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  • Unbiasedsound
    replied
    Originally posted by Kornbread View Post
    Nice find geosand and bonus points for ease of comprehension.

    This one sentence tells me what I need to know about multiple exciters vs one exciter per panel as NXT is probably the best known contributor to distributed mode loudspeaker technology. They had big plans for its implementation. "This technology, developed by now dissolved company NXT, involved placing surface exciters in positions along a panel that correspond with that panels resonant frequency" (Zielinski, Obiora, & Sansoucy, 2018).

    Ok, these guys read my experiment with the panels. The wood frame holding the panel in with the aid of window seal foam ... where's my name in the reference section?



    Reference

    Zielinski, D., Obiora, O., & Sansoucy, D. (2018, April 25). Development of a Resonant Panel Speaker[PDF]. Worcester Polytechnic Institute.
    These sentences tells me what I need to know about that articles main goals. Which is more about Aesthetics and not hi fidelity sound quality.

    This report covers the development of a walled mounted, low-profile speaker system. A format that
    could be hung from a wall in a way similar to a painting, and the capability to hit low notes. While a small number of speaker manufacturers have created dimensionally impressive
    models, they are almost all very expensive or have limited frequency ranges, leaving a gap in the
    sector for more affordable speakers that can achieve an ideal range.

    You really believe the works he CITED are the only places his knowledge came from?.....I wouldnt doubt for a second that he read this thread or any other thread on any other forum pertaining to DML technology...most wont cite a forum because its not a scientifically based study but credit should be given where its due. If 5 years from now another scientific study on DML's comes out and they mention the Karsonator technique you will all know he got that technique from me. LMAO


    Now like I always ask of those articles is where are there DML panels? Who has heard them? Who has built them? What have they been compared to?

    Leave a comment:


  • Unbiasedsound
    replied
    Originally posted by geosand View Post
    Not sure if this has been posted before.
    An attempt to create a bass DML, 40hz. They are seemingly successful to some degree and it seems to use techniques that have been discussed here before: https://web.wpi.edu/Pubs/E-project/A...er_Stabile.pdf and its relatively easy to read and understand...
    I skimmed through that article and if I am not mistaken they don't use a Spline/brace to hold and stabilize the exciter in place which is a very important factor especially in the lower frequencies at higher excursions where the movement becomes more pistonic then modal it will need something to push off of like a spline or brace.

    Leave a comment:


  • Kornbread
    replied
    Nice find geosand and bonus points for ease of comprehension.

    This one sentence tells me what I need to know about multiple exciters vs one exciter per panel as NXT is probably the best known contributor to distributed mode loudspeaker technology. They had big plans for its implementation. "This technology, developed by now dissolved company NXT, involved placing surface exciters in positions along a panel that correspond with that panels resonant frequency" (Zielinski, Obiora, & Sansoucy, 2018).

    Ok, these guys read my experiment with the panels. The wood frame holding the panel in with the aid of window seal foam ... where's my name in the reference section?



    Reference

    Zielinski, D., Obiora, O., & Sansoucy, D. (2018, April 25). Development of a Resonant Panel Speaker[PDF]. Worcester Polytechnic Institute.

    Leave a comment:


  • geosand
    replied
    Not sure if this has been posted before.
    An attempt to create a bass DML, 40hz. They are seemingly successful to some degree and it seems to use techniques that have been discussed here before: https://web.wpi.edu/Pubs/E-project/A...er_Stabile.pdf and its relatively easy to read and understand...

    Leave a comment:


  • Unbiasedsound
    replied
    Originally posted by bradley.s View Post

    No. Just control over the sound dispersion. Floyd Toole and Earl Geddes use different sound field controls (waveguides in Geddes' case, speaker position in Toole's) to create the illusion of a sound stage. A siren might create an omnidirectional sound field to alert everyone in all directions. The problem most of us deal with in this forum is sound field control in small rooms, our homes. We have to deal with reflections and physically long low frequency waves. Pro audio guys would deal with different problems because they might be in large rooms like auditoriums.

    Imaging and sound stage illusion rely on how you control the sound field.
    So control over the sound dispersion to create a type of sound stage? DML's (no matter how many exciters are used per panel) already have a huge/wide soundstage. DML's from what Ive read already have less room reflections then conventional cone speakers. Are you saying that using multiple exciters per panel will have a wider or better soundstage then using a single exciter? Or are you saying that multiple exciters will have less room reflections then just a single exciter? I cant speak for anyone else but when I want to deal with room reflections I use acoustical treatments like bass traps, diffusers , isolation pads etc etc.

    In the Maps article the only thing I agree about it is using some dampening properties....What I disagree with is that more exciters don't mean less room reflections.




    Last edited by Unbiasedsound; 07-24-2019, 09:26 AM.

    Leave a comment:


  • bradley.s
    replied
    Originally posted by Unbiasedsound View Post
    Sound field? Is that like sound stage?
    No. Just control over the sound dispersion. Floyd Toole and Earl Geddes use different sound field controls (waveguides in Geddes' case, speaker position in Toole's) to create the illusion of a sound stage. A siren might create an omnidirectional sound field to alert everyone in all directions. The problem most of us deal with in this forum is sound field control in small rooms, our homes. We have to deal with reflections and physically long low frequency waves. Pro audio guys would deal with different problems because they might be in large rooms like auditoriums.

    Imaging and sound stage illusion rely on how you control the sound field.

    Leave a comment:


  • RobertOrosco
    replied
    Originally posted by bradley.s View Post

    I'm shooting from the hip on that issue. I'm hoping my low volume level listening requirements will mitigate the majority of the problem. I'm also going to lean heavily on DSP. All the research I've personally seen investigates homogeneous single layers like a single sheet of aluminum or they use foam sandwiched with paper. The panels I'm going to try are hacked together. I have no idea what the internal dampening is on these things. It's a crap shoot. In addition, my geometry is also way off. I'm using very narrow panels relative to typical DMLs. With regard to normal DMLs, mine are a freaking mess.

    What I'm hoping to accomplish is a CBT polar response in the 500hz to 6,000hz frequency range. CBT seems easy to handle below 500hz and hard to do above 6,000hz. If I can get the bulk of the frequencies working I can build a separate DML to handle below 500 and either forget about frequencies above 6,000 or try to figure out an alternative.
    I think everybody had a deal with this problem

    Leave a comment:


  • Unbiasedsound
    replied
    Sound field? Is that like sound stage?

    Leave a comment:


  • bradley.s
    replied
    Twelve actuators per array. The CBT24K has twenty four per array. The goal is a sound field not loudness. It is a sixty inch array so I could meet the 170mm center to center spacing used in the 2010 wave field synthesis paper with nine actuators. I used twelve actuators because it matches Don Keele's transducer ratio in his arrays. Hopefully, a MAP CBT array can be created using fewer actuators.

    Leave a comment:


  • Unbiasedsound
    replied
    Woooaaa that is a lot of exciters for one panel, 24? My Bastat panels that use a single 19mm exciter can fill my 10ft.X12ft. room with adequate spl levels.

    Leave a comment:


  • bradley.s
    replied
    I've been going back and forth on how to support the array. Finally decided on wood railing over aluminum angle. I'm soaking the wood in mineral oil to deaden it a little.

    Leave a comment:


  • Unbiasedsound
    replied
    Originally posted by bradley.s View Post
    Because Don Keele said flat CBTs work and researches said MAP arrays work. That's pretty much the only reason other than DMLs have the characteristics you mentioned.
    How are your CBT panels coming along?

    Leave a comment:


  • bradley.s
    replied
    Because Don Keele said flat CBTs work and researches said MAP arrays work. That's pretty much the only reason other than DMLs have the characteristics you mentioned.

    Leave a comment:


  • Kornbread
    replied
    Mine have a very diffuse kind of sound and nulls to the extreme sides but otherwise a large area in which they sound about the same seated, standing, or to the sides. There is a sweet spot though. I probably missed it, but why cbt with this type transducer?

    Leave a comment:


  • bradley.s
    replied
    Originally posted by Kornbread View Post
    bradley.s You might find this youtube vid interesting. If you are placing multiple exciters on a panel with this many nodes? where do you place the additional exciters so that they act constructively instead of destructively? IIRC, that paper did mention something about the damping of the panel materiel and a minimal separation distance between exciters. If only we had some modeling software ...

    I'm shooting from the hip on that issue. I'm hoping my low volume level listening requirements will mitigate the majority of the problem. I'm also going to lean heavily on DSP. All the research I've personally seen investigates homogeneous single layers like a single sheet of aluminum or they use foam sandwiched with paper. The panels I'm going to try are hacked together. I have no idea what the internal dampening is on these things. It's a crap shoot. In addition, my geometry is also way off. I'm using very narrow panels relative to typical DMLs. With regard to normal DMLs, mine are a freaking mess.

    What I'm hoping to accomplish is a CBT polar response in the 500hz to 6,000hz frequency range. CBT seems easy to handle below 500hz and hard to do above 6,000hz. If I can get the bulk of the frequencies working I can build a separate DML to handle below 500 and either forget about frequencies above 6,000 or try to figure out an alternative.

    Leave a comment:

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