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DIY Flat Panel Speaker Love

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  • rmeinke
    started a topic DIY Flat Panel Speaker Love

    DIY Flat Panel Speaker Love

    Hey fellas,
    How many of you have built a DML panel speaker? Is there any DML panel love out there???

    After reading about the Podium Sound panels and making my way through the expansive AudioCircle thread "NXT.......rubbish??....THINK AGAIN!" (http://www.audiocircle.com/index.php?topic=70541.0) many months ago, I have finally put together some quick test panels to see whether or not these might be an option for the living room were I could set up and tear down the system and carry the light panels away with ease.

    The first panels I put together were small and simple. 1" thick Owens-Corning 2 ft. x 2 ft. Project Panels from Home Depot (http://www.homedepot.com/p/Project-P...-PP1/203553730). The panels are sanded on both sides with a palm sander with 100 grit. Both sides are then treated with a 1:1 mix of PVS white or wood glue and water; this dampens the panel and aids propagation of the sound waves across the panels surface. The exciters are from PE of course, the Dayton Audio DAEX25FHE-4 (http://www.parts-express.com/dayton-...4-ohm--295-224).

    How do they sound? Different. Pleasant. Excellent transients. Percussion and plucked strings are probably the best I've heard. The harmonica sections on Cowboy Junkies "Trinity Sessions" has beautiful dynamic shading that makes for a very realistic presentation. Fast and biting without harshness. Didn't measure the response but think they sound reasonable played full-range. Response likely down to the 100Hz range with a laid back HF response that is quite good and not lacking for my tastes. A 2' x 6' panel is said to get down easily to 50-60Hz. Compared to my Tang Band W4-1879 in OB, they are noticeably more sensitivity; 91+dB range.

    As I said... different sounding. You have to get adjusted to the presentation as the panels are distant sounding after switching from my open baffles. There is a lack of presence and a sensation that the music is emanating from behind the speaker, through the panel, then to the listening space. Once adjusted they are VERY ENJOYABLE and NATURAL sounding. I listened to Muddy Waters "Folk Singer" (on gold disk) and Cowboy Junkies "Trinity Sessions" into the wee hours of the night a few nights ago just enjoying the dynamics and naturalness. Very nice indeed. All from $30 worth of parts and 1 hours time. Amazing honestly. Would be interesting to combine with an open baffle bass panel. Lots of different configurations.

    [edited Jan 4 - The panels have opened after the exciters have fully broken in and the panel treatment has cured (harder panel skin). The small panels are fast, detailed and considerably more clear than the time of the initial post.]

    Curious to hear what others have built and their listening impressions. Anyone enjoying DML panels in their system at the moment?
    Last edited by rmeinke; 07-10-2015, 01:01 AM.

  • Unbiasedsound
    replied
    Originally posted by bradley.s View Post
    Your explanation was good enough for building single exciter stereo DIY speakers. But the Tectonics guy is building speakers used in professional installations so he needs to be accurate. You should probably watch his videos so you can get ideas on how to improve your speakers.
    SIGH!!!!!!!! I have watched ALL those tectonic videos before multiple times awhile back. Since you are building a design using multiple exciters you should watch those videos to improve on your design.

    Leave a comment:


  • bradley.s
    replied
    Your explanation was good enough for building single exciter stereo DIY speakers. But the Tectonics guy is building speakers used in professional installations so he needs to be accurate. You should probably watch his videos so you can get ideas on how to improve your speakers.

    Leave a comment:


  • Unbiasedsound
    replied
    Originally posted by bradley.s View Post
    That video technically supports what I said SMDH....DML's have a very diffused sound the echo reflections are less prominent then with conventional cone speakers therefore the reflections are less directional.

    This is one of the reasons DML's have very little to no microphone feedback.

    Leave a comment:


  • bradley.s
    replied
    Originally posted by Unbiasedsound View Post
    DML's from what Ive read already have less room reflections then conventional cone speakers.
    No. This is how it works.

    https://www.youtube.com/watch?v=tWZdPkH9IgA

    Leave a comment:


  • 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.

    If I want to control the dispersion of my panels and or control the reflections directly from my panels I have already given many techniques to do so. One of the techniques I have said so many times is putting a small piece of damping material directly on the back of the exciter (without a spline) and or directly on the spline. This technique reduces reflections and changes the tone so they sound more accurate and less diffused. The more dampening you use the less reflection but there are side effects to too much damping like less treble so the amount of damping needs to be just right. I learned this technique from Dr.Shelly Katz who worked on the newer Podiums in which he utilized this technique. I also use a technique (which I was reluctant to give out lol) similar to WAVE GUIDES on my frames of my panel in which I took from the DIY Karlsonator speakers because the shape of the frame can control the dispersion of the panels sound field. My frames are 4 inches length so even the frame itself acts like a wave guide and using the Karlsonator technique can help shape and control the sound field dispersion.

    I think I better stop posting as I am giving out too much of my techniques. LMAO



    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:

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