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  • #16
    Originally posted by Wolf View Post

    Bingo! Man- I really wasn't being snarky....

    Later,
    Wolf
    ​It's times like this that I really wish I had kept all my original issues of Speaker Builder Magazine. Port tube turbulence and ways to minimize it were discussed way before the advent of the internet.

    Comment


    • #17
      Originally posted by fdieck View Post
      Straws in the port is actually aperiodic damping I believe.
      ​Nope.
      But if you tightly stuffed a bass reflex port with a wad of fiberglas or polyester batting, then you could probably call that aperiodic.
      The Dynaudio Variovent was pretty much just that.

      Comment


      • #18
        Originally posted by billiam View Post
        It always amazes me how pissy people get when they feel like a question is posted that isn't worth their time. Hey, you know what? IF YOU FEEL THAT WAY, DON'T RESPOND TO THE DAMN POST. Enjoy your effing lives. Parts Express just lost a customer.
        Bill, you definitely mistook people trying to help you as something else. Every response was legit advice to what you asked. Engage and you will get
        ​good advice. BTW I enjoy my F'n life.

        Comment


        • #19
          Am I missing something here? More than one person has mentioned the diameter affecting port resonance. If you exclude end correction (assuming length is significantly larger than diameter), then the only variable in calculating the resonance of an open (or closed) column of air is the length. Assuming you keep the same net box volume, box tuning, and total port cross sectional area, increasing the number of ports (and decreasing their diameter appropriately) will result in the same length for each port, and result in the same port resonance frequency.

          Port resonance (in its most basic form) can be calculated as: f=v/(2L) , where f = first port resonance frequency, v = speed of sound, and L = length of port. There is no variable for the diameter of the pipe. WinISD and Unibox both confirm in simulations that a single 2" port of a given length, and 4 x 1" ports of the same length, in the same size box, yield the same tuning, and the same 1st port resonance.

          Comment


          • #20
            Check the box in Unibox that says 'Include effect of port resonance', just below the 'Port 1. resonance' value. This will be what I am referring to, not the actual tuning of the box or the Fb..

            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


            • #21
              Originally posted by Wolf View Post
              Check the box in Unibox that says 'Include effect of port resonance', just below the 'Port 1. resonance' value. This will be what I am referring to, not the actual tuning of the box or the Fb..

              Later,
              Wolf
              Yes, it IS checked. It typically causes a hyperbolic looking response. HornResp will typically show the same hyberbolic looking response when . There is even a value in the spreadsheet in Unibox where it lists the first port resonance, and again, that number is determined by port length, not diameter.

              Comment


              • #22
                I guess that may have been an assumption I made, as when I decreased the diameter and used multiples, the effect was diminished. Thing is, the same cross-sectional area, and a single or multiple smaller, were very different in terms of the resonance shown. If the hyperbolic response you describe then has a peak and then flattens back out, or has multiple dip/peak combinations, this is where I change things so this does not happen. Since length did not change, I thought it was a function of diameter.

                Thanks,
                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


                • #23
                  I recall seeing tests that showed smaller diameter ports have less midrange leakage. Whether having two (for example) smaller ports vs. one larger port improves the overall situation, I don't know.
                  Francis

                  Comment


                  • #24
                    Originally posted by Wolf View Post
                    I guess that may have been an assumption I made, as when I decreased the diameter and used multiples, the effect was diminished. Thing is, the same cross-sectional area, and a single or multiple smaller, were very different in terms of the resonance shown. If the hyperbolic response you describe then has a peak and then flattens back out, or has multiple dip/peak combinations, this is where I change things so this does not happen. Since length did not change, I thought it was a function of diameter.

                    Thanks,
                    Wolf
                    Hmm, when I was playing with it in Unibox last night, I saw no change to the FR plots when changing from a single 10-cm port, to four 5-cm ports, to sixteen 2.5-cm ports in an example sim.

                    Comment


                    • #25
                      Now you have me curious...
                      I'll see if I can't find my older Canvas models to show.

                      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


                      • #26
                        Originally posted by Wolf View Post
                        Now you have me curious...
                        I'll see if I can't find my older Canvas models to show.

                        Later,
                        Wolf
                        I'm pretty sure I double-checked everything last night, but I will pull it it back up and triple-check it again tonight if I get a chance.

                        Comment


                        • #27
                          Originally posted by Wolf View Post
                          Shove some straws in your round ports!
                          Later,
                          Wolf
                          Maybe next time tell him to shove the straws up his nose!

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