DML Flat Panel

DML Flat Panel


Designer:
Rich Meinke

Project Category:
Freestyle

Project Level:
Beginner

Project Time:
1-2 Hours

Project Cost:
$50-$100

Project Description:
This project, the first in the set of DML Flat Panel “Beginner Series” projects, will briefly introduce you to DML speaker technology and explain, step by step, how to build a simple 2’x2’ DML flat panel speaker from materials that are readily available.  In short, this project is the quickest way to get listening to a nice sounding flat panel speaker.

Design Goals:
WHAT IS A DISTRIBUTED LOUDSPEAKER (DML)

A Distributed Mode Loudspeaker operates on completely different principals than conventional dynamic/cone speakers or other panel speakers such as electrostatic or ribbons.  Unlike those types of transducers where the diagrams move in a pistonic motion, a DML flat panel speaker randomly generates vibrating nodes producing output at different frequencies and amplitudes across the entire panel with equal output from both sides of the panel.

This provides some very interesting advantages:

  • Near Omni-directional dispersion pattern, radiating equally from the front and back of the panel, has little narrowing of off-axis output with increasing frequency.
  • A single diaphragm (panel) capable of producing a true full-range response.
  • Low 3rd order distortion provides excellent voice intelligibility.
  • Panels and the resulting finished loudspeaker are thin and light-weight, making them easy to move around the listening room or put away out of sight.

Large, tall panels operate as a line-array which exhibit a 3dB loss in sound pressure compared to a point source that decreases by 6dB for every doubling of distance.  Not a DML technology advantage however, even a 24” x 36” panel will display qualities of a line-array at reasonable listening distances.  Some explain an array sounding like a large set of headphones. To me, listening in the focused array is like stepping into the recording venue.

LISTENING TO A DML PANEL

The term “magic” has been associated with these flat panels long before I began building and listening to my own panels.  After listening to them for some time now I can only agree that there is, indeed, magic in these panels!

The near Omni-directional output is an absolute joy to listen to.  They throw a huge soundscape that just fills the room.  Even tiny 14.5” x 12” panels absolutely fill the room with delicious flat panel sound.  If you didn’t know that the tiny panels were speakers you would have little clue where the music is emanating from.  This is very unique.

The panels are also very light and the large surface area requires little movement to generate sound pressure.  This leads to a “fast” and detailed speaker.  Even on recordings that I know very well, I began hearing nuances in recordings that I had not heard before.  The detail that these panels are able to extract is not etched or harsh and provides the detail in a polite way; much different than what we are accustomed to with conventional high quality speakers.

DML’s are sensitive and require little power to play loudly.  For instance, a single Dayton Audio DAEX25FHE-4 exciter on a 2’x2’ XPS panel is roughly 91+dB.  DML panels also do not suffer from Baffle Diffraction Loss so a 91dB panel is equivalent to a 97dB traditional box speaker, assuming 6dB diffraction lose.  While this is a very compelling quality, panels will saturate often times before the thermal limits of the exciter are reached.  This reduces the output of the panel.  This is not to say that even a small 2’x2’ panel cannot play to satisfying listening levels.  Where higher output may be required, a multi-panel array is a solid solution. Look for updates in the Flat Panels section of the Speaker Projects area of the Parts Express Project Gallery for a DML multi panel array design.

It is my opinion that these flat panels are not as well suited for rock or synthesized music, but best with: Jazz, Blues, vocal and other acoustic music genres.  Well recorded, live performances on these panels are fantastic and bring the performers into the listening room like no other speaker I have had the pleasure of listening to over the last 30+ years.

Finally, a word of caution from my own experiences listening to these panels.  The presentation of a DML is different as sound is produced across the entire panel; this makes for a more diffused output compared to a traditional speaker.  There is a lack of presence and a sensation that the sound is coming from the back of the speaker, through the panel, then finally to the listening position.  This took many hours of listening to adjust to.  I had nearly given up on these panels before giving them a few long listening sessions.  Also, after switching from my KEF Q500s to the panels, I heard a constant underlying, vibrating signature with my XPS panels.  While it is a warm sound, it is an aspect of the panels that I had not noted previously.  I adjusted to this aspect quickly and the KEF remains in storage and has not been connected to my audio system for some time now.

These speakers may not be for everyone due to music tastes and personal preferences.  But they are easy to build, inexpensive, and take only an hour or 2 to put together so I can highly recommend them to anyone looking to build a musical sounding speaker.  I always wanted to own an exotic flat panel speaker, and these have exceeded my expectations.

Driver Selection:
Based on sound quality, the most recommended exciter for small, light-weight panels (as used in the project) is the Dayton Audio DAEX32U-4 Ultra.  The DAEX32EP-4 Thruster is a close second, and for an inexpensive exciter that still performs very well, I can recommend the Dayton Audio DAEX25FHE-4.

Enclosure Design:
For the easiest build, use 2’x2’ Project Panels from Home Depot (Owens Corning FOAMULAR® 150 rigid XPS foam insulation).  These are cheap, require no cutting, and will give you a good introduction to DML panel sound.  However for better performance, a panel 24”x32.5” (golden ration) would provide better low and high frequency response.  Home Depot will usually, but not always, cut a 4’x8’ sheet of XPS on their panel saw.  If this is possible, go for the larger panels and follow the same process outlined below.

Enclosure Assembly:
Building the panel is simple and can be completed in 1-2 hours.  It is important to sand off all of the panel “skin”.  The sanded surface should be dull, soft and velvety feeling, with none of the original sheen still present.  After the panel is prepared, it must be treated with a mixture of even parts of glue (wood or white) and water.  XPS, non-treated, does not sound as good and has a “plastic” sound quality.

Step 1 – Panel preparation.

  • Round the corners of the XPS project panel. Using a glass or bowl as a guide, lightly mark the panel using a pen or pencil.  With a serrated knife, cut up to 1/4” from the marked line.  In other words, leave extra material by not cutting right up to the marked line.  XPS tends to break away in large chunks and could ruin our nice round corner.
  • To finish rounding the corner, use an electric palm sander and 100-grit sandpaper by sanding right up to the marked lines. Sanding goes quickly, so use light pressure.
  • Again with 100-grit sandpaper, sand off the XPS panel’s “skin” by holding the sander firmly but applying light pressure, make straight passes over the panel in the same direction with each pass. Clean the XPS dust off the panel and sandpaper frequently to avoid build up that leaves scratches to the panel.  Sand both the front and the back of each panel until there is no “sheen” on the panel’s surface.  Better to take off more panel than leave any skin.
  • Break the edges and corners of the panel by taking light pressure with the sander held at a 45 degree angle to the edge. Be careful to not apply too much pressure as it can create gouges.
  • Once you have reasonably round edges, finish the panel by hand sanding the edges and corners. With 100-grit sandpaper, use light, long passes over the entire length of the panel’s edge.  While not required, finish off with 150-220 grit if you have it handy.

Step 2 – Panel treatment.

  • The panels need to be treated with even amounts of water and wood or white glue. If you want to color the panels black, mix black ink with the water but keep the 1:1 proportions if not extra glue.  You can mix the glue, water and ink (if desired) in a flat bottom glass bowl.
  • With a 2 Inch foam roller, roll on the water and glue mixture over the panel. The mixture is thin so don’t worry about applying too much but make sure it is even.  Treat 1 side for each panel.
  • If you are not coloring the panels with ink, do not treat the round edges. If you are coloring the panels, use only 1 thin coat on the edges.
  • Repeat the treatment on the other side until both sides of the panel are treated twice. To make this process go faster, use a hair drier to quickly dry the treated panel.

Step 3 – Apply the exciters to the panel.

  • Each exciter is mounted roughly 2/5 from the top and side of the panel. On a 2’x2’ panel, place the exciter 9 ½ inches from the inside and 10 inches from the top.  I mark this location by making a light indent with a pen or pencil.  Mark both panels but make the pair in a mirror image.  I position the exciter so that the wire connection tabs are facing the inside of the panel.  So imagining viewing the panels from the listening position, the exciters will be mounted at the top inside of each panel with the tabs pointing to the inside of the panels.
  • Lightly sand the location where the exciter is to be placed. Blow or brush off any dust so the exciter will make a good bond to the panel.
  • Place the exciter on the panel in the marked position. The exciters come with 3M VHB (Very High Bond) adhesive pre-applied to the exciter.  Just remove the paper exposing the adhesive and slowly lower the exciter on the panel surface.  Press the exciter with light pressure.  For best results, glue the exciter to the panel with the same glue you use for the panel treatment.  I would try the VBS first to allow you to try another panel size or material.

Tips & Tricks:

Equalizing
As stated earlier, light weight flat panel made with XPS have an uneven frequency response.  One of the biggest improvements that you can make to these panels are equalizing and shaping the response to your preference.

2 areas that benefit:

  • Smoothing and tailoring the overall frequency response to your liking.
  • Extending the bass and high-frequency extremes as desired.

I have used the Behringer DCX2496 Loudspeaker Management System & Crossover for many years with my open baffle speakers and appreciate the power and flexibility.  I no longer purchase expensive passive components and use this for all cross-over and equalization duties.

Extending bass response and adding “slam”
While these particular panels can sound quite good down to a reasonable 80Hz (can go much lower on larger panels), flat panels of all types have a general reputation for bass that lacks “slam”.  These panels are very open, “fast” and clean sounding and had concerns about the potential of adding bloat or muddy bass response with a subwoofer.  But in an attempt to add slam, I tried a small (and hopefully more agile) 8” sub, the Dayton Audio SUB-800, and am very happy with the results obtained with this small sealed sub, especially considering the low cost.  Playing these at reasonable levels the quality is very good; reading the user reviews on the PE website confirms my own results.  They also look really nice and not what you would expect from a subwoofer costing under $100 – very highly recommended!

To relieve the panels from playing lower bass, I recommend the Harrison Labs FMOD Inline Crossovers if you have no other means of preventing the panels from playing the low frequencies.  For smaller panel as described above, I recommend the 150Hz crossovers (the specific model is listed below).  For larger panels, the 100Hz crossover would likely be a better choice.

If you need higher output and greater extension, the Dayton Reference or Ultimax based subwoofers with high powered plate amps will obviously provide significantly better performance.

Measuring speakers
To give insight and guide equalization, I recommend some means of measuring the speaker response.  Keeping with a low cost approach, I have used the following with my iPhone to good effect:

  • Dayton Audio iMM-6 Calibrated Measurement Microphone
  • Audio Tools iPhone app (base app with no in app purchases) to apply the calibration file of the iMM-6 mic.
  • Audio RTA is an inexpensive RTA app with 1/12th octave resolution.

While I own Omnimic and REW measurement systems but still use this combination above often as it is so quick and easy to use; very handy.

Conclusion:
There is something special about these flat panel speakers that make them very enjoyable and just plain fun to listen too.  I’ve gone back and forth between my DIY open baffle speakers and KEF Q500s but I keep coming back to these flat panels despite the drawbacks mentioned above; all of this from a speaker that costs about $50.  If you enjoy listening to music instead of a pair of speakers, you cannot go wrong with these magic panels!

About the Designer:
Rich is a member of the Parts Express Speaker Building Team.

Projects Part List:

295-235 DAEX32U-4 Ultra 32mm 40W 4 Ohm 2
300-627 Dayton Audio SUB-800 8″ 80 Watt Powered Subwoofer – [optional] 1
266-276 Harrison Labs FMOD Inline Crossover Pair 150 Hz High Pass RCA – [optional] 1
100-020 Wired Home SKRL-14-50 14 AWG OFC Speaker Wire 50 ft – [optional]. 1
Project Panels 2 ft. x 2 ft. Project Panel-PP1 2
Wood or White “School” Glue 4oz 1
Foam paint roller 1
1-2 oz. Black ink 1

32 Comments

Add yours
  1. 4
    Wmg

    If the 8″ subwoofer mentioned in this article is used why would you need those RCA crossovers if Using low-level input and high level outputs to the panel speakers?

    • 5
      Rich

      Hello Wmg,
      When using the Dayton sub, I do not use the high-level outputs. Reviewing the manual, it appears that there is no high-pass filter: “Note: High level outputs are paralleled to the high level inputs with no high pass filter”. So the line-level Harrison Labs crossovers are required. I used the 150Hz high-pass as I had it on hand, but I would want to try the 100Hz filter to allow more flexibility in positioning the sub-woofer. With the higher 150Hz crossover point, the sub needs to be positioned close to the panel.

      I’m still impressed with the Dayton sub for music played at reasonable levels. The value is high and perfect for an inexpensive audio system. For higher output I would not hesitate purchasing the larger 10″ and 12″ as the reviews, like the 8″, are very positive and seem to have the same characteristics; tight and musical.

      Apologies for just responding to everyone. Just saw these comments.

  2. 6
    Robb

    Wicked cool Rich.
    Curious, if space were no object and these could be suspended, would a 4′ x 4′ project panel result in louder and fuller sound? I’m looking for a solution in which the walls of a room appear to be talking.

    • 7
      Rich

      Hi Robb,
      Absolutely, a larger panel would be excellent. Surprisingly, I found larger panels to have better high-frequency response using the same exciter and foam panel. Large free-mounted panels had drum resonances that I was not able to remove, so a more firm suspension would be recommended. You would also need material to absorb the panels rear radiation.

      Register on the PE TechTalk forum to talk over the design you have in mind. This is a VERY INTERESTING implementation!

      • 8
        Robb

        Thanks for the tips. I’m thinking about framing these with thin strips of furring, both for durability in transport
        and for looks. Do you think this will increase dampening of output? But perhaps temper some of the resonances you mentioned?
        Thanks much!

    • 10
      Rich

      Hello David,
      On smaller panels, I prefer light suspension as there is more “air” and detail in my opinion. Generally, I would say that opt for the least amount of suspension but a panel free of resonance/panel noise. For most panels, I place 2 small pencil erasers under a thick, soft, tri-folded piece of fabric so that the panel is really only touching the fabric where the erasers are (a few inches into the panel where the large round corners begin). On the top, I prefer to rest the top of the panel on large rubber bands toward the top corners. For all but one exciter, this has controlled panel resonances yet still delicate and airy sounding. Again, as little suspension as possible and only enough to control resonances.

      For the single exciter that this suspension did not work as well, I had to rest the top of the panel against the wood frame support that runs the full width of the panel. The top wood support piece is then covered with the same thick, soft fabric used for the bottom “suspension”. This was needed to control the higher levels of panel noise that the 24 watt high efficiency exciter placed onto the panel.

      But, to be honest, there are MANY different methods and materials that could work to control resonance. So would a viscose elastic material work? I don’t see why not. Experimenting with different materials is half the fun.

      Build on David!!

  3. 11
    Paul Thompson

    I absolutely love mine (especially used in conjunction with a pair of very fast 15 inch single driver speakers [and two 12 inch subwoofers!!]. By themselves, they defintely have an uncanny, magical midrange and treble, in terms of presence, harmonics, decay, soundstage, etc., that I doubt you can achieve without some form of DML.

    I wish we knew more about the various effects of different mounting/placement strategies, materials, etc., but for now I couldn’t be happier. Every singel person who’s heard them was pretty much stunned to silence by what could be achieved with an exciter and piece of foam board.

    I’d love to make a larger panel but it seems to 4×8 sheets of this material are much thinner. Is that the case, I just don’t know what to use.

    Also, on your panels it looks like you have some kind of material around their edges. If so, what’s that all about?

    Anyway, I must say that this is one of the most startling stereo projects I’ve ever heard of. Always wanted to hear this technology and I certainly was not disappointed!

    Thanks again so much.

    • 12
      Rich

      Hello Paul, glad to hear you are enjoying your magic panels! They really are unlike any other speaker I have listened to and it seems you may feel the same. Certainly not the perfect transducer, but to me, they sound the closest to “real”, live music.

      I would like to work with you on building a larger pair of flat panels. I would join us on the PE TechTalk forum; you can reach me there. If you don’t want to post to the forum, you can exchange email addresses and go from there!

    • 14
      Rich

      Hey Jim, I have been using mainly 1″ XPS but also 3/4″ on small panels. After trying even low grade EPS, I would build more 3/4″ XPS panels; even those in the 24″x32″ size range as I feel the 1″ XPS is over-damped.

      If you can purchase a quality EPS foam panel, I would try that over XPS. Don’t get me wrong, I really enjoy XPS but feel the lighter and more resilient EPS *may* be a better panel material.

      The low quality I’ve used is 3/4″ but closer to 5/8″. It has more panel noise XPS and, as a result, does not play as loud before panel noise becomes an issue. 1″ thick low grade EPS may fare better in this regard.

  4. 15
    JJ

    Just saw that your #1 pick for the exciter is out of stock and won’t be in until June! Do you know of another exciter that matches this one? I know in your write-up you mention your second pick is a “close” second. What exciter should a guy use without sacrificing any SQ if he cannot wait until June?? Thanks!

  5. 16
    Rich

    Hey JJ, the Dayton Audio DAEX32EP-4 Thruster is also a very nice sounding exciter and works on a wide variety of panel materials. They are also on sale at the moment. Whats not to like!!

    Let us know how your build goes!

    • 17
      JJ

      Okay, so we went ahead and did a quick build with the cheapest exciter you mentioned in your write up. Well, they sound really good. Exactly as you say…good…interesting…different. Can’t stop listening to them. A little bass shy. Question – is one of the improvements in moving to the Ultra exciter improved bass performance? Thanks! Now, back to listening…

      • 18
        Rich

        YES jj !!! Glad your enjoying the panels. The Ultra’s will not go any deeper honestly; only a larger panel will provide deeper bass. I prefer pairing the panels with a subwoofer for better extension and *slam*. The Dayton Audio SUB-800 has worked very well for music at reasonable output levels. I would not hesitate trying one of the larger Dayton subs.

        For me, the Ultra’s provided more detail… they are quieter with less panel noise. This, to me, is the reason for the improved detail. This improved detail comes, unfortunately, at the expense of a more rolled-off high frequency response due to the larger voice coil.

        Preferences. I still prefer the Ultra but I do really like the DAEX25FHE-4 as well. Exciters are pretty inexpensive so fun to try different ones. :-)

  6. 19
    Mark

    Looks interesting…. A couple detail questions … 1) It appears in the photos that you’ve eased all edges, front/back, but, less than half-round ? 2) What is the diameter of the “bowl” you used to draft the corners ? Different radius for different sized/ratio panels ? 3) In the forums there’s discussion about driver placement offsets… Is the “Understanding and Using Exciters” pamphlet information best practice? Thank you for your time.

    • 20
      Rich

      Hello Mark,
      I usually use a 1/2″ router bit to round the corners however for this particular panel, I used less of the bit and did not perfectly round the edges as I normally would as I wanted to try felt to help more smoothly terminate the panel edges and a more finished look. I was not as happy with the exciter initially used with the panel so I can not say whether the felt edge treatment was advantageous or not.

      The bowl I used was about 8 inches in diameter.

      For offsets, I normally follow the PE’s “Understanding and Using Exciters” 2/5 placement. For these square panels (not optimal), I moved the exciter up 1 inch to avoid equal dimension between the panels bottom and edge. This is a greater ratio than the “Monacor placement” where the exciter 1 position would be located at 4/9 X and 3/7 Y. Using this ratio, the exciter would be moved roughly 1/4″ off center for a 24″ x 24″ panel. Again, a smaller offset than the 1″ I used but the differences in the real world are very small between all 3 exciter locations I mentioned.

      • 21
        JJ

        So, if you had to say what is the “best of the best” that you have tried so far, what would it be? Would the Ultra in the larger “Golden Ratio” panel be the best you have heard? One other question, is there much of a difference in sound between the 12″x14.5″ panels and the 2’x2’s? Thanks for enduring endless questions!

        • 22
          Rich

          Hey jj, no worries about the questions… keep them coming.

          You really can not make a claim as to which exciter is “Best” honestly. So much depends on panel material, how the panel is suspended or just the overall design and what you, the builder, is attempting to achieve (small panel integrated with a sub, full-range panel w/no EQ, etc.). Personal preferences also play a huge part as well. For instance, I listen to mainly listen to acoustic music so I am perfectly content listening to a higher powered/larger diameter vc exciter where are some prefer the better extension of a smaller exciter. Much to consider.

          I really like the sound of the smaller panels. They seem cleaner and more clarity with less panel resonances as the signal leaves the panel more quickly.

          The one thing I really like about about these DIY panels are that they are inexpensive and easy to build making it much more feasible to try a number of builds with different exciters. Its just plain fun!

  7. 23
    Max Wagy

    Yes, flat panel transducers can be mesmerizing… which is why I finally succumbed and called those people up in White Bear Lake, Minnesota. Their website, by the way, has some wonderful articles concerning placement and mounting and semi-hand manufacturing, since that’s how they do it. magnepan.com

  8. 24
    Aaron Benavides

    I’ve been wanting to create these on a larger scale for some installations for a while! I’ve made some smaller ones and loved them. a am thinking of essentially making free standing partition walls or “hollywood” flats and putting the panel on those about 5’x8′. I also have a few ideas about bring some bigger bass into the picture.

    I’d love to talk some more about this stuff and maybe work with other like-minded people to find the way to get the best sound out of these. how can I find you on the forum?

  9. 25
    Justin

    I have ordered 4 of the DEAX 32-4 thrusters, simply because I want to play with this flat panel concept. I am going to set them up in my office as a conversation starter. My amp is only 8 ohm stable so I plan to wire these in series. With four exciters that gives me a lot of options. What are the pros and cons of 4 smaller panels vs 2 larger ones? I am even considering placing all 4 exciters on an entire 4’x8′ sheet. :) I like the idea of an entire “wall” of music. I plan to hang these from the drop ceiling on my office (I am thinking rubber grommets in the “top” corners and suspending them from a wire) as I have few mounting options without drilling into concrete block. Any advice on hanging them and how that will impact the sound? I am also considering hanging these so they fire downward, a “ceiling” of sound.

  10. 26
    Don

    Hi i have been looking for speakers to build for my new diy 6bq5 se stereo tub amp it will be only 5 watt per channel
    what do you all think if these speakers will work with 5 watts?

    • 27
      Frank

      Don,
      I think your 5 watt tube amp would do great. I found the exciters take awhile to break in and really sound good. 20+ hrs. I use the Dayton DTA 1 and Lepai both 15w plenty.

  11. 28
    POL

    Hi, I am a long time lover of DML louspeakers, I have built many models from strong carton to wood and so on, and I wont ever return to classic loudspeakers. My best choice is “carton honeycomb”
    this said, you type “a sensation that the sound is coming from the back of the speaker, through the panel,”
    Right! and the solution is very easy: listen from the other side…. LOL… no joke, you wil get a better hi-range…

  12. 29
    Ian

    have you listened to commercial models of DML speakers? I have a pair of TEAC / NXT speakers and a LOGITECH mm-28. Suprisingly, the smaller all-in-one mm-28 sounds better than the larger TEAC panels. I suspect the secret to getting the best sound out of exciters is panel material, placement of exciters and panel surround material. The commercial manufacturers have access to design software that is not avaliable to unlicensed DIYers like us. My plan is to use either of these models as midrange/fullrange? plus a large open-baffle (probably H-frame ) bass driver crossed over at between 100-250Hz. . I believe this will provide the best performance from DML technology without excessively large panels. Have you experimented with this type of FAST system?

  13. 30
    Frank

    At first I didnt want to believe this could work. It just defies common sense. The build out was easy, thanks to Rich and PE.
    The sound? As mentioned previously, it places the performance in your living space. What surprised me was walking in and around the room, the sound seems to radiate and small panels fill a large room.
    I settled on carton-honeycomb-standard shipping boxes at Office Depot. Treated both sides with a spray shellac. It gives the panel strength. Follow the 2/5 rule for driver placement, I settled on a size of 17x.5 by 18″. I tried the XPS material, but found the carton superior.
    Whereas the XPS placed the sound more from behind the panel-the carton placed the sound at the panel-was more transparent…in other words, the material is critical as is the insulation supporting the panel. I didnt find it necessary to round the corners, keeping them square.
    My frame is similiar to Rich’es design, raised the panel off the floor about 13-14″.
    Regarding amplifiers, found the Dayton DTA 1 pure magic with the panels.

  14. 31
    Damon Palyka

    great tutorial, thanks!
    I am looking to get some expanded low end range from something like this (musical not effect) in the 15-40hz range and the 10-20khz range, I bought the DAEX25X4-4, any ideas on implementation?

  15. 32
    Matthias

    I’m interested in building the shipping box material with shellac. Is it just corrugated cardboard box material? Or, is it the special honeycomb cardboard they use for architectural scale model building? Should the shellac be applied to the small area that the driver will mount to? I have seen comments that care should be taken when installing the exciter. Anyone have any specific instructions?

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