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Can someone model a sub for me?

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  • Can someone model a sub for me?

    Just curious what numbers some other's get with this driver, in a .75 CuFt. Box

    Vas .54 Cuft.
    Qts .6
    Fs 35Hz

    With a 3" port, not sure ideal length

  • #2
    Re: Can someone model a sub for me?

    Oh, about low 30s w/a 3"id x 2 foot long port (Fb also in the low 30s).
    I'd probably double the box size though. An Fb near 25Hz (3"d x 18") yields an F3 in the low 20s.

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    • #3
      Re: Can someone model a sub for me?

      I'd seal that port up and call it a day. F3 of 38Hz with a nice, shallow 12dB/octave rolloff. On the ground against a wall will give you flat in room response into the 20s in most rooms. And you won't have to wrestle a 24" long port into your box.

      Dan
      _____________________________
      Tall Boys
      NRNP Computer Sub
      The Boxers
      The Hurricanes
      The Baronettes
      Conneccentric
      UX3

      Comment


      • #4
        Re: Can someone model a sub for me?

        Originally posted by Chris Roemer View Post
        Oh, about low 30s w/a 3"id x 2 foot long port (Fb also in the low 30s).
        I'd probably double the box size though. An Fb near 25Hz (3"d x 18") yields an F3 in the low 20s.
        Haha thanks chris. Only 24 inches..!

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        • #5
          Re: Can someone model a sub for me?

          Originally posted by DanP View Post
          I'd seal that port up and call it a day. F3 of 38Hz with a nice, shallow 12dB/octave rolloff. On the ground against a wall will give you flat in room response into the 20s in most rooms. And you won't have to wrestle a 24" long port into your box.

          Dan
          Interesting also. And thanks.

          Comment


          • #6
            Re: Can someone model a sub for me?

            Originally posted by DanP View Post
            I'd seal that port up and call it a day. F3 of 38Hz with a nice, shallow 12dB/octave rolloff. On the ground against a wall will give you flat in room response into the 20s in most rooms. And you won't have to wrestle a 24" long port into your box.

            Dan
            Hey dan was re-reading this. I tried modeling it going closed box, and the lowest F3 I could get, was a bit over 41hz.


            That was with a Qtc of .79 and Volume of .74 Cu.Ft.

            Comment


            • #7
              Re: Can someone model a sub for me?

              Originally posted by kevintomb View Post
              Hey dan was re-reading this. I tried modeling it going closed box, and the lowest F3 I could get, was a bit over 41hz.


              That was with a Qtc of .79 and Volume of .74 Cu.Ft.
              Probably just the difference in our modelling algorithms. I use the theoretical calculations because I can do them on a calculator: Vb = Vas/((Qtc/Qts)^2-1) and F3 = Fs*C*Qtc/Qts where C is a proportional factor based on Qtc that I have memorized for a few different Qtc values.

              What my calculations are missing that yours probably include are a lumped loss value Ql, which will bring the simulation closer to reality, but I promise you won't miss the 3Hz difference. If you're using a modeling program like WinISD, this Ql value is probably included and will be more accurate than the theoretical performance I gave.

              Dan
              _____________________________
              Tall Boys
              NRNP Computer Sub
              The Boxers
              The Hurricanes
              The Baronettes
              Conneccentric
              UX3

              Comment


              • #8
                Re: Can someone model a sub for me?

                Originally posted by DanP View Post
                Probably just the difference in our modelling algorithms. I use the theoretical calculations because I can do them on a calculator: Vb = Vas/((Qtc/Qts)^2-1) and F3 = Fs*C*Qtc/Qts where C is a proportional factor based on Qtc that I have memorized for a few different Qtc values.

                What my calculations are missing that yours probably include are a lumped loss value Ql, which will bring the simulation closer to reality, but I promise you won't miss the 3Hz difference. If you're using a modeling program like WinISD, this Ql value is probably included and will be more accurate than the theoretical performance I gave.

                Dan
                Hah its cool, wasn't calling you out on it, but just interesting how slightly different numbers are created.

                I really get into the modeling part. I am too obsessive to create even half of the ideas I get or keep coming up with.
                I think I have modeled over 30 subs, and there is no ideal sub for everything..LOL

                Comment


                • #9
                  Re: Can someone model a sub for me?

                  and there is no ideal sub for everything
                  It is a continuum - an interplay between the characteristics of a driver and the air around it.
                  "Not a Speaker Designer - Not even on the Internet"
                  “Pride is your greatest enemy, humility is your greatest friend.”
                  "If the freedom of speech is taken away, then dumb and silent we may be led, like sheep to the slaughter."

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                  • #10
                    Re: Can someone model a sub for me?

                    First, the pressure hull should be shaped like a whale...:D

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