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UM8-22 WinISD port calculations not even close

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  • UM8-22 WinISD port calculations not even close

    I'm trying to model a UM8-22 in a ported enclosure. PE has the recommended specs as a 0.75 cubic ft box tuned to 30 Hz, with a 1" x 10" x 30" port. I am just messing around with the settings and trying to duplicate the 30" port and I'm not even coming close. Can someone point me in the right direction? I'm trying to duplicate PE's design in WinISD before i start modifying the design to something a little more custom. I am thinking about building a dual triangle port that looks like HSU Research's VTF-15. S

  • #2
    Your entered Vent Length appears to be 0.09". Unless I'm reading that wrong.
    Francis

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    • #3
      I wouldn't put the UM22 in a box that size. If going ported it should be at least 1 cu ft, otherwise the port has to be way too long to get useful tuning. At 1 cu ft you could use an 8 square inch by 20 inch long port. A 1x10 port is not a good idea either, very narrow ports have wall friction problems. That said, the UM8 isn't well suited to a ported box, Qes is too high. It models best in 1.5 cu ft sealed.
      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        And yeah, like Bill says, skinny ports are non-optimum. Round is best for a reason.
        Francis

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        • #5
          WinISD likes 2-1/2cf tuned to the low 20s. I think 0.75cf tuned "for an F3 of 30" (in PE's suggestions - NOT an Fb of 30) is too small.
          How about a compromise??

          Take a look at 1.5cf tuned in the mid 20s. (F3 low 20s. A 18" long 3" "Precision Port" MIGHT to the trick.)

          Did you know you can "click" the "Box" tab, then click inside the vented box icon and (basically) slowly drag the curve around to get any kind of F3/rolloff shape you like?
          You COULD build that same size (vented) box, and if you don't like it (or it "booms" in your room placement) - you can plug the vent for an F3 near 40 (which should be pretty good w/just music content).

          (Your post title is pretty misleading - BTW. Who's to say that "Bassbox Pro" is right? Not only that, but I think you misread the ported box suggestion.)

          Comment


          • #6
            Thanks for the suggestions. I'm going dig around WinISD a little more. I'm agreeable to a bigger box. And like a said, I'm not a fan of the slotted port, as I'm looking to make 2 triangle ports. see attached

            Comment


            • #7
              Originally posted by fpitas View Post
              Your entered Vent Length appears to be 0.09". Unless I'm reading that wrong.
              you can't change the port length. You enter tuning frequency and diameter and the software kicks out length.

              Comment


              • #8
                Originally posted by nickg2027 View Post
                TAnd like a said, I'm not a fan of the slotted port, as I'm looking to make 2 triangle ports. see attached
                Just say no to triangle ports. They're the worst of the bunch. More lossy than the others.
                Brian Steele
                www.diysubwoofers.org

                Comment


                • #9
                  Originally posted by Chris Roemer View Post
                  WinISD likes 2-1/2cf tuned to the low 20s. I think 0.75cf tuned "for an F3 of 30" (in PE's suggestions - NOT an Fb of 30) is too small.
                  How about a compromise??

                  Take a look at 1.5cf tuned in the mid 20s. (F3 low 20s. A 18" long 3" "Precision Port" MIGHT to the trick.)

                  Did you know you can "click" the "Box" tab, then click inside the vented box icon and (basically) slowly drag the curve around to get any kind of F3/rolloff shape you like?
                  You COULD build that same size (vented) box, and if you don't like it (or it "booms" in your room placement) - you can plug the vent for an F3 near 40 (which should be pretty good w/just music content).

                  (Your post title is pretty misleading - BTW. Who's to say that "Bassbox Pro" is right? Not only that, but I think you misread the ported box suggestion.)
                  Ok. Here is why I'm stuck. I'm trying to model this box and the port length is now showing a negative value. What I am doing wrong?!?!

                  I did not know about the box dragging tool, pretty neat.
                  Attached Files

                  Comment


                  • #10
                    Originally posted by Brian Steele View Post

                    Just say no to triangle ports. They're the worst of the bunch. More lossy than the others.
                    no triangle ports? Dang, I think they look super cool. Round it is then.

                    Comment


                    • #11
                      I haven't experienced any problems with triangle ports. They also have the advantage of doing double duty as side braces. I'd use four, though, not two. That way air pressure distribution in the cab is more even, reducing the possibility of cone rocking.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

                      Comment


                      • #12
                        Originally posted by billfitzmaurice View Post
                        I haven't experienced any problems with triangle ports. They also have the advantage of doing double duty as side braces. I'd use four, though, not two. That way air pressure distribution in the cab is more even, reducing the possibility of cone rocking.
                        That sounds and looks really cool. But I still have the problem of WinISD giving me anything usable for port length/width/diameter. I really trust you all's opinion as I'm new to all of this. But I'd still like to get WinISD working properly so i can tinker with specs.

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                        • #13
                          Yeah that's messed up. Box tuning is what it is, regardless of the driver. Try reinstalling WinISD.

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                          • #14
                            Can you post a screenshot of the T/S parameters entered?
                            ----------------------------------------------------------------------------------

                            Comment


                            • #15
                              Yeah, something's hosed up there.
                              The port resonance is tied to it's length, and a 1/10" long port won't resonate at 17kHz (unless your "Environment" - under "Plot", is screwed up).
                              Try a reload (I use 0.50a7 - the old "Pro" (beta) version).

                              Your PLOT looks exactly like mine (and your box vol. and tuning are good), but your port length should be like 33" or so.

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