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TangBand 75-1558SE on a Waveguide with Measurements

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  • #76
    Re: TangBand 75-1558SE on a Waveguide with Measurements

    Since we are looking at German speakers here is a documented similar effort.

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    • #77
      Re: TangBand 75-1558SE on a Waveguide with Measurements

      Originally posted by andy19191 View Post
      Since we are looking at German speakers here is a documented similar effort.
      While doing research on the combo guide using the TB75 I came across this link. My first prototype was taken from it. What I had found was the sharp edge between the two guides added quite a bit of diffraction on the tweeter on axis. Spreading the guides apart so each is a full guide took care of the diffraction and also added a couple dbs of boost on the bottom end.



      I'm just finishing up a combo guide with the TB75 and the SS D2604. I plan to do an A/B test against the Audax TW25.

      I'll be posting my results in my thread with the combo guide here.
      http://techtalk.parts-express.com/sh...ombo-Waveguide

      Dave
      http://www.pellegreneacoustics.com/

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

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      • #78
        Re: TangBand 75-1558SE on a Waveguide with Measurements

        Originally posted by davepellegrene View Post
        While doing research on the combo guide using the TB75 I came across this link. My first prototype was taken from it. What I had found was the sharp edge between the two guides added quite a bit of diffraction on the tweeter on axis. Spreading the guides apart so each is a full guide took care of the diffraction and also added a couple dbs of boost on the bottom end.
        That would be an interesting comparison to see. Both K&H and Genelec have opted to keep the sharp edge which suggests the pros and cons may not be clear cut. Perhaps an answer in your thread rather than Brandon's would be tidier.

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        • #79
          Re: TangBand 75-1558SE on a Waveguide with Measurements

          Originally posted by andy19191 View Post
          That would be an interesting comparison to see. Both K&H and Genelec have opted to keep the sharp edge which suggests the pros and cons may not be clear cut. Perhaps an answer in your thread rather than Brandon's would be tidier.
          I think the pros and cons are pretty clear cut. Dave has shown that smoother response results from two distinct guides. It may add a little CTC distance which would be the down side. But improved performance for the tweeter response is the obvious benefit. Genelec and K&H simply made the choice to go with a little extra diffraction ripple and keep the spacing tighter.
          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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          • #80
            Re: TangBand 75-1558SE on a Waveguide with Measurements

            I think the pros and cons are pretty clear cut. Dave has shown that smoother response results from two distinct guides. It may add a little CTC distance which would be the down side. But improved performance for the tweeter response is the obvious benefit. Genelec and K&H simply made the choice to go with a little extra diffraction ripple and keep the spacing tighter.
            Has Dave shown results for the sharp edge case that I have missed?

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            • #81
              Re: TangBand 75-1558SE on a Waveguide with Measurements

              Spreading the guides apart pushed the CTC spacing 3/8" wider then what the spacing would be with the TB75 and XT25TG30 on a flat baffle. With the guides overlapping as in the Genelec and K&H guides the CTC was 4" in my test guide. Spreading them apart made for a 5.5" spacing. I do not believe I posted the results as I was developing these for a client in France at the time. With the crossover point being between 1.6 kHz and 2.0 kHz I didn't think the CTC was as important as a smoother on axis measurement. I should have the measurements on my laptop and could post them if there is interest.

              Dave
              http://www.pellegreneacoustics.com/

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

              Comment


              • #82
                Re: TangBand 75-1558SE on a Waveguide with Measurements

                Originally posted by davepellegrene View Post
                Spreading the guides apart pushed the CTC spacing 3/8" wider then what the spacing would be with the TB75 and XT25TG30 on a flat baffle. With the guides overlapping as in the Genelec and K&H guides the CTC was 4" in my test guide. Spreading them apart made for a 5.5" spacing. I do not believe I posted the results as I was developing these for a client in France at the time. With the crossover point being between 1.6 kHz and 2.0 kHz I didn't think the CTC was as important as a smoother on axis measurement. I should have the measurements on my laptop and could post them if there is interest.
                Was the ripple introduce by the edge largely present in the horizontal off-axis plots? If so, the horizontal directivity would be largely fixable in the crossover although not the vertical.

                The most informative way to study all this in a quantifiable way is probably to perform a set of acoustic wave simulations. A few years ago it was near the top of my to-do list but it has steadily slipped down. The lack of enthusiasm of the local TB distributor for the 3" dome was what started things rolling down hill.

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                • #83
                  Re: TangBand 75-1558SE on a Waveguide with Measurements

                  Originally posted by andy19191 View Post
                  Was the ripple introduce by the edge largely present in the horizontal off-axis plots? If so, the horizontal directivity would be largely fixable in the crossover although not the vertical.

                  The most informative way to study all this in a quantifiable way is probably to perform a set of acoustic wave simulations. A few years ago it was near the top of my to-do list but it has steadily slipped down. The lack of enthusiasm of the local TB distributor for the 3" dome was what started things rolling down hill.
                  It only stands to reason that a sharp edge will introduce more ripple on axis than a smooth transition. And because these types of monitors are usually listened to fairly close to on-axis, getting a smooth response on axis would seem to be more important than worrying about the forward lobe being a couple degrees narrower, IMO.
                  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.

                  Comment


                  • #84
                    Re: TangBand 75-1558SE on a Waveguide with Measurements

                    Originally posted by augerpro View Post
                    I think I have a usable waveguide now. Very simple 3/4" deep, 3/4" chamfer, and 3 13/16" throat. And after a lot of baffle sims and a few prototypes to see just how well the sims' results work with an actual crossover in place, I measured on the final baffle design. My 3 way will move forward now: 8" Peerless HDS woofer (for now), hopefully a Transducer Lab tweeter, and one version with the TB dome mid and another using the BG Neo8. Here is a pic of the mockup of the final baffle, raw response of the TB, and after a LR4 bandpass crossover is in place at 700hz and 2600hz:

                    Not sure if I'll do anything about the higher frequency response peak. I was listening to this (and a few other drivers) unfiltered the other day and it sounds really smooth, the higher frequencies just melt away. No wonder midband distortion is so low.
                    Hi Brandon,

                    sorry to resurrect this thread but I'm curious how you treated the gap created by the faceplate when mounted to a even surface/from behind? Modeling clay?
                    I want to use the mid exactly the same way soon.

                    Thanks
                    Jochen

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                    • #85
                      Re: TangBand 75-1558SE on a Waveguide with Measurements

                      Originally posted by JochenM View Post
                      Hi Brandon,

                      sorry to resurrect this thread but I'm curious how you treated the gap created by the faceplate when mounted to a even surface/from behind? Modeling clay?
                      I want to use the mid exactly the same way soon.

                      Thanks
                      Jochen
                      I used the speaker gasket material from PE, basically 1/8" thick black weather stripping. I think I posted somewhere in this thread about the effect without the foam strip, it is measurable. But just flush with the mouth of the waveguide corrects it just fine.
                      ~Brandon
                      Please donate to my Waveguides for CNC and 3D Printing Project!!
                      Please donate to my Monster Box Construction Methods Project!!
                      Soma Sonus

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                      • #86
                        Re: TangBand 75-1558SE on a Waveguide with Measurements

                        It was indeed on the first page ;)
                        Did you again use that slight 1/8" "ring" that was not routed away and that you've marked in the picture on page 1?

                        Thanks a lot.

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                        • #87
                          Re: TangBand 75-1558SE on a Waveguide with Measurements

                          Originally posted by JochenM View Post
                          It was indeed on the first page ;)
                          Did you again use that slight 1/8" "ring" that was not routed away and that you've marked in the picture on page 1?

                          Thanks a lot.
                          Just realized I did not take any pictures last year when I built the final design. To your question: after routing the chamfer of the waveguide, I routed that ring away. Then I attached the foam where that ring was instead of to the driver flange like I showed in that first post. So basically the foam takes up the space better than the little ring did, which had a unavoidable small gap.
                          ~Brandon
                          Please donate to my Waveguides for CNC and 3D Printing Project!!
                          Please donate to my Monster Box Construction Methods Project!!
                          Soma Sonus

                          Comment


                          • #88
                            Re: TangBand 75-1558SE on a Waveguide with Measurements

                            Originally posted by augerpro View Post
                            Just realized I did not take any pictures last year when I built the final design. To your question: after routing the chamfer of the waveguide, I routed that ring away. Then I attached the foam where that ring was instead of to the driver flange like I showed in that first post. So basically the foam takes up the space better than the little ring did, which had a unavoidable small gap.
                            Thanks a lot, that was exactly what I wanted to hear ;)

                            I think I'm going to use gasket tape and maybe modeling clay for finetuning.

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