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  • Next Up: Omni redux

    About 6 years ago I embarked on an interesting design for an omni speaker that combined elements of omni midrange with bipole woofers and a sort of bipole/waveguide tweeter. The project ended up with the name of Contrappeso’s. For those who have not seen or heard these speakers, they throw a huge soundstage, yet have some decent imaging and can get very loud, due to the number of drivers employed plus the boost provided by the waveguide to the tweeter. They included dual front/rear 12” buyout sealed woofers, 4 mids in two tubes, each tube with an up and down facing mid with the tweeter firing toward the sides of the two tubes that forming a front and rear waveguide. So there were 7 drivers per speaker. They were an unusual looking, but oddly effective speaker. These were the last omni speaker I did.



    I’ve always intended to revisit that design to see if I could come up with something that took a little less physical territory when deployed, worked as effectively and, well, looked a litter higher class. I even picked up some aluminum tubes for a new version a few years ago that I never did anything with. Recently I had the urge to revisit that design and have been conceptualizing, trying to come up with something that I could move forward with. Below is what I have come up with, final color scheme to be determined.





    Drivers: (total of 6 or 7 per speaker, number to be determined)

    Woofer: 1 - Aura NS10, 10” subwoofer. I picked up 4 of these for a song. They have good sensitivity for a subwoofer, yet reach pretty low in a reasonably small ported box. They measure quite flat out to above 2kHz or so, iirc. Mounted on a wide baffle, near the floor, there should be no need for bsc, so a single driver should yield an electrical sensitivity of around 90 db, 2.83v/meter. Modeling in Diffraction and Boundary Simulator, the low end boundary gain is approaching 9db, when about 3’ from the front wall. The graph below shows the modeled woofer response in box and with boundary reinforcement. Also shown is the anticipated mid output with 4 mids in a series/parallel configuration with 1 ohm resistance in series. Overall, this should make for a pretty sensitive speaker, one that will never reach the excursion limits of the single woofer until below 20Hz, at least in my use. In this case, the 53L box is tuned to around 23Hz, with an in room F3 anticipated at about 18Hz.

    Midrange: 4 – Dayton Audio DS90-8, 3” extended range in a series/parallel configuration:http://www.parts-express.com/dayton-...8-ohm--295-422



    Tweeter: http://www.parts-express.com/peerles...-ohm--264-1122

    Phsyical Design:

    Mid/Tweeter Module.Woofer Cabinet. I needed around 50L to get solid, ported extension into the low 20’s, but at the same time I didn’t want the box to have too significant an impact on the output and dispersion of the mids or create reflections that would bounce back up at the down firing midrange. I came up with the idea of creating a narrow triangular shaped profile, with the pinnacle close to the tubes. The front to back position of the tube stack is currently placed so that the voice coils come close lining up to equidistant from the seated ear at about 12’ away. The box shape evolved to allow for 53 liters, with dual triangular ports built into the corners so that two of the three port walls are formed by the sides of the box, minimizing volume displacement. Then an arm shape was determined to suspend the tubes above the woofer cabinet, with the arm structure being incorporated into the speaker base. I envision it being built out of laminated plywood, with perhaps some vibration reducing material encased. Wires will run within from the crossover mounted in the woofer cab.



    Crossover Design:

    Much has to be determined once measurements are taken, but I don’t expect anything unique or unusual. It is nearly impossible to simulate the frequency response of either the mid stack or the tweeter(s)/waveguide module. Going in, I anticipate the crossovers to be in the 300-400Hz range and 3000-4000Hz range. The drivers may be able to handle 2nd order in these ranges, which will likely be my starting point.

    That’s all for now. I haven’t thought about a project name yet. I’m not sure when I will get started on these, nor am I anxious to get out in the garage this time of year. It is unlikely that these will make it to any of the early or mid-year events, however. My project production is ramping down big time. I’m not sure how many more speakers I will be inspired to build.
    Feel free to comment, good, bad or otherwise!
    Dan N.

  • #2
    Another masterpiece, I'm sure.

    Comment


    • #3
      I think I like the red or blue color the best.
      I'm sure another impressive design. Those ns10s should be potent.
      - Ryan

      CJD Ochocinco ND140/BC25SC06 MTM & TM
      CJD Khanspires - A Dayton RS28/RS150/RS225 WMTMW
      CJD Khancenter - A Dayton RS28/RS150/RS180 WTMW Center
      CJD In-Khan-Neatos - A Dayton RS180/RS150/RS28 In/On Wall MTW

      Comment


      • #4
        Looking forward to this Dan. The Contrapessos are probably my favorite design of yours. I temember being shocked by the soundstage when I heard them.

        Dan
        _____________________________
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        • #5
          Pretty amazing looking. The bass unit -- on my computer at least -- look metallic. With the sharp angle and point at the top, maybe something knife-like would be in order name-wise? I'm lousy at naming things so no help there.

          ​You seem to do around one really big/complicated build per year, plus a few extras last year as a SBDT member... that's a lot of speakers really with one of them being a mega-build. I'm impressed with your ability to stay focused to your projects at hand and not get crazy with too many projects going on. "Do one thing, do it very well, then move on" --Charles Emmerson Winchester, III if I'm not mistaken.

          ​TomZ
          *Veneering curves, seams, using heat-lock iron on method *Trimming veneer & tips *Curved Sides glue-up video
          *Part 2 *Gluing multiple curved laminations of HDF *Cello's Speaker Project Page

          *Building the "Micro-B 2.1 Plate Amplifier -- Part 1 * Part 2 * Part 3 * Part 4 * * Part 5 'Review' * -- Assembly Instructions PDF

          Comment


          • #6
            A true innovator - and another masterpiece in the making.
            I've been thinking a lot about omni speakers recently - given the limitations of arrays / OB.
            A stable, large sound stage is very appealing to me.

            I think I hear a difference - wow, it's amazing!" Ethan Winer: audio myths
            "As God is my witness I'll never be without a good pair of speakers!" Scarlett O'Hara

            High value, high quality RS150/TB28-537SH bookshelf - TARGAS NLA!
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            Tangband W6-sub

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            • #7
              Haven't heard your earlier omni design, but looking forward to hearing these. How are you going to take the measurements?

              Comment


              • #8
                Thanks for the supportive commenrts, gents.

                Originally posted by ---k--- View Post
                I think I like the red or blue color the best.
                I'm sure another impressive design. Those ns10s should be potent.
                My opinion on color is not as important as it used to be!
                Dan N.

                Comment


                • #9
                  Originally posted by DanP View Post
                  Looking forward to this Dan. The Contrapessos are probably my favorite design of yours. I temember being shocked by the soundstage when I heard them.

                  Dan

                  I didn't know that. I always liked them a lot as well. They are fun to listen to and boy will they get loud if you want to go there..
                  Dan N.

                  Comment


                  • #10
                    Originally posted by tomzarbo View Post
                    Pretty amazing looking. The bass unit -- on my computer at least -- look metallic. With the sharp angle and point at the top, maybe something knife-like would be in order name-wise? I'm lousy at naming things so no help there.

                    ​You seem to do around one really big/complicated build per year, plus a few extras last year as a SBDT member... that's a lot of speakers really with one of them being a mega-build. I'm impressed with your ability to stay focused to your projects at hand and not get crazy with too many projects going on. "Do one thing, do it very well, then move on" --Charles Emmerson Winchester, III if I'm not mistaken.

                    ​TomZ
                    I haven't even contemplated a name. Sometimes they come to me, but not often. I have already used "Blades" and "Scimitars" so I probably need to find another avenue for a name this time.
                    Yeah, I gravitate toward complicated builds and suffered major burnout after last year, so I'm not in any hurry to start these..
                    Dan N.

                    Comment


                    • #11
                      Originally posted by donradick View Post
                      A true innovator - and another masterpiece in the making.
                      I've been thinking a lot about omni speakers recently - given the limitations of arrays / OB.
                      A stable, large sound stage is very appealing to me.
                      I've always been drawn to big soundstages and fjnd pinpoint imaging to be much less important than soundstage size and depth to me personally.
                      Dan N.

                      Comment


                      • #12
                        Cool concept Dan. They don't appear to be any lighter than previous builds and I did notice you managed to slip in one 90 degree cut

                        WRT color it might be interesting to flip the wood to the base (bass) cabinet and the support arm to metal.
                        John H

                        Synergy Horn, SLS-85, BMR-3L, Mini-TL, BR-2, Titan OB, B452, Udique, Vultus, Latus1, Seriatim, Aperivox,Pencil Tower

                        Comment


                        • #13
                          Originally posted by ani_101 View Post
                          Haven't heard your earlier omni design, but looking forward to hearing these. How are you going to take the measurements?
                          In my experience, you can measure most omni's in the direction of the listening position and get a pretty good result. I think that is because you don't generally have to deal with the issues that are caused by the beaming of drivers as they transition into 2pi space and then change to 4pi at the crossover point the next driver. A good omni presentation will measure much the same at all horizontal axis points, which suggests a single measurement is therefore more representative of what the power response will be than a single measurement with a monopole would represent. In this case the tweeters are an unusual blend of controlled directivity from the waveguided tweeter, but then you have the exact same response to the rear.
                          Dan N.

                          Comment


                          • #14
                            Originally posted by jhollander View Post
                            Cool concept Dan. THey don't appear to be any lighter than previous builds and I did notice you managed to slip in one 90 degree cut

                            WRT color it might be interesting to flip the wood to the base (bass) cabinet and the support arm to metal.

                            I may play around with that, John. The shape is pretty much set, but the finish is not at all. The problem with wood on a shape like this, as I see it, is you can't wrap the veneer like you can a box with parallel sides and it is rather a pain to get the little chamfers and so on glue and trimmed, which generally makes paint a more attractive solution.

                            Not sure if you meant a real metal arm (or simply metal look), but that is an interesting idea in that it could be much thinner and therefore have less real estate in the way of the down facing drivers dispersion and less chance for edge diffraction and reflections. Aluminum could be cool, but very expensive,
                            Dan N.

                            Comment


                            • #15
                              Very interesting build. I had the same thought about the arm.... that it should be aluminum. Just my two cents.

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