Announcement

Collapse
No announcement yet.

Driver Size, Off-Axis

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Driver Size, Off-Axis

    An apostrophe with an "s" does not mean plural.

    Speaker's IS NOT PLURAL.

  • #2
    Re: Driver Size, Off-Axis

    It's hard to put an exact number on it, it depends on cone diameter, cone profile, etc, but it's not important to be ultra precise and there's a ROF which states that beaming will start to occur at roughly 13550 / cone diameter (inches).

    PCD will visually show you the estimated off axis behavior.
    Don't even try
    to sort out the lies
    it's worse to try to understand.

    Comment


    • #3
      Re: Driver Size, Off-Axis

      PCD requires Office.

      13550/6.5 = 2,084

      Correct?

      I guess other factors play a big role, because this guy is -5dB @ 1,500........
      http://www.parts-express.com/pe/psho...4-1146&scqty=2
      An apostrophe with an "s" does not mean plural.

      Speaker's IS NOT PLURAL.

      Comment


      • #4
        Re: Driver Size, Off-Axis

        Originally posted by icor1031 View Post
        How do I calculate how a driver should respond off-axis?
        Use Google books to get to Sound System Engineering by Don Davis, Eugene Patronis
        page 264 has the formulas
        "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."

        Comment


        • #5
          Re: Driver Size, Off-Axis

          Thanks, impressive.


          Also,
          This book uses -6dB.
          Isn't that way too low? Shouldn't it be -3 at most?

          Originally posted by Sydney View Post
          Use Google books to get to Sound System Engineering by Don Davis, Eugene Patronis
          page 264 has the formulas
          An apostrophe with an "s" does not mean plural.

          Speaker's IS NOT PLURAL.

          Comment


          • #6
            Re: Driver Size, Off-Axis

            Originally posted by icor1031 View Post
            Thanks, impressive.


            Also,
            This book uses -6dB.
            Isn't that way too low? Shouldn't it be -3 at most?
            I'm not sure how to answer that as I don't know what your goal is...
            "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."

            Comment


            • #7
              An apostrophe with an "s" does not mean plural.

              Speaker's IS NOT PLURAL.

              Comment


              • #8
                Re: Driver Size, Off-Axis

                Yeah, best to listen to Sydney, apparently I'm not thinking clearly this evening and I gave you the wrong ROF. Since getting to page 264 on my slow dial up isn't going to happen in this lifetime and I can't even download the driver spec sheet at the moment I did a quick search for beaming start frequency.

                On this forum they frequently use the formula 11500 / driver diameter (inches).
                In other places on this forum and around the web it's stated as 1/2 (or 1) wavelength. (The formula I gave describes 1 wavelength.)

                But I suspect (and PCD seems to back this up) that the on axis response starts to diverge from off axis at around 500 hz or so, which is ~1/4 wavelength of a 6.5.
                Don't even try
                to sort out the lies
                it's worse to try to understand.

                Comment


                • #9
                  Re: Driver Size, Off-Axis

                  As mentioned ( in post 2 ) it is difficult to come up with an exact figure, because the theoretical calculations are based upon a flat piston, which a speaker cone isn't. A particular cone may be designed to affect dispersion.

                  Additional discussion:
                  page 13 - 16 of Loudspeaker and Headphone Book by John Borwick

                  page 64 of Electroacostical Reference Data by John Eargle

                  Note what happens when Ka > 1
                  "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."

                  Comment


                  • #10
                    Re: Driver Size, Off-Axis

                    Here's a visual answer to your question...

                    Click image for larger version

Name:	dispersion vs wavelength.jpg
Views:	1
Size:	89.1 KB
ID:	1139864

                    Looking at the plots, clearly when the driver is asked to reproduce wavelengths significantly longer than it's diameter, it does so very well... with wide dispersion.

                    The dispersion gets much worse as the wavelengths approach the diameter of the driver.
                    ~Marty

                    Baby Eidolons
                    Sapphos
                    Cables (Post #54)
                    Other speakers (Post #21)
                    Design Thoughts (Posts: 6,10,13,33,35)
                    Boundary Augmentation
                    Dispersion/Interference

                    Comment


                    • #11
                      Re: Driver Size, Off-Axis

                      Anyway, PCD shows response is -3 db at 80 degrees at approximately 1500 hz for an actual measured cone diameter of 5.5 inches (which should be ~accurate for a 6.5 inch driver.

                      (I should know this stuff better by now, I just had a very similar conversation a couple of months ago.)
                      Don't even try
                      to sort out the lies
                      it's worse to try to understand.

                      Comment


                      • #12
                        Re: Driver Size, Off-Axis

                        That is a lovely graph... It also makes me want to redo my project, but I don't want to build a 4-way.. lol..

                        Originally posted by ReissM View Post
                        Here's a visual answer to your question...

                        [ATTACH]22161[/ATTACH]

                        Looking at the plots, clearly when the driver is asked to reproduce wavelengths significantly longer than it's diameter, it does so very well... with wide dispersion.

                        The dispersion gets much worse as the wavelengths approach the diameter of the driver.
                        An apostrophe with an "s" does not mean plural.

                        Speaker's IS NOT PLURAL.

                        Comment


                        • #13
                          Re: Driver Size, Off-Axis

                          Thanks, mate.

                          Originally posted by diy speaker guy View Post
                          Anyway, PCD shows response is -3 db at 80 degrees at approximately 1500 hz for an actual measured cone diameter of 5.5 inches (which should be ~accurate for a 6.5 inch driver.

                          (I should know this stuff better by now, I just had a very similar conversation a couple of months ago.)
                          An apostrophe with an "s" does not mean plural.

                          Speaker's IS NOT PLURAL.

                          Comment


                          • #14
                            Re: Driver Size, Off-Axis

                            Here's what PCD says. For a generic 6.5 inch driver from my files (actual cone diameter 5.5 inches) at 0 and 80 degrees.

                            Don't even try
                            to sort out the lies
                            it's worse to try to understand.

                            Comment


                            • #15
                              Re: Driver Size, Off-Axis

                              Check out the directivity graphs on that SEOS-12 and a B&C DE250, they're pretty darn good. I think I might build 7 speakers for HT with them.

                              रेतुर्न तो थे स्रोत
                              return to the source
                              leviathan system thread
                              deadhorse thread
                              shockwave build thread

                              instagram :: greywarden_13

                              in war, victory . . . in peace, vigilance . . . in death, sacrifice.

                              Comment

                              Working...
                              X