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Testing LD25X with Waveguides

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  • Testing LD25X with Waveguides

    Jeff B. sent me one of the LD25X tweeters he had so I could test them with the waveguides I had. I went through about 15 different ones that I had on hand. The one that seamed to do the best was my letter H guide elliptical 8x5x2 5/16" with a 40mm throat sitting on top of the existing face plate of the LD25X . Only problem with it was the big dip around 12KHz.

    All measurements are taken on axis, 30 and 45 degrees. Tweeter sitting on a 5" thick 2'x4' rigid fiberglass panel 18" off the floor. Tweeter facing up with mic about 30" above.

    This is the LD25X on a flat rigid fiberglass baffle. Looks like I forgot to pull the gating back on the 30 degree. oops!


    WG H 8x5x2 5/16" 40mm throat sitting on existing tweeter face plate.


    This is the flat baffle vs H guide on axis.


    30 degrees


    45 degrees


    After some experimenting with felt I found if I put small strips on the top and bottom of the guide just inside were it would transition on to the baffle it would take most of the dip out. It pretty much messed up the rest of the response though.
    I made up a few guides that fit the tweeter similar to the way the original face plate mounted on it. I incorporated the shape of the H guide with a few shapes from some of the other guides that seemed to do better on the top end. I also made the eliptical guides more round in hopes of eliminating reflections off the top and bottom of the guide. Seemed to work somewhat.

    WG L 6 x 4 1/2 x 1 1/2 throat 30mm.


    WG U 8 x 5 x 2 3/8 throat 31mm


    WG V 6 x 6 x 2 1/8 throuat 31mm


    WG W 6 1/2 x 5 1/2 x 2 5/16 throat 31mm


    WG X 8 x 6 x 2 1/8 throat 31mm


    This is on axis of the flat baffle -Red, H guide- Green and X guide- Blue. Man if I could just melt the two together.


    I may try an 8" round next with less angle at the throat. maybe that will get rid of the dip on axis.

    Dave
    http://www.pellegreneacoustics.com/

    Trench Seam Method for MDF
    https://picasaweb.google.com/101632266659473725850

  • #2
    Re: Testing LD25X with Waveguides

    Looks like a ton of work Dave.

    Thanks for all your measurements.

    Mark

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    • #3
      Re: Testing LD25X with Waveguides

      Lots of promise...

      Should get a nice low crossover point in the 1000Hz range.
      Dave

      If you can read this, thank a teacher.
      If you are reading it in English thank a Veteran
      .

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      • #4
        Re: Testing LD25X with Waveguides

        After i get it and pull a mold off of it, I can send you a real EOS waveguide if you'd like to test it.

        But it looks like this guy could use a phase plug on these waveguides.

        Comment


        • #5
          Re: Testing LD25X with Waveguides

          Originally posted by winslow View Post
          After i get it and pull a mold off of it, I can send you a real EOS waveguide if you'd like to test it
          The Harman elliptical guide? or just an Elliptical OS guide? I remember Geddes pointing out that "EOS" is a bit misleading because there is no actual EOS geometry... there's ellipsoidal which he uses with elliptical guides and OS which he uses on his conical guides, and is also used in the SEOS guides.

          Anyways the 'U' Guide seemed better than the H guide but i
          might have just compared them wrong???

          Dave, do you mind adding 60deg / 75deg measurements on the superior guide?

          Thanks for this BTW.
          :blues: Flat frequency response, a smooth sound power response free of resonance, careful driver-integration, and high dynamic range both upward and downward :blues:

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          • #6
            Re: Testing LD25X with Waveguides

            To bad about the wonkyness around 12khz. Looks like the <10khz results are way better than the flush mounted results. However, I'd agree it could use a phase plug or something. Not totally happy in a waveguide.

            I thought I'd have a pair for testing by now. Dave (Planet 10) and I haven't been able to connect with our busy schedules. I planned on testing in the Dayton 8". Any chance you have one you could hack up and test with?
            https://www.youtube.com/channel/UCm2...oSKdB448TTVEnQ

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            • #7
              Re: Testing LD25X with Waveguides

              I did try hanging a small piece of dowel rod in front of the tweeter hanging off a piece of wire laying over the guide. It did change the top end but I couldn't get good results with it.

              I can do 60 and 75 degrees. I can also do some verticals as well. I've just been focused on getting rid of the dip.

              I made up a pattern this morning for a round 8" guide. I plan on trying a shallow and deep guide to see how this might effect the top end. Most attempts seem to effect the bottom end more.

              Dave
              http://www.pellegreneacoustics.com/

              Trench Seam Method for MDF
              https://picasaweb.google.com/101632266659473725850

              Comment


              • #8
                Re: Testing LD25X with Waveguides

                Originally posted by davepellegrene View Post
                I can do 60 and 75 degrees. I can also do some verticals as well. I've just been focused on getting rid of the dip.
                Seems like a waste of time TBQH.. I'd be more focused on that little pinch at 30 deg near 2.8khz... i wonder what's causing it.
                :blues: Flat frequency response, a smooth sound power response free of resonance, careful driver-integration, and high dynamic range both upward and downward :blues:

                Comment


                • #9
                  Re: Testing LD25X with Waveguides

                  Originally posted by GranteedEV View Post
                  Seems like a waste of time TBQH.. I'd be more focused on that little pinch at 30 deg near 2.8khz... i wonder what's causing it.
                  It doesn't appear to be in the L guide. Unless it just moved up to 7KHz. L is smaller and shallower then the others.
                  http://www.pellegreneacoustics.com/

                  Trench Seam Method for MDF
                  https://picasaweb.google.com/101632266659473725850

                  Comment


                  • #10
                    Re: Testing LD25X with Waveguides

                    Originally posted by davepellegrene View Post
                    It doesn't appear to be in the L guide. Unless it just moved up to 7KHz. L is smaller and shallower then the others.
                    Do you think increasing the radius of the rounded edge, top and bottom, might help?
                    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
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                    • #11
                      Re: Testing LD25X with Waveguides

                      Do you think increasing the radius o f the rounded edge, top and bottom, might help?
                      I'm assuming you are talking about the baffle edge? I am using a 3/4" round over on the pattern but it does leave a sharper edge on the guide. I think whats going on is when I heat the plexiglass I have it sandwiched between two pieces of 3/4". So I think the heat is being blocked at a clean line creating a slight edge. I'll look into cutting the top hold down piece a little larger to see if that helps. I was looking into that this morning. I'm thinking I may be able to heat the edge up on the finished guides and soften it. If so i can get a direct comparison.
                      Dave
                      http://www.pellegreneacoustics.com/

                      Trench Seam Method for MDF
                      https://picasaweb.google.com/101632266659473725850

                      Comment


                      • #12
                        Re: Testing LD25X with Waveguides

                        I am talking about the edge were the guide meets the baffle.
                        http://www.pellegreneacoustics.com/

                        Trench Seam Method for MDF
                        https://picasaweb.google.com/101632266659473725850

                        Comment


                        • #13
                          Re: Testing LD25X with Waveguides

                          The JBL/Harman one. I ordered one from JBL Pro Parts last week. It's my plan B for the car if I can't get the micro-sized Unity-style horns working in the doors.

                          Originally posted by GranteedEV View Post
                          The Harman elliptical guide? or just an Elliptical OS guide? I remember Geddes pointing out that "EOS" is a bit misleading because there is no actual EOS geometry... there's ellipsoidal which he uses with elliptical guides and OS which he uses on his conical guides, and is also used in the SEOS guides.

                          .

                          Comment


                          • #14
                            Re: Testing LD25X with Waveguides

                            Originally posted by winslow View Post
                            The JBL/Harman one. I ordered one from JBL Pro Parts last week. It's my plan B for the car if I can't get the micro-sized Unity-style horns working in the doors.
                            I'd love to see how an LD25X performs in one of those. What side did you order? the ~4" one in the LSR6332?

                            What size is the JBL dome?
                            Last edited by GranteedEV; 02-29-2012, 05:14 PM.
                            :blues: Flat frequency response, a smooth sound power response free of resonance, careful driver-integration, and high dynamic range both upward and downward :blues:

                            Comment


                            • #15
                              Re: Testing LD25X with Waveguides

                              Originally posted by davepellegrene View Post
                              I did try hanging a small piece of dowel rod in front of the tweeter hanging off a piece of wire laying over the guide. It did change the top end but I couldn't get good results with it.

                              I can do 60 and 75 degrees. I can also do some verticals as well. I've just been focused on getting rid of the dip.

                              I made up a pattern this morning for a round 8" guide. I plan on trying a shallow and deep guide to see how this might effect the top end. Most attempts seem to effect the bottom end more.

                              Dave
                              Hey Dave, that high-Q narrow band notch at 12khz that exists on-axis, but disappears at 30 degrees off axis should be completely inconsequential to anyone other than someone looking at lines on a graph. This kind of narrow-band notch at a narrow angle should not be audible. However, it does appear to be caused by a reflection in the throat of the waveguide based on the short wavelength of the frequency affected.

                              Thanks for the post.

                              Jeff
                              Click here for Jeff Bagby's Loudspeaker Design Software

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