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  • #76
    Re: Open Baffle musings

    Originally posted by Mayhem13 View Post
    Have to disagree with you here Deward as most certainly a waveguide loaded ribbon/planer coupled to a cone woofer can result in an M/T with constant directivity. It's been done.
    Examples?
    "It suggests that there is something that is happening in the real system that is not quite captured in the models."

    Comment


    • #77
      Re: Open Baffle musings

      When we start talking about front and rear tweeters with dipole mids, I've analyzed it extensively. Here is a summary. Note that a single front tweeter radiating in to 2Pi space still yields up to 1.8dB more power than the dipole mid. Add a rear tweeter and you get as high a +4.8dB. Some how directivity control of the tweeter (or other source) is required.



      Also note in Fig 3 for a dipole tweeter with dipole mid. This is where the Note concept had it beginnings, right after the NaO II was introduced.


      Also, some where I read something about attenuation with distance, so I put this chart together. It shows that attenuation above 1k hz which would be required for the frequency response at 3 M to sound like that at 20 M. Of course, you would only consider doing this to yuor speakers it he recording was close miked in the first place. (Does not apply for old folks ;) )

      John k.... Music and Design NaO dsp Dipole Loudspeakers.

      Comment


      • #78
        Re: Open Baffle musings

        If the tweeter response is the issue with these dipole designs, why not put the tweeter into a waveguide and control the directivity that way since the flat baffle isn't helping?

        Heck, put a dipole tweeter into a symmetrical waveguide . . . )-( . . . where "-" is the tweeter diaphragm. The Aurum Cantus Aerostriction tweeters with their felt pads removed from the back would be ideal candidates for such an exercise.
        It seems to present some unusual challenges - not that any of this stuff isn't full of challenges, but these are again slightly different. I've all but given up on trying to keep things waveguide loaded through the mid (Neo10) and may swap to two Neo10's per side, if I can figure out how to manage the height issue. Sure makes the overall size smaller though (24" WG on the 10's seemed to be the requirement, and they work... ish.) I've tabled that project for the moment (again) while working through the Nebbiolo - lack of space to actually USE the end result is one significant problem anyhow. Still need to figure out what goes between the low end and the Neo10 too.

        But now you have me curious about the AC AS tweeters I have stashed... why? WHY?! Though I thought mine had a metal plate over the back. Perhaps I don't have the model you have in mind?

        C
        diVine Audio

        Comment


        • #79
          Re: Open Baffle musings

          A gumption trap is an event or mindset that can cause a person to lose enthusiasm and become discouraged from starting or continuing a project.

          http://en.wikipedia.org/wiki/Gumption_trap

          The term "analysis paralysis" or "paralysis of analysis" refers to over-analyzing (or over-thinking) a situation, or citing sources, so that a decision or action is never taken, in effect paralyzing the outcome.

          http://en.wikipedia.org/wiki/Analysis_paralysis

          Perhaps I am confusing musing and amusing, when I see "I've tabled that project for the moment (again)" I start to wonder about the usefulness of threads like these. Not many people are going to build something with $200 to $400 drivers with ever increasing complex design considerations. Maybe this inappropriate to place this here and we should start a dipoles for dollars thread:D

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          • #80
            Re: Open Baffle musings

            Originally posted by fdieck View Post
            Perhaps I am confusing musing and amusing, when I see "I've tabled that project for the moment (again)" I start to wonder about the usefulness of threads like these. Not many people are going to build something with $200 to $400 drivers with ever increasing complex design considerations. Maybe this inappropriate to place this here and we should start a dipoles for dollars thread:D
            Eh. I have parts for 4 speaker builds, one of which is the dipole I'm talking about here, and this project is one I've planned to take some time as I explore, find things I don't understand, and put it aside while I work on other projects and do more research while considering the next phase. It's how I work, not an indication of value. And since the project is very much for me (but fun to share) and half the fun of these things for me is the journey... I often only have half an hour here or there for this stuff. If I build something and somewhere else someone finds it and also builds it, all the better - but no loss if not.

            I long ago walked away from trying to do things on a budget. I just didn't like the results, and it DID prevent others from following the same path. Heck, I switched mid drivers for the Nebbiolo when the one I had on hand suddenly stopped being available.

            C
            diVine Audio

            Comment


            • #81
              Re: Open Baffle musings

              Originally posted by fdieck View Post
              I start to wonder about the usefulness of threads like these.
              There's alot to be said for not just duplicating previous failures, and not putting a lot of actual construction time (and money) into projects that are bound to fail. There are "ever increasing complex design considerations" because the issues being addressed are themselves increasingly complex, and increasingly on "the edge" of what we understand. That doesn't necessarily mean that the end result is going to be complex . . . the "physical manifestation" of LX521 is itself quite simple, and it requires no special skills to build. Figuring out how to solve complex problems with simple structures is complex, however, with lots of analysis needed to figure out the "whys" and "whats" . . .
              "It suggests that there is something that is happening in the real system that is not quite captured in the models."

              Comment


              • #82
                Re: Open Baffle musings

                Originally posted by cjd View Post
                It seems to present some unusual challenges - not that any of this stuff isn't full of challenges, but these are again slightly different. I've all but given up on trying to keep things waveguide loaded through the mid (Neo10) and may swap to two Neo10's per side, if I can figure out how to manage the height issue. Sure makes the overall size smaller though (24" WG on the 10's seemed to be the requirement, and they work... ish.) I've tabled that project for the moment (again) while working through the Nebbiolo - lack of space to actually USE the end result is one significant problem anyhow. Still need to figure out what goes between the low end and the Neo10 too.

                But now you have me curious about the AC AS tweeters I have stashed... why? WHY?! Though I thought mine had a metal plate over the back. Perhaps I don't have the model you have in mind?

                C
                Check out the review of the AST2560 here.

                http://www.parts-express.com/pe/show...number=276-440

                "I was told that it could not be used dipole. It can. I must warn that the back of the tweeter membrane is only protected with a thin felt strip. IF YOU USE THESE MONOPOLE YOU MUST MAKE A REAR CHAMBER. "
                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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                • #83
                  Re: Open Baffle musings

                  Check out the review of the AST2560 here.

                  http://www.parts-express.com/pe/show...number=276-440

                  "I was told that it could not be used dipole. It can. I must warn that the back of the tweeter membrane is only protected with a thin felt strip. IF YOU USE THESE MONOPOLE YOU MUST MAKE A REAR CHAMBER. "
                  Clearly I'm just not remembering right when I played with the tweeter. Come to think of it, I remember the felt and just did not pay attention enough to how it was built. Maybe that project should also be dipole... hmmmmmmm... verrrry tempting.
                  diVine Audio

                  Comment


                  • #84
                    Re: Open Baffle musings

                    Originally posted by Deward Hastings View Post
                    There's alot to be said for not just duplicating previous failures, and not putting a lot of actual construction time (and money) into projects that are bound to fail. There are "ever increasing complex design considerations" because the issues being addressed are themselves increasingly complex, and increasingly on "the edge" of what we understand. That doesn't necessarily mean that the end result is going to be complex . . . the "physical manifestation" of LX521 is itself quite simple, and it requires no special skills to build. Figuring out how to solve complex problems with simple structures is complex, however, with lots of analysis needed to figure out the "whys" and "whats" . . .
                    ........paralysis!!! The existing state of the art is "duplicating previous failures"? Don't confuse NIH (not invented here) for progress. In 1969 we went to the moon, and not by saying we should think about how to do it for a couple decades. HARRY Truman famously asked to be sent a one-armed economist, having tired of exponents of the dismal science proclaiming "On the one hand, this" and "On the other hand, that".

                    How do "not putting a lot of actual construction time" and "LX521 is itself quite simple, and it requires no special skills to build" show
                    up in the same argument? The only bound to fail I see is the elitism and defeatism of never having to commit to building something because it might not be state of the art. By this reasoning the NaO Note and the LX521 are failures and we sound sit around and wait years till the designs and new driver technology catch up. To paraphrase Oscar Wilde "There only one worse than talking about speakers and that is not building the speakers talked about." There is a saying "It is time to shoot the engineer and ship the product.

                    Comment


                    • #85
                      Re: Open Baffle musings

                      Well...... I've done it now.

                      Comment


                      • #86
                        Re: Open Baffle musings

                        Originally posted by fdieck View Post
                        Well...... I've done it now.
                        What are you going on about? Get that soap out of your mouth! :D

                        Fact is that the key elements of successful full range dynamic dipole loudspeaker design are now in place. What’s left are merely details, variations on the theme. Thanks to the pioneering work of SL, who essentially invented the genre and provided the pre-eminent design examples for each step of its evolution, and the design refinements and variations done by John K and others (including a number of German and Australian experimenters not much noted in the US), we know what it takes to succeed with such a design, and anyone familiar with the form can sketch out a reasonable working example. Equally important we know what variations don’t work, and have a pretty good idea why. Of course there’s room for improvement and variation around the basic design (the devil is *always* in the details). But compromising too far on any of the basic design elements will produce a speaker that is so significantly flawed that it’s not worth doing.

                        You’ll know one when you see one.

                        The design is going to be 4-way. Unless you use an AMT or planar elements on the top end that’s just how it is. Trying for 3-way compromises too much else.

                        The woofer is going to be long throw and in a “frame” of some sort. A flat baffle large enough to be useful is too big to be practical in almost any room. This all but eliminates the possibility of getting woofer response up to 300Hz., one of the (almost) necessary steps for a successful 3-way.

                        The mids are going to be 8” and 3”, give or take an inch or two, and they are going to be on narrow (stepped or tapered) baffles for pattern control.

                        The tweeter(s), and getting a reasonably symmetrical and dipole-like pattern out of them, are the detail where the Devil seems to be residing these days. There are several options which probably work well enough.

                        Crossover and equalization is going to be active, either digital (see John K) or analog with perhaps one “passive” element (see SL or John K). There is no practical way to implement a satisfactory full-range “passive” design, and no reason to try.

                        While it is certainly possible to produce “open baffle” designs that stray beyond the characteristics stated above they will almost certainly not be “dipole”, and will not give the directivity control that is an essential element and goal of all dipole designs.

                        So . . . there you have it. Get out there and start building. Cut some baffles, mount some drivers, let us know how it sounds when you’re done.
                        "It suggests that there is something that is happening in the real system that is not quite captured in the models."

                        Comment


                        • #87
                          Re: Open Baffle musings

                          Actually, Olson was the was the pioneer and invented the genre. What followed is built upon his work.

                          John k.... Music and Design NaO dsp Dipole Loudspeakers.

                          Comment


                          • #88
                            Re: Open Baffle musings

                            Originally posted by johnk... View Post
                            Actually, Olson was the was the pioneer and invented the genre.
                            What speakers did he design and build? I was actually around and doing audio "stuff" in the 60's and 70's, and apart from KLH and Quad (both from the mid 50's, and substantially predating Olson) and Magnepan I don't recall any dipole designs . . . certainly not with "dynamic" drivers. When the Audio Artistry speakers first appeared (just about contemporary with Von Schweikert, as I recall) the almost universal response was to the "novelty" of it. They were compared (as dipoles) to the large "panel" dipoles, but to nothing else, because there was nothing else.

                            The Olson article is an interesting artifact of history (and you can find reference to dipole radiators in acoustics books and articles even from the 30's), but it does not appear to have played a significant role (if any role at all) in the arc of current dynamic driver dipole loudspeaker design.
                            "It suggests that there is something that is happening in the real system that is not quite captured in the models."

                            Comment


                            • #89
                              Re: Open Baffle musings

                              Ah, look what I put together this afternoon:

                              Click image for larger version

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                              Why, it's one of those open baffle speakers... I'm calling this project the "MWOB" for medium width open baffle. I'm just not very creative when it comes to naming my projects I'm afraid.

                              Drivers are:
                              MIDWOOFER: Exodus Anarchy
                              TWEETER: Tang-Band W2-800SL
                              BAFFLE: 24"W, 48" H

                              Here is the frequency response measurement after some very preliminary crossover development:
                              Click image for larger version

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                              I took some measurements and did some diffraction sims, then I imported the measurements into ACD, figured out the acoustic offset, and then created the OB compensation filters for both drivers. Preliminary crossover is a simple LR2 at 750 Hz.

                              Here is the FR measurement (white trace) imported into ACD and overlaid with the ACD System Response (blue trace) as well as the driver responses. Excellent agreement between ACD and measurement...
                              Click image for larger version

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                              -Charlie
                              Last edited by charlielaub; 11-17-2012, 10:13 PM. Reason: Fixed the attached images.
                              Charlie's Audio Pages: http://audio.claub.net

                              Comment


                              • #90
                                Re: Open Baffle musings

                                Originally posted by Deward Hastings View Post
                                What speakers did he design and build? I was actually around and doing audio "stuff" in the 60's and 70's, and apart from KLH and Quad (both from the mid 50's, and substantially predating Olson) and Magnepan I don't recall any dipole designs . . . certainly not with "dynamic" drivers. When the Audio Artistry speakers first appeared (just about contemporary with Von Schweikert, as I recall) the almost universal response was to the "novelty" of it. They were compared (as dipoles) to the large "panel" dipoles, but to nothing else, because there was nothing else.

                                The Olson article is an interesting artifact of history (and you can find reference to dipole radiators in acoustics books and articles even from the 30's), but it does not appear to have played a significant role (if any role at all) in the arc of current dynamic driver dipole loudspeaker design.

                                Jeez Deward, give it a rest. We all know you are an unrecognized genius among us, but you've got to give some
                                credit to the pioneers (and dare I say, giants) -

                                Harry Olson, Music Physics and Engineering 1952.
                                Still on MY bookshelf as a standard reference.

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