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  • bradley.s
    replied
    There's a 2016 paper titled, "Optimized Driver Placement for Array-Driven Flat-Panel Loudspeakers" by David A. ANDERSON, Michael C. HEILEMANN, Mark F. BOCKO, but it's located at an unsecure link.

    It's also too large to upload as an attachment.

    "The recently demonstrated ‘modal crossover network’ method for flat panel loudspeaker tuning employs an array of force drivers to selectively excite one or more panel bending modes from a spectrum of panel bending modes. A regularly spaced grid of drivers is a logical configuration for a two-dimensional driver array, and although this can be effective for exciting multiple panel modes it will not necessarily exhibit strong coupling to all of the modes within a given band of frequencies. In this paper a method is described to find optimal force driver array layouts to enable control of all the panel bending modes within a given frequency band. The optimization is carried out both for dynamic force actuators, treated as point forces, and for piezoelectric patch actuators. The optimized array layouts achieve similar maximum mode coupling efficiencies in comparison with regularly spaced driver arrays; however, in the optimized arrays all of the modes within a specified frequency band may be independently addressed, which is important for achieving a desired loudspeaker frequency response. Experiments on flat panel loudspeakers with optimized force actuator array layouts show that each of the panel modes within a selected frequency band may be addressed independently and that the inter-modal crosstalk is typically −30 dB or less with non-ideal drivers."

    "6. Conclusion A method was described for finding the optimal force actuator locations for controlling a selected set of bending modes of a flat panel. In the applications of specific interest in this paper (flat panel loudspeakers) it is important to be able to exert independent control over each of the modes in a low-pass frequency band. The geometry of the modes in such a set may vary greatly, which implies that the layout of the actuator array that would be most effective at driving each mode is unique, since a mode is driven most effectively by actuators near a mode’s antinodes. An optimization method was employed to determine the actuator locations that are able to drive every mode in a selected set as equally as possible and to spread the work evenly among the force actuators in the array. Simulations show that either point-force actuators or piezoelectric bending actuators have global optima that give large coupling efficiency between the actuators and modes."

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  • bradley.s
    replied
    Here's a different paper titled, "Optimized Driver Placement for Array-Driven Flat-Panel Loudspeakers"

    http://www.czasopisma.pan.pl/Content...-2017-0010.pdf

    Leave a comment:


  • geosand
    replied
    Well I think its good to see that the tech is still being researched...The science (computational modelling), the measurements and the build techniques are all needed to progress in the design. Here's the latest on Optimal exciter placement: http://www.aes.org/e-lib/browse.cfm?elib=20277 ... too bad its only behind a pay wall. I wonder how the usual 2/5|3/5 rule matches their computational methods...

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  • Unbiasedsound
    replied
    Originally posted by bradley.s View Post

    True, the paper didn't discuss that. On the other hand, both Tectonic and Billionsound stabilize the exciter. Consequently, I lean toward stabilizing the exciters.
    One of the main reasons I believe it was a failure is because it didn't use a spline to stabilize the exciter.

    Leave a comment:


  • Unbiasedsound
    replied
    Damn I had a great reply to Kornbread but once again it didn't go through. SIGH.

    Tectonics design is not the same as maps design in that article. SMDH If you could compare Tectonics panels to that map articles panels they wouldn't sound the same nor would they even measure the same. Using more then one exciter per panel has been done buy others including myself but it don't make it that MAP design in that particular article.

    Leave a comment:


  • Unbiasedsound
    replied
    Originally posted by Kornbread View Post
    The problem is I don't have the money or the time to try experiments like MAP that I feel leads to nowhere. I will let someone else do the dirty work and if and when it does work I will try it. Until then I rather concentrate on techniques that have proven to be successful.

    Since around 4 years ago when I first started with these panels I have spent over 2k on experiments. Today I have gotten to a point where I am satisfied and happy with the sound quality of my panels. If back then I knew what I know now my expenses would have been less then $300.00. LOL

    What I don't understand is that I don't see many (if any at all) people trying to mimic successful DML designs like the Podiums, Bertagni's,yamaha's etc etc. A lot of techniques I am giving out actually comes from these successful designs. For example one technique I mentioned is to put a piece of damping material right on the back of the exciter or on the spline, this technique comes from Shell katz and his Podiums.

    What I want to know about maps design is where are the reviews of MAPs panels sound quality? Who here has ever heard that particular MAP dml design? If it was so great why wasn't it marketed? Does one even know if that MAP design was a successful or failed attempt at producing a good sounding panel? Its been almost 10 years since they did the MAP experiment, WHERE ARE THEY NOW and what have they produced? With so little or limited info on this design I personally wouldn't even take chance on it.

    Bertagni used the technique (in the 60's) of stabilizing the exciter in place with a spline because he new that the magnet needed to be held in place so the voice coil would only push the panel material its just plain (Dr.Jose Bertagni was a physics professor) physics. With heavy bass tracks the exciter uses more pistonic motion there fore it needs something to push off of like a spline. Anyone play the push hands game? Well if one person is leaning against a wall and the other person isn't the person leaning on the wall will always win because the wall acts as a brace/spline so he can stabilize him self to push off of. Also like I mentioned before that without a spline to hold and stabilize the exciter in place the magnet will move and that rattling sound you are hearing is coming from the magnet moving especially at higher bass excursions.

    Oh my bad just rambling. LOL

    The research paper referenced is "a technical review of the development of a special type of planar loudspeaker array for wave field synthesis, known as multiactuator panel". It is not add hype for some new speaker manufacturer. It is a fact based research paper that simply lays groundwork for others to build upon if they choose to do so. I for one am glad it, and similar research, has been freely shared and encourage others to continue the vibrating panel experiment.

    Great things have arisen from failure.


    On to sound quality. I am one of those that believes there are some things we cannot measure but can hear, but I also feel 95ish'% of what we can hear can be measured. Most people on this forum want to see measurements, not hear someone gush over how there latest creation is so much more betterer than anything else everer. That tells us very little about how a product actually sounds.

    Repeatable, accurate, and real measurements please. Everyone has a laptop, calibrated mics are not that expensive and there's some very accurate low-cost/free software (REW is one of many) floating around the net.
    Special type? What makes it so special? It is nothing new as I have tried multiactuators and so have many others. Built upon what a failure? Unless I had all the money and time in the world its not encouraging to continue someone elses failure.


    Greater things have arisen from ones success. That is why people patent things that are successful because they don't want others to steal there design. Not many patent a failure. LOL


    Most people or should I dare say ALL people buy speakers based solely on how they SOUND....I highly doubt a few if any at all buy speakers based solely on there measurements.....If not then at any DIY event no one needs to bring there speakers to listen to all you need is to compare measurements since 95% of it can be measured. LOL IN REALITY the last word is basically how a speaker SOUNDS. It seems people now days don't rely on there senses much instead rely on science in place of there senses. LOL

    As you already know I've been doing DML panels for around 4 years now and almost every forum or thread I read most people are so caught up in measurements that there panels never improve because measurements don't mean **** at telling one how to make there panels sound better. LOL You could post all the measurments in the world but will that make ones panel sound better? HECK NO. LOL

    What will make your panels sound better is if one follows certain TECHNIQUES.

    So while you are anticipating measurements I am anticipating a proven successful techniques that will actually improve sound quality of DML panels.

    Leave a comment:


  • bradley.s
    replied
    Originally posted by Kornbread View Post
    Something along this same area of thought is that there is no mention of stabilizing the exciter (actuator). In personal experiments, there was another large measurable increase in sound output, especially noticeable with music containing bass, when the back of the exciter was glued to a 'spine' effectively anchoring the exciter to the wood frame supporting the panel. The exciters like a solid footing.
    True, the paper didn't discuss that. On the other hand, both Tectonic and Billionsound stabilize the exciter. Consequently, I lean toward stabilizing the exciters.

    Leave a comment:


  • bradley.s
    replied
    Originally posted by Kornbread View Post

    Zero of my experiments used any kind of baffle and according to this paper they acted as a normal dipole. I agree, sound output 90* to the side was minimal, but isn't less interaction with room boundaries what we desire in a normal listening room? It comes at a cost.
    Yes. But you're designing for small rooms like most of us. They were concerned with large rooms with a few side references to small rooms. Large rooms don't have reflection problems. So, I'd tend to think dipole is a better design for small rooms. At the same time, I'll keep Geddes' room reflection in mind as well as Toole's. I'll put the speakers in the center of the room and five feet or more away from the rear wall. Then I'll move them out to Toole's 60 degree off-axis listening positions.

    Personally, I want speaker plane cancellation in the hopes it will reduce sidewall reflections.

    Leave a comment:


  • bradley.s
    replied
    Tectonic sells MAPs. These have eight exciters per panel. https://www.tectonicaudiolabs.com/pr...id=product-805

    Billionsound also uses MAPs for their subwoofers. http://www.billionsound.com/products...uctId=380.html

    Keele said some things that make me think separated MAPs might work. He also found a straight array can behave like a curved array starting on page 23 of this paper. https://www.xlrtechs.com/dbkeele.com...0Paper%205.pdf

    Something I'm interested to find out is what happens when a MAP CBT straight array radiates to both the front and the rear. Earl Geddes said you need a minimum of 10ms delay on rear and side reflections. So far, every CBT I've seen is enclosed and radiates to the front.

    The one thing most hi-fi audio DIYers are dealing with is small rooms. Thankfully, Floyd Toole, Earl Geddes, and Don Keele have provided some evidence based strategies to deal with small rooms. The authors of the 2010 paper provided evidence based strategies for multiactuator panels. Somewhere in all that research a good small room MAP design exists.

    Leave a comment:


  • Kornbread
    replied
    The problem is I don't have the money or the time to try experiments like MAP that I feel leads to nowhere. I will let someone else do the dirty work and if and when it does work I will try it. Until then I rather concentrate on techniques that have proven to be successful.

    Since around 4 years ago when I first started with these panels I have spent over 2k on experiments. Today I have gotten to a point where I am satisfied and happy with the sound quality of my panels. If back then I knew what I know now my expenses would have been less then $300.00. LOL

    What I don't understand is that I don't see many (if any at all) people trying to mimic successful DML designs like the Podiums, Bertagni's,yamaha's etc etc. A lot of techniques I am giving out actually comes from these successful designs. For example one technique I mentioned is to put a piece of damping material right on the back of the exciter or on the spline, this technique comes from Shell katz and his Podiums.

    What I want to know about maps design is where are the reviews of MAPs panels sound quality? Who here has ever heard that particular MAP dml design? If it was so great why wasn't it marketed? Does one even know if that MAP design was a successful or failed attempt at producing a good sounding panel? Its been almost 10 years since they did the MAP experiment, WHERE ARE THEY NOW and what have they produced? With so little or limited info on this design I personally wouldn't even take chance on it.

    Bertagni used the technique (in the 60's) of stabilizing the exciter in place with a spline because he new that the magnet needed to be held in place so the voice coil would only push the panel material its just plain (Dr.Jose Bertagni was a physics professor) physics. With heavy bass tracks the exciter uses more pistonic motion there fore it needs something to push off of like a spline. Anyone play the push hands game? Well if one person is leaning against a wall and the other person isn't the person leaning on the wall will always win because the wall acts as a brace/spline so he can stabilize him self to push off of. Also like I mentioned before that without a spline to hold and stabilize the exciter in place the magnet will move and that rattling sound you are hearing is coming from the magnet moving especially at higher bass excursions.

    Oh my bad just rambling. LOL

    The research paper referenced is "a technical review of the development of a special type of planar loudspeaker array for wave field synthesis, known as multiactuator panel". It is not add hype for some new speaker manufacturer. It is a fact based research paper that simply lays groundwork for others to build upon if they choose to do so. I for one am glad it, and similar research, has been freely shared and encourage others to continue the vibrating panel experiment.

    Great things have arisen from failure.


    On to sound quality. I am one of those that believes there are some things we cannot measure but can hear, but I also feel 95ish'% of what we can hear can be measured. Most people on this forum want to see measurements, not hear someone gush over how there latest creation is so much more betterer than anything else everer. That tells us very little about how a product actually sounds.

    Repeatable, accurate, and real measurements please. Everyone has a laptop, calibrated mics are not that expensive and there's some very accurate low-cost/free software (REW is one of many) floating around the net.

    Leave a comment:


  • Unbiasedsound
    replied
    Double post because my first post above got erased.
    Last edited by Unbiasedsound; 07-08-2019, 07:34 PM.

    Leave a comment:


  • Unbiasedsound
    replied
    The problem is I don't have the money or the time to try experiments like MAP that I feel leads to nowhere. I will let someone else do the dirty work and if and when it does work I will try it. Until then I rather concentrate on techniques that have proven to be successful.

    Since around 4 years ago when I first started with these panels I have spent over 2k on experiments. Today I have gotten to a point where I am satisfied and happy with the sound quality of my panels. If back then I knew what I know now my expenses would have been less then $300.00. LOL

    What I don't understand is that I don't see many (if any at all) people trying to mimic successful DML designs like the Podiums, Bertagni's,yamaha's etc etc. A lot of techniques I am giving out actually comes from these successful designs. For example one technique I mentioned is to put a piece of damping material right on the back of the exciter or on the spline, this technique comes from Shell katz and his Podiums.

    What I want to know about maps design is where are the reviews of MAPs panels sound quality? Who here has ever heard that particular MAP dml design? If it was so great why wasn't it marketed? Does one even know if that MAP design was a successful or failed attempt at producing a good sounding panel? Its been almost 10 years since they did the MAP experiment, WHERE ARE THEY NOW and what have they produced? With so little or limited info on this design I personally wouldn't even take chance on it.



    Oh my bad just rambling. LOL
    Last edited by Unbiasedsound; 07-24-2019, 09:32 AM.

    Leave a comment:


  • Kornbread
    replied

    Personal ramblings ...

    " ... various edge-supporting techniques [36], [37]. Both free and simply supported edge options do not present a viable technology for a multiactuator panel frame. The free condition is a free radiating panel with dipole radiation characteristics. However, when observing the typical polar response of a free distributed-mode loudspeaker, a reduction of pressure in the plane of the panel is noticed because of the cancellation effect of acoustic radiation at or near the edges. For that reason the panel is usually placed in a baffle, where radiation caused by the rear part of the panel becomes contained (Pueo, Escolano, Lopez, & Horchens, 2010).

    Zero of my experiments used any kind of baffle and according to this paper they acted as a normal dipole. I agree, sound output 90* to the side was minimal, but isn't less interaction with room boundaries what we desire in a normal listening room? It comes at a cost.

    Their study also used a small rear chamber to absorb the rear wave. In hindsight, I do have several diy sound absorbing panels that would have been ideal for this purpose, hm .....

    "In the technical literature the response of flat panel loudspeakers has been investigated using various edge-supporting techniques [36], [37]. Both free and simply supported edge options do not present a viable technology for a multi-actuator panel frame. The free condition is a free radiating panel with dipole radiation characteristics [and] alternatively, elastic boundaries are a compromise between supported and free edges and can form a viable technology for a multi-actuator panel frame".

    Agreed. The manner in which the panel is supported makes a large overall difference. My panels were blue foam board supported by a wooden frame compromise of 1x2, with the foam panel being lightly sandwiched into place around its entire perimeter with light weather stripping foam. As the panel area next to the frame was cut away, effectively releasing the panel from the frame, the sound 'opened up' and output increased, especially the bass. Eventually, only a few small 'tabs' held the panel in place. Oddly enough, the next panel of treated cardboard sounded best hung from the ceiling, but that experiment was cut short.

    Something along this same area of thought is that there is no mention of stabilizing the exciter (actuator). In personal experiments, there was another large measurable increase in sound output, especially noticeable with music containing bass, when the back of the exciter was glued to a 'spine' effectively anchoring the exciter to the wood frame supporting the panel. The exciters like a solid footing.

    Personally, I feel this is viable technology, especially where space and weight are of concern; car interiors and airplane cockpits first come to mind, and that there is potential, but the complexity of 'getting it right' for the average diy'r is daunting.

    bradley.s and whoever else comes along; continue the experiment, but please measure and report the results for others to grow from.

    Reference

    Pueo, B., Escolano, J., Lopez, J. J., & Horchens, L. (2010). Multiactuator Panels for Wave Field Synthesis: Evolution and Present Developments.  Journal of the Audio Engineering Society,1045-1063. Retrieved from https://www.researchgate.net/publica...t_Developments.

    Leave a comment:


  • Unbiasedsound
    replied
    I said what I had to say in my above post but if you feel there is something in that MAP design worth trying then go for it and let us know your results.

    Leave a comment:


  • bradley.s
    replied
    Single exciter panels are good but they will always generate sound fields that look like image (a). You wind up with hi-fi sound at a limited position. In order to create an array of single exciter panels to perform like (b) you have to shrink the panels down, which degrades low frequencies. MAPs allowed them to create an array with better low frequency response. They attempted to deal with crosstalk in the MAPs through internal dampening.

    We know MAPs work as suitable wave field synthesis arrays based on citation [25], W. van Rooijen, ‘‘Distributed Mode Loudspeakes for Wave Field Synthesis,’’ Master’s thesis, Faculty of Applied Science, Technical University Delft, Delft, The Netherlands (2001). The 2010 paper was concerned with improving MAP performance.

    There's nothing wrong at all with creating a traditional stereo sound field with single exciter panels. MAPs with inexpensive DSP is just the DIYer's next level up.

    Leave a comment:

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