[panoramer]

Hi everyone. Well like two months ago I got hocked with DML's. I can't really tell where I saw the first sample, but I ordered 10 exciters from China 40W versions of Dayton's. I couldn't order from the US because of tariffs I think I got the same ones from billionsound. Because everyone here said that EPS/XPS would be best I tried them first. When I tried some Birch Ply I threw away the plastics. They really sound unnatural and plasticy?? Wood gave me more pleasure. The best results I got from 3mm (1/8th inch). My panels are 60cmx120cm (around 2 by 4). As the last few messages suggested I've put a frame around the panel. They are hanging from the ceiling for now but a proper outer frame is in the planning. Yesterday I got some Spruce Ply as well. It's not the highest quality spruce and it's not framed from behind yet, but the first tests are amazing. Again 3mm (1/8th inch thick). Tomorrow I will also try to paint one panel with white epoxy paint. I want to copy the process of Goebels High-End speakers. They are using a wooden panel (small one like B4 paper size) and cover that one completely with fiberglass and epoxy (at last it seems like that in one of their videos and it says so in the patent documents). If it works better than plain wood I can take the panel to a UV print shop and have a photo on the white epoxy printed. Spruce panel was 125 cm x 250 cm in size (50x100 inches) and cost 21 Dollars. So worth a try I would say.   

[embty2002]

Hi everyone. Well like two months ago I got hocked with DML's. I can't really tell where I saw the first sample, but I ordered 10 exciters from China 40W versions of Dayton's. I couldn't order from the US because of tariffs I think I got the same ones from billionsound. Because everyone here said that EPS/XPS would be best I tried them first. When I tried some Birch Ply I threw away the plastics. They really sound unnatural and plasticy?? Wood gave me more pleasure. The best results I got from 3mm (1/8th inch). My panels are 60cmx120cm (around 2 by 4). As the last few messages suggested I've put a frame around the panel. They are hanging from the ceiling for now but a proper outer frame is in the planning. Yesterday I got some Spruce Ply as well. It's not the highest quality spruce and it's not framed from behind yet, but the first tests are amazing. Again 3mm (1/8th inch thick). Tomorrow I will also try to paint one panel with white epoxy paint. I want to copy the process of Goebels High-End speakers. They are using a wooden panel (small one like B4 paper size) and cover that one completely with fiberglass and epoxy (at last it seems like that in one of their videos and it says so in the patent documents). If it works better than plain wood I can take the panel to a UV print shop and have a photo on the white epoxy printed. Spruce panel was 125 cm x 250 cm in size (50x100 inches) and cost 21 Dollars. So worth a try I would say.

Hi everyone, what china exciter model, please?

[panoramer]

Hi everyone, what china exciter model, please?

I gave the specks of the DAEX32EP to an Alibaba company. They produced the same Exciter 40 W. The end cost was the same price as in the US.

Today we tried the framed Spruce Ply 5mm thick. Framed and painted. Paint didnt made a difference. Frame does add low freq. to a certain degree. Spruce ply is the best option in my opinion. If you listen to low freq. a lot you will need a subwoofer and a crossover. Spruce ply in 5mm thickness is so thin that the exciter outer shell hits the plywood and produces a rattling sound. I think this could damage the exciter with time.
Good Luck

[Kame2]

Because everyone here said that EPS/XPS would be best I tried them first. When I tried some Birch Ply I threw away the plastics. They really sound unnatural and plasticy??

You prepared your 'plastic' panels as suggested by sanding of the skin and replacing it with PVC? After this my panels didn't sound unnatural anymore.

[embty2002]

You prepared your 'plastic' panels as suggested by sanding of the skin and replacing it with PVC? After this my panels didn't sound unnatural anymore.

you mean vinyl glue?

[Kame2]

you mean vinyl glue?

Typical you use white glue. But there are pva-based craft glues that should work just as good. Mix it with the same amount of water and glue and use a foam roller to apply it to the panels. You can use a hair dryer to help drying.
There are different suggestions how many times you should treat the panel for best sound. Most treat once or twice. Someone suggested to treat the side with the exciter twice and the other side once.
After this the panel feels a bit like sand paper.

[embty2002]

Kame2 thanks
i find ESP 30kg/MC cm100X50X5 panel in my town, i'm waiting for Tectonic Elements TEAX25C10-8/SP.
what side for best SPL, considering my start panel? could I calculate with "sezione aurea 1,618" https://it.wikipedia.org/wiki/Sezione_aurea   ?
i think to build a 3 way OB speakers, with my 15" woofer A&D 1524 and tweeter monacor rbt 95, i have got an active crossover.
thanks

[Kame2]

From the NXT patent the best ratio is 1x0.88 and the second best is 1x0.73.
From my calculations the best ratio to avoid double-modes is 1x0.79 and the best ratio to get an even frequency distribution is 1x0.53.

From my experiments I can say that the ratio is not that important. What is relevant is that the smaller side limits the lowest possible frequency so it should not be to small if you want bass. The thinner the panel the smaller your panel can get without loosing bass. Considering your base panel I suggest to cut it either in three equal parts with 50x33cm or, if you want to experiment with different sizes try one 67x50 and one 50x33. But with 5mm thickness I think a big 67x50 is not needed.
With this thin panel you absolutely need a frame. If you want you can try to cut ~2 cm strips from the side of the panel and use them to build the frame. I haven't tried this myself yet, but it should be the simplest and cheapest way for the first steps with this.

edit: I just saw that you have a 5 cm panel, not 5 mm. I haven't experimented with this thick panels. Try the 67x50 variant I suggested above. And tell us how it sounds. I think 5 cm might be to thick for good quality, so if it does not sound good, try thinner panels.

[Bendingwave]

kame2quote>The thinner the panel the smaller your panel can get without loosing bass.

FINALLY!!!!! someone that gets it.


Of course there is a limit as to how thin and small a panel can get before losing all bass response.


I also agree that a 2inch panel is too thick....thinner panels bend more and thats what increases bass response.

[Bendingwave]

Here is another tip to ponder on.

Are bass and low frequency sound enhanced when using larger panels? SURE, but larger panels is not always better unless you know how to properly utilize it in ones design....Too big of a panel will make the bass sound muddy and sluggish.

In my opinion, DML/Bending wave technology is like throwing a pebble in a pond and watching the ripples flow to the edges....Bigger the pond the longer it takes for the ripples to reach the edge, the longer the bass travels the muddier/sluggish it will get if the panels are too big because it will take that much longer for the bass to travel and reach the edge before stopping.

Treble vibrations are weaker then bass vibrations so the bigger the panel/pond the weaker the treble vibrations get when it reaches the edges hence one of the main reasons for the diffused less prominent sound....the smaller the panel the more focus and pronounced the treble becomes as it has way less area to travel hence the reason why most conventional treble drivers are on the smaller side.

IMO the ideal panel size is around 24inches (2ft.) and under to maybe around 16inches give or take a few inches.


If you look at most conventional cone drivers the three biggest standard sizes is a 15inch, 18inch and 21inch. driver.

[Kame2]

In my opinion, DML/Bending wave technology is like throwing a pebble in a pond and watching the ripples flow to the edges....Bigger the pond the longer it takes for the ripples to reach the edge, the longer the bass travels the muddier/sluggish it will get if the panels are too big because it will take that much longer for the bass to travel and reach the edge before stopping.

The speed of bending waves depends on the frequency, the material and the thickness of the panel. Lower frequencies are slower. Bending waves in thinner panels are slower. You get only output from waves fitting the panel. This limits the low frequencies. In theory it should not matter if you make the panel bigger or thinner to fit lower waves.

I see this 10 kHz falloff on all my XPS 2cm panels. Seems to be material specific. The bended panel I am working on uses XPS with 5mm thickness. First tests by just holding an exciter against it suggest that they may play up to 20 kHz without falloff.

Thinking about this I come to the conclusion that it becomes problematic when the wavelength reaches the depth of the panel. So reducing the thickness of the panel increases the high frequency limit.

In summery: Make it thin!

[Bendingwave]

I think you misunderstood what I wrote as I didn't mention anything about the speed of the frequencies and or the thicknesses......What I did mention was the "SIZE" of the panel and that on a bigger/larger panel the vibrations will take longer to reach the edges then a smaller panel....For example a 12inchX12inch panel the vibrations will reach the edges before a 24inchX24inch panel as it takes longer to reach the edges of a bigger panel....The longer the vibrations have to travel without stopping on a dime means it will be muddier and or sluggish....its a fact that the ripples in a smaller pond will reach the edge of the pond before the ripples of a much larger/bigger pond which goes the same for vibrations.

I also dont buy into that theory of thinner panels equals slower bass and or that it should not matter if you make the panel bigger or thinner to fit lower waves (unless its so thin that it can bend more then a quarter of the way)...of course there are limits to how big, thick or thin a panel becomes before certain factors occur.


Thinner panels produce more output/spl then thicker panels in all frequncies but it doesnt mean its always better as too much or too little of anything is not good...it needs to be just right. 

[Kame2]

I think you misunderstood what I wrote as I didn't mention anything about the speed of the frequencies and or the thicknesses......What I did mention was the "SIZE" of the panel and that on a bigger/larger panel the vibrations will take longer to reach the edges then a smaller panel....For example a 12inchX12inch panel the vibrations will reach the edges before a 24inchX24inch panel as it takes longer to reach the edges of a bigger panel....The longer the vibrations have to travel without stopping on a dime means it will be muddier and or sluggish....its a fact that the ripples in a smaller pond will reach the edge of the pond before the ripples of a much larger/bigger pond which goes the same for vibrations.

But size and thickness (and the material, of course) depends on each other.

I also dont buy into that theory of thinner panels equals slower bass and or that it should not matter if you make the panel bigger or thinner to fit lower waves (unless its so thin that it can bend more then a quarter of the way)...

Ah, sorry my fault. As mentioned earlier I did a lot of research on this topic and therefore have lots of formulas flying through my mind. In short the basic formula for wave speed in a panel is as follows:

Code: [Select]

c = M*sqrt(2*pi*f*h)
c = speed of wave
f = frequency
h = thickness of panel
M = material constant
I will explain the physical basics in detail later when I have some time.

of course there are limits to how big, thick or thin a panel becomes before certain factors occur.


Thinner panels produce more output/spl then thicker panels in all frequncies but it doesnt mean its always better as too much or too little of anything is not good...it needs to be just right. 

Absolutely! There are limits in all direction. E.g. to thin and we loose too much damping, producing a muddy sound.

[Kame2]

You can find a basic theory of bending waves here.
There are some errors in this paper but the part regarding the bending wave speed is correct. If you combine some formulas you get the speed of bending waves as this:

Code: [Select]

c = sqrt(2 * pi * f * h * sqrt(E / 12 / (1 - u^2) / p))
c: speed of bending wave
f: frequency
h: panel thickness
E: Young's modulus (material constant)
u: poisson ratio (material constant)
p: plate density (material constant)
As you can see the speed of the bending waves depends on some constants, the frequency and the panel thickness.

You can also calculate the lowest resonating frequency of your framed panel by:

Code: [Select]

f_low = pi / 2 * h * sqrt(E / (1 - u^2) / p / 12 * (1.506^4 * (1 / x^4 + 1 / y^4) + 2 * (1 / x / y)^2 * 1.248^2))
f_low: lowest resonating frequency
x: panel width
y: panel height
To get this formular you have to dive deep into Vibration of plates.

For the highest possible frequency my educated guess is this formula:

Code: [Select]

f_high = pi / 2 / h * sqrt(E / 12 / (1 - u^2) / p)

For XPS I have found the material constants to be:

Code: [Select]

p = 40 kg / m^3
u = 0.2
E = 12000000 Pa

If you somewhere find this values for EPS or other materials we use, please tell.

[Bendingwave]

I will admit I don't understand those formulas but I do know that a DML panels size (including thickness) and density plays a big part and I know how to utilize it in my design.


I have read that article before, the funny part is that with all his technical knowledge he didn't make a DML panel to his satisfaction as this is what he states>In short, DML still has a "long way to go" to be as satisfiable as the conventional electro-magnetic loudspeaker in practice. 


After reading all that info the only conclusion he could come up with to make the DML panels sound better is using a Equalizer in which many DIY of DML have stated many times before in the past as its nothing new.




 

[Kame2]

I will admit I don't understand those formulas but I do know that a DML panels size (including thickness) and density plays a big part and I know how to utilize it in my design.

I have read that article before, the funny part is that with all his technical knowledge he didn't make a DML panel to his satisfaction as this is what he states>In short, DML still has a "long way to go" to be as satisfiable as the conventional electro-magnetic loudspeaker in practice. 

The formulas give tendencies that can help. But there is so much more you need to get a feeling for. Think of our surface preparation. Or what you said about using the frame to focus sound. This are important things that are not described by the formulas I know of.

[Bendingwave]

What are these tendencies that help? Then you go on by saying there are other IMPORTANT things not described by the formulas you know of.

Like I said before all those formulas did not help to increase the sound quality of his panels....those formulas are more of a explanation of how bending waves work on certain panel materials but it wont actually tell you how to make your panels sound better.

[Kame2]

What are these tendencies that help?

The formulas do what they do. They allow to calculate constraints. That can help to chose the right dimensions.

Like I said before all those formulas did not help to increase the sound quality of his panels....those formulas are more of a explanation of how bending waves work on certain panel materials but it wont actually tell you how to make your panels sound better.

I agree partly. You will not build the best sounding panel by just looking at formulas. You need experience for this. But you can get some experience by understanding formulas.

[Bendingwave]

One cant get experience by understanding formulas. ...What you can get is a (not always) better insight when designing your panels......This insight can also be achieved by actual hands on experience/experimentation.

Those formulas are just basic beginner understanding of bending waves on how they react on certain materials like what type of material to use , what size , what thickness , what density which is the basic questions that every one asks when getting into DML panels....other then that it has no bearing on how to increase the sound quality of ones panels, which was basically my whole point from my first response to you regarding the formulas.

[Kame2]

One cant get experience by understanding formulas. ...What you can get is a (not always) better insight when designing your panels......

Ok, we differ in what we call experience. I would totally call it a kind of experience if you understand a simplified model of the reality described by formulas. Let us agree that we disagree here and focus on the things that matter

This insight can also be achieved by actual hands on experience/experimentation.

Correct!

Those formulas are just basic beginner understanding of bending waves on how they react on certain materials like what type of material to use , what size , what thickness , what density which is the basic questions that every one asks when getting into DML panels....other then that it has no bearing on how to increase the sound quality of ones panels, which was basically my whole point from my first response to you regarding the formulas.

I think the basics are very important. And you can save some time with experimenting if you don't need to work this things out yourself.

Of course I talk to the generic you here.