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Design topology for a "classic" 3-way

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  • Design topology for a "classic" 3-way

    Hi all,

    in a earlier post:

    http://techtalk.parts-express.com/fo...ct-a-10-woofer

    I have asked for your advice on the ch oice of woofer for my next project. This post is more on the design process. Please look at the attached pictures. My plan is to design the system "from the top" starting with the upper smaller mid/tweeter box and, basically, design a two-way crossed at abt 3000 Hz.

    The measurements on that "semi-system" will be a good guide on how to proceed with the woofer-part, housed in the lower box.

    I plan to aim for 2nd order wo/mid and 2nd/3rd mid/tweeter.

    Any thoughts on this?

    Regards//lasse
    Stockholm, Sweden

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    Attached Files
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

  • #2
    Post disappeared??

    Regards//lasse
    Perry Mason talking to his dentist:

    "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

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    • #3
      Originally posted by lasse View Post
      Post disappeared??

      Regards//lasse
      2nd order mid and woofer but I’d wait to decide on the slopes up high and let the drivers tell you what they want
      R = h/(2*pi*m*c) and don't you forget it! || Periodic Table as redrawn by Marshall Freerks and Ignatius Schumacher || King Crimson Radio
      Byzantium Project & Build Thread || MiniByzy Build Thread || 3 x Peerless 850439 HDS 3-way || 8" 2-way - RS28A/B&C8BG51

      95% of Climate Models Agree: The Observations Must be Wrong
      "Gravitational systems are the ashes of prior electrical systems.". - Hannes Alfven, Nobel Laureate, Plasma physicist.

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      • #4
        Pete's comment is spot on. My old 3-way was classic is in the same sense, a 25W woofer in a PR box with a small 2-way on top. XO was W/M 300Hz LR2 and M/T 3000Hz LR2 as well. In most cases the tweeter will dictate the lower limit of your filter as long as the mid is good to that point. That old 3-way design is up at my site, my favorite before I moved to my current dipoles.

        25W8565-01 / 12M4631 / OW1

        One detail in the crossover allowed the mid to match well that isn't often used now, but is an old classic technique. I used a series RC bypass to extend the midrange top end that allowed for a better integration with the tweeter. One other detail is that the mid is slightly offset forward to roughly align the centers, making the M/T crossover easier, especially being 2nd order.

        dlr
        WinPCD - Windows .NET Passive Crossover Designer

        Dave's Speaker Pages

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        • #5
          Originally posted by Pete Schumacher View Post

          2nd order mid and woofer but I’d wait to decide on the slopes up high and let the drivers tell you what they want
          Hi and thanks for the advice.
          I Will build the mid/tw-box, installera the drivers and measure

          will be back!!

          regards/lasse
          Perry Mason talking to his dentist:

          "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

          Comment


          • #6
            Lasse, I have used that Peerless mid/woofer in a previous project and really liked how it sounded. Have you considered using it open baffle?
            Craig

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            • #7
              Originally posted by PWR RYD View Post
              Lasse, I have used that Peerless mid/woofer in a previous project and really liked how it sounded. Have you considered using it open baffle?
              Hi,
              actually no because I have never used that OB-design up until Today.
              Is there somewhere I can read about the pros/cons and the expected performance?

              regards// lasse
              Perry Mason talking to his dentist:

              "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

              Comment


              • #8
                http://www.musicanddesign.com/A_B_C_Dipole.html
                Craig

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                • #9
                  Hello all,

                  just a picture of "work in progress"

                  The tweeters will be flush mounted but not the mid.

                  Regards//lasse Click image for larger version

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ID:	1388056
                  Perry Mason talking to his dentist:

                  "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                  Comment


                  • #10
                    Have you considered rotating the woofer 90* so that the flat sides of the woofer and tweeter touch each other. This will get you a closer center to center distance and possibly get a little better driver integration.
                    -Bob

                    The PEDS 2.1 mini system
                    My A7 Project - another small desktop speaker
                    The B3 Hybrid Dipole - thread incomplete and outdated

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                    • #11
                      Originally posted by BOBinGA View Post
                      Have you considered rotating the woofer 90* so that the flat sides of the woofer and tweeter touch each other. This will get you a closer center to center distance and possibly get a little better driver integration.
                      Hi,

                      and thanks for the feedback.

                      There are two main reasons for the choice of mid-orientation:
                      The screws should be free from the baffle-mounting arrangement in order to facilitate bolt and wafer on the back of the baffle
                      I wanted to show a curved surface to the tweeter for diffraction control reasons (could be debated upon??)

                      I wanted to surface mount the mid to align the AC´s as well as possible.

                      regards//lasse
                      Perry Mason talking to his dentist:

                      "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                      Comment


                      • #12
                        Originally posted by lasse View Post
                        Hello all,

                        just a picture of "work in progress"

                        The tweeters will be flush mounted but not the mid.

                        Regards//lasse Click image for larger version

Name:	IMG_0009.jpg
Views:	1
Size:	73.8 KB
ID:	1388056
                        That 830991 driver has really nice midrange. I made a few temporary 3-ways with it, stacking boxes like you are here, but didn't finish the speakers. I tend to go overboard sometimes on the x-overs, and the part count was too high.

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                        • #13
                          Originally posted by rpb View Post

                          That 830991 driver has really nice midrange. I made a few temporary 3-ways with it, stacking boxes like you are here, but didn't finish the speakers. I tend to go overboard sometimes on the x-overs, and the part count was too high.
                          Hi,

                          yes part count...

                          my ambition is to keep the count as low as possible. My personal theory is that some of the ”life” in the music dissappear when you add a lot of passive components in the signal path. Perhaps you have to pay in terms of a not-so-perfect flat response. I think that the more important thing is to flatten the impedance in order to make the XO to work properly.

                          just my 2 öres ( that is swedish cents.....)

                          regards// lasse
                          Perry Mason talking to his dentist:

                          "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                          Comment


                          • #14
                            ...and here is a picture of the completed mid/tw units.

                            Regards//lasse


                            Click image for larger version

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                            Perry Mason talking to his dentist:

                            "Do you swear to take the tooth, the whole tooth and nothing but the tooth, so help you God?"

                            Comment


                            • #15
                              Originally posted by lasse View Post

                              Hi,

                              and thanks for the feedback.

                              There are two main reasons for the choice of mid-orientation:
                              The screws should be free from the baffle-mounting arrangement in order to facilitate bolt and wafer on the back of the baffle
                              I wanted to show a curved surface to the tweeter for diffraction control reasons (could be debated upon??)

                              I wanted to surface mount the mid to align the AC´s as well as possible.

                              regards//lasse
                              I understand the mounting issue and I think that the extra distance isn't a big issue. However, the edge being round/flat isn't much of a consideration with regard to diffraction because the edge of a driver such as that doesn't contribute a significant amount. The distances from tweeter to edge are distributed in both cases and the surface is small. What is an issue is the diffraction created by the mid-woofer cone surface. The closer it is, the worse the diffraction due to a larger included angle and the wavelengths affected.

                              If you really want to control some of the diffraction, a single piece of 1/2" high felt maybe only 4-5 inches long placed between the two drivers will work very well. But you don't have a lot of room for that with the raised mounting plate of the mid-woofer.

                              dlr
                              WinPCD - Windows .NET Passive Crossover Designer

                              Dave's Speaker Pages

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