With respect to full range DMLs, absolutely,
I have a narrower interest.
I want these particular panels as home theater center channels, principally dedicated to the reproduction of human voices because I dream about watching and listening to films without needing to read subtitles.
Of all instruments, generally cellos most closely correspond to the range, timbre, and overtones of human voices.
Cello sound boards typically use spruce with oil or spirit based varnish.
Lots of difference between a cello and a DML, but it seems like a reasonable thing to try.
I appreciate you posted this some 4 years ago, I hoped you stand me a question or two.
If I follow you, one could coat the back and front of such a panel with resin or epoxy or maybe even something like lacquer or shellac or pva.
Have you tried this?
Does anyone else have suggestions for what to use?
Steve,
I saw this post from 2020 and wondered if you have any more memory of what you used and how you constructed it?
Aluminum?
Using the spray adhesive did you use it like contact adhesive (it works well for this), e.g., spray both surface, let dry, then assemble?
Still looking for and playing with possible panel options for my center channel DMLs. Max size around 16" x 6".
Treasures in this forum. Many thanks.
aagas.
I can only remember that it was a 3M spray mount.
I think you only sprayed one surface?
Total thickness was about 1mm I believe.
Not getting air bubbles was a pain.
I posted some time ago about using two of my card panels as left and right channels in my surround sound system with no centre channel.
I even made a recording of Big Ben.
They were made with the same methods of gluing two thin cards together with neat pva.
I mentioned how they transformed the listening experience similar to replacing an old tube TV with a ultra high quality flat screen.
I mentioned that in one close up scene where two lovers were standing in the middle of a road staring into each others eyes , when I noticed that instead of background music of a cello, there was according to what I could hear, was a person sitting on a chair next to them just out of shot, actually playing a collo !
It was so realistic.
I played this scene over and over again, I thought it was so funny 😁
I would have left them there permanently but my dog would have eventually destroyed them.
Steve.
I can only remember that it was a 3M spray mount.
I think you only sprayed one surface?
Total thickness was about 1mm I believe.
Not getting air bubbles was a pain.
I posted some time ago about using two of my card panels as left and right channels in my surround sound system with no centre channel.
I even made a recording of Big Ben.
They were made with the same methods of gluing two thin cards together with neat pva.
I mentioned how they transformed the listening experience similar to replacing an old tube TV with a ultra high quality flat screen.
I mentioned that in one close up scene where two lovers were standing in the middle of a road staring into each others eyes , when I noticed that instead of background music of a cello, there was according to what I could hear, was a person sitting on a chair next to them just out of shot, actually playing a collo !
It was so realistic.
I played this scene over and over again, I thought it was so funny 😁
I would have left them there permanently but my dog would have eventually destroyed them.
Steve.
What kind of cards did you use?
Size?
Exciter?
Did you paint the surface of the cards with pas too?
This sound like just what I need ;-)
Last edited:
Follow up...
spedge said:
The great art supply store down the street from me has Rising Museum Boards made of 100% cotton fiber.
2 ply boards equivalent to approximately 500 gsm (grams per square meter) or 185 lb cover weight.
Widely used in archival framing, matting, and preservation of fine art and documents due to their high quality and archival properties - acid-free, lignin-free, and buffered with calcium carbonate to protect against environmental factors
They have them in different thicknesses:
Gluing two 2-ply with pva would give me approximately 1.5 mm.
I'll drive them with Thrusters so I have plenty of power.
Thoughts appreciated.
spedge said:
Steve - I did mean pva rather than pas.
The great art supply store down the street from me has Rising Museum Boards made of 100% cotton fiber.
2 ply boards equivalent to approximately 500 gsm (grams per square meter) or 185 lb cover weight.
Widely used in archival framing, matting, and preservation of fine art and documents due to their high quality and archival properties - acid-free, lignin-free, and buffered with calcium carbonate to protect against environmental factors
They have them in different thicknesses:
- 1-ply: 15 pt 0.015" | 0.375 mm
- 2-ply 30 pt 0.030" | 0.75 mm
- 4-ply 60 pt 0.060" | 1.50 mm
http://www.legionpaperforum.com/ask-an-expert/post/1932875
Gluing two 2-ply with pva would give me approximately 1.5 mm.
I'll drive them with Thrusters so I have plenty of power.
Thoughts appreciated.
Last edited:
I just used card from cereal boxes.
And glued the two printed surfaces together.
I used diluted pva to coat the outer surface and scissors to cut the panel Shape.
Very simple really.
On later version I made a dome for the centre similar to the veneer version in the youtube video.
I also used weights to improve the lower midrange.
Steve.
And glued the two printed surfaces together.
I used diluted pva to coat the outer surface and scissors to cut the panel Shape.
Very simple really.
On later version I made a dome for the centre similar to the veneer version in the youtube video.
I also used weights to improve the lower midrange.
Steve.
The first demonstration that I saw of this concept was some years ago at a coffee shop. A friend of mine had one of the blue tooth exciters that, when held to the window of the coffee shop, left me slack jawed. I wasn't expecting much, but for what I heard, it just didn't gel in my mind. Even though this has left a lasting impression on me, I have yet to experiment with the idea. I have to admit though, if the idea of using say a violin or cello has much merit, that would be a very cool starting point. Great subject and thread guys. Much appreciated.
thanks for the heads up. Since I have the plaster I will give it try to see but my main plan was to use it for the 50/50 wash to stiffen it a up a bit. I had also thought about a coloured top coat (light coating) just for looks. will keep you posted don't hold your breath it will be a while yet. Thanks so much for your feedback.
Regarding the separation of the main components of the exciter, namely the voice coil and the magnet(s), do have a look at this link. I don’t visit here often, as life tends to be rather busy. However, I’m determined to make this happen one day. I’ve experimented a bit with untreated 10mm polystyrene, approximately 2mm thin wood (not plywood), and some plastic-like sheets. It’s far superior to simply attaching an exciter to them, which tends to be rather heavy. The flattened coil is virtually weightless, allowing the heavy magnet(s) to be positioned away from the flat panel without adding any extra weight. I don’t have much in the way of photos to share just yet, but the concept is straightforward enough for anyone to grasp. I hope someone here will give it a go!
The coil is flattened by applying pressure from left to right, leaving a slight gap between the two sides. Two rectangular neodymium magnets used, although I’m not certain of their strength. The concept was inspired by a discussion found somewhere in the middle of this thread. The top and bottom sections of the flattened coil were not covered by the magnets; only the vertical area of the coils was utilised. I can’t quite explain why this is necessary or not, though. Most likely, one could use a round coil, flattened as it is, along with a round magnet that can be found inside the exciter itself or from another speaker. I haven't tried that yet.
The coil is flattened by applying pressure from left to right, leaving a slight gap between the two sides. Two rectangular neodymium magnets used, although I’m not certain of their strength. The concept was inspired by a discussion found somewhere in the middle of this thread. The top and bottom sections of the flattened coil were not covered by the magnets; only the vertical area of the coils was utilised. I can’t quite explain why this is necessary or not, though. Most likely, one could use a round coil, flattened as it is, along with a round magnet that can be found inside the exciter itself or from another speaker. I haven't tried that yet.
Last edited:
Moray, I fear you'll be disappointed. Plaster is fairly gritty, and shrinks. I've used it in paint in the past, and it didn't work. Talc is the go, but by all means test it out, it's how we learn, and you may have a different result to me
Eucy
I have already purchased a packet of plaster so will at least give it a try. I can pick up some talc along with some graphite powder when I get back home to Calgary and compare them all and see what they look like. Thanks for your interest and suggestion.
Alvipet (Sheet Control), whom I've not seen on the forum for a long time - he had shared some geometry on how to select optimal exciter location, also multiple exciters. I couldn't find it with a search - maybe it was a link to somewhere else, that someone else provided? I remember a diagonal line on the lower right side of a diagram of the DML membrane, with the math and x's marking the exciter locations. Can anyone please direct me to it? Thanks!
Thanks so much Homeswinghome! Your talent for documenting and organizing infomation has been fantastic for this thread!
Has anyone seen or tried this from Parts Express?
Looks like a baby DML.
Dayton Audio DML25-4 2" Distributed Mode Loudspeaker Transducer 20W 4 Ohm
Looks like a baby DML.
Dayton Audio DML25-4 2" Distributed Mode Loudspeaker Transducer 20W 4 Ohm
I believe I mentioned in my earlier post that I drew inspiration from that thread. The link below.
The entire discussion revolved around the creation of Rubanoid, while Joppe Peelen had taken that concept and applied it to make a flat panel function as a Distributed Mode Loudspeaker (DML). He utilised a flattened coil, or more likely a flat coil of his own design, to generate the pistonic motion that, allegedly, the stiffer plywood would not permit. If you’ve seen his videos from a few years back, you’ll notice that the flat panels he employed exhibit that pistonic movement, sometimes rather vigorously. In any case, member sergiu2009 completed his Rubanoid a few years ago, and the thread eventually lost momentum.
The idea I’m discussing is somewhat different. It involves adhering the flattened voice coil directly onto the flat panel on the same surface, rather than at a right angle. Additionally, the magnet(s) would be positioned slightly apart from the panel and secured to the frame behind it. If glued properly, the coil wouldn’t be able to move, but it would exert considerable effort to do so. This rigidly fixed coil would transfer the surface sound waves to the flat panel, effectively transforming it into a DML. A key advantage of this approach is that a commercially available exciter wouldn’t add unnecessary weight to the panel.
Here’s a link to a video demonstrating how a flat piece of paper can produce music. It’s essentially the same concept, one way or another.
The goal is to make a flat panel act as a DML, but using an exciter to achieve this is akin to cutting the cone off a standard speaker and adding a very stiff spider. Essentially, that’s what an exciter is, just in a much smaller form factor. However, we must consider that attaching the exciter to the flat panel poses a risk; it can always fall off or become unglued over time, which could compromise the system's performance. Moreover, the weight of the exciter can and will introduce disturbances to the sound quality, further complicating the desired outcome.
I believe that gluing the flattened coil onto the flat panel won't add any significant weight. The weight of the coil is so minimal that it would feel as though the flat panel itself is producing the music. This approach allows for a more seamless integration, enhancing the overall sound experience without the drawbacks associated with heavier exciters. Planar speakers utilise the same idea; Magnepan, for example, employs a similar principle in their design.