm still struggling with The stunning visual aesthetic of see-through ports. Really?
                            Francis

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                            • #15
                              Measurement of near field port, near field woofer, or impedance are all viable methods of making comparisons of tuning. This example (real measurements) has the port on the rear, but you should still be able to determine the tuning using a near field measurement when the port is on the front...If you have overdamped your speaker however, you may find all of these methods a bit more difficult.

                              Now you may say "but the valley in the impedance is a few Hz higher than the acoustic measurement". Sure, that's fine for the purpose of comparison...to ensure two systems are tuned the same, all that matters is that the shape of the curves match. Just the same, when verifying tuning of a cabinet, you would compare the impedance sweep to your simulated cabinet impedance. Methods of using rice etc are only for people who can't build a simple jig, or don't own a mic. For this purpose, any mic can be used, calibrated omnidirectional condenser mic is not required for this purpose.

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                              "I just use off the shelf textbook filters designed for a resistor of 8 ohms with
                              exactly a Fc 3K for both drivers, anybody can do it." -Xmax

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