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  • A question of

    I recently heard an electrostatic loudspeaker that was approximately 24" wide and 60" tall. That gives the entire panel around 1440 square inches of air moving capability not including the minimal excursion of the panel, which is a fraction of an inch.

    For the sake of argument lets use the Dayton ST385-8 15" Series II Woofer (http://www.parts-express.com/pe/show...number=295-130) to compare. It has an Sd of 850.1 square centimeters which equates to 131.76 square inches.

    I know Xmax is an issue here, but how does one effectively move as much air as the large panel with a dynamic driver?

    Thanks!
    Last edited by Ross123; 04-06-2009, 01:21 PM. Reason: clarification on post title

  • #2
    Re: A question of

    There is no replacement for displacement. I also assume that these ESL panels have next to no x-max, since they are not known for bass.

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    • #3
      Re: A question of

      That is part of my question.

      Since the electrostatic panels have so much more area are they not moving more air until the excursion of the 15" woofer in conjunction with its Sd equals or overcomes the excursion limits of the panel?

      20 Hz is the act of moving back and forth 20 times a second. Is there a minimal excursion limit required for 20 Hz to have any meaningful output? On the other hand the panel with its over 1400 square inches of panel should have at least some bass since its area is so large despite its minimal excursion capabilities.

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      • #4
        Re: A question of

        Don't neglect dipole cancellations with a large panel. At lower frequencies, the positive pulse from the front is partially cancelled by the negative wave from the back.

        Makes me wonder if anyone has mounted a panel into a wall (i.e. infinite baffle) to see what bass they might attain.
        Bill Schneider
        -+-+-+-+-
        www.afterness.com/audio

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        • #5
          Re: A question of

          williamrschneider,

          You are correct however, there is still a large panel firing directly ahead that moves air. I too, think it would be a cool project to put an electrostatic panel in a wall:-)

          I believe the in order for a loudspeaker to be true to the musical event one of the many factors should be that an appropriate amount of air must be moved. I disagree with large excursion drivers. I like the idea of moving air effectively without launching a driver cone though inch of acoustic air space in one direction. The electrostatic panel moves a large amount of air very effectively and with finesse.

          Is there something I am missing when desiring to use dynamic drivers to move a similar amount air but without high excursion?

          Comment


          • #6
            Re: A question of

            Originally posted by Ross123 View Post
            williamrschneider,

            You are correct however, there is still a large panel firing directly ahead that moves air. I too, think it would be a cool project to put an electrostatic panel in a wall:-)

            I believe the in order for a loudspeaker to be true to the musical event one of the many factors should be that an appropriate amount of air must be moved. I disagree with large excursion drivers. I like the idea of moving air effectively without launching a driver cone though inch of acoustic air space in one direction. The electrostatic panel moves a large amount of air very effectively and with finesse.

            Is there something I am missing when desiring to use dynamic drivers to move a similar amount air but without high excursion?
            I just wonder whether or not the ESL has the tensile strength to last on high bass passages. It sounds like an expensive experiment.

            Comment


            • #7
              Re: A question of

              Which panels are you describing? Those are the same dimensions as the Kingsound Prince's that I heard a few weeks ago. They had a surprising amount of bass compared to the smaller Maggies I've heard. It wasn't exactly kick you in the chest bass, but they did go pretty deep.
              "He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche

              http://www.diy-ny.com/

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              • #8
                Re: A question of

                It was an older pair of Soundlab speakers. I have heard their very large panels before and yes, they have the capability to create a respectable bass.

                I generally do not like dipole speakers and I do not like electrostatics but I was pondering the amount of air being moved by the panels versus dynamic drivers.

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                • #9
                  Re: A question of

                  I think you have all outlined the debate of panel vs. dynamic. In this case the final analysis is more than specs like moving air. I have owned Magnepans with Ribbons and Carvers with Dynamic woofers and Ribbons. My observation is that there is an airiness and large "lifesize" soundstage that no dynamic speaker can touch. It's the Combination of fast transient response, dipole ambiance and the inherent phase coherence of all frequencies coming from a single source simultaneously. And by the way the larger Maggie panels do produce decent bass.

                  BUT... the ups and downs are as large as the panels! Setup is so critical. With the distance required from rear and side walls and the head-size sweet spot you need a dedicated single purpose 20x30 room with one chair and room for the Amplifiers. Huge amounts of quality Amplifier power are needed and will cost as much as the speakers themselves. And with all that power you will still run out of dynamic range at relativly low SPL due to the small excursion limits. In the interest of marital compromise and practicality I had to say goodbye to panels. In addition to some project speakers and Subs now have Thieles in the main system. Bob Thiele has some of the best designs using dynamic drivers and has always paid great attention to phase coherence. They can only approach the Maggies and Ribbons in airiness but they are smooth, accurate, have that satisfying bass punch and dynamic range that I missed with panels.

                  Having said all that, if I had the money and an extra huge room to dedicate to panels I would do it. Jazz with string bass, close miced female vocals, The Cello in a Chamber string ensemble, Nylon Acoustic guitar, a full orchestra stretched out across your listening room. NOTHING does that like Panels and ribbons.

                  Just my 2 cents
                  CC

                  Comment


                  • #10
                    Re: A question of

                    thank you all for your answers, but none, so far have addressed my question. I have experience with all types of speakers, electrostatics (big and small), Magnepan (big and small), MBL omnidirectional, horns, dynamic transducers, etc. I really do not care about the subjective differences. My question is what part of the equation do I feel I am missing when calculating the amount of air moved for a dynamic driver versus a large panel type speaker?

                    As I stated in my original post, the panel was 24" x 60" which equals 1440 square inches of diaphragm. A 15" woofer has 131.76 square inches. Now these numbers represent a diaphragms at rest. At what point will dynamic cone drivers move the same amount of as the 1440 square inches of mylar in the electrostatic. Does one need 10-12 15" woofers to equal the air moving capability? Does one need only 1 woofer once you account for excursion?

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                    • #11
                      Re: A question of

                      Originally posted by Ross123 View Post
                      thank you all for your answers, but none, so far have addressed my question. I have experience with all types of speakers, electrostatics (big and small), Magnepan (big and small), MBL omnidirectional, horns, dynamic transducers, etc. I really do not care about the subjective differences. My question is what part of the equation do I feel I am missing when calculating the amount of air moved for a dynamic driver versus a large panel type speaker?

                      As I stated in my original post, the panel was 24" x 60" which equals 1440 square inches of diaphragm. A 15" woofer has 131.76 square inches. Now these numbers represent a diaphragms at rest. At what point will dynamic cone drivers move the same amount of as the 1440 square inches of mylar in the electrostatic. Does one need 10-12 15" woofers to equal the air moving capability? Does one need only 1 woofer once you account for excursion?
                      Total displacement can be calculated in cubic in. This is the true measurement of volume dispalcement. This is the only way to judge equivalency. This assumes that there is no cancellation at play. I am guessing that an electrostatic has about 1/10th the x-max of a normal woofer.

                      SD * xmax = tD (Total Displacement)

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                      • #12
                        Re: A question of

                        The ribbon likely has at most .5mm (0.02in) of excursion, so the moving volume at capacity would be 1440x0.02 = 28.8 cubic inches
                        0.5mm for a ribbon might even be overly optimistic.

                        A 15" driver with a 13.75" piston diameter and 8mm (0.315in) excursion, has 46.7 cubic inches of volume at it's rated xmax. So the 15 is moving a lot more air. Combine this with dipole cancellation at low frequencies and the 15 is capable of producing a lot more bass.

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                        • #13
                          Re: A question of

                          Thank you!

                          I knew something was wrong with my thinking.

                          Thanks again.

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