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A Study of DML's as a Full Range Speaker
A Study of DML's as a Full Range Speaker
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Old 21st February 2020, 07:07 PM   #1151
Veleric is offline Veleric  United States
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Here's an interesting article I had not seen before:

Optimal design of rectangular composite flat-panel sound radiators
considering excitation location

https://ir.nctu.edu.tw/bitstream/115...9881500008.pdf

I skimmed it a few times but I'm not sure exactly what practical implications it has for us. If I'm reading it right, it seems to be implying that the optimal location of an exciter is at some particular radius from the center of the panel. Which further suggests that to find the optimum spot empirically, we don't have to test every location on the panel, we really only have to test every position along a radial line from the center.
There's still an infinite number of points to test, but it's only infinity and not infinity squared!
But I may be interpreting it all wrong.
Any other interpretations?
Eric
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Old 21st February 2020, 07:38 PM   #1152
Veleric is offline Veleric  United States
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Originally Posted by BurntCoil View Post
Great find twocents! The image I have attached from the patent is exactly what Veleric is talking about.
That patent may indeed have been where I first got the idea to try substantial damping. But this article is the one I was thinking of:

The effect of different combinations of boundary conditions on
the average radiation efficiency of rectangular plates

https://eprints.soton.ac.uk/369232/1/Eprints.pdf

I'm not sure how I found this one originally. Maybe it was from you, Burnt.

Of course, as said for the paper I just linked to in my previous post, my interpretation may be flat out wrong. But it looks to me like a pretty high level of damping should at least theoretically be favorable.

In the case of this article, they are talking about the intrinsic damping factor of the panel itself, and not local or perimeter damping.

The paper seems to be suggesting that if the correct amount of damping is built into the panel (say on the surface, or internal to the structure), the panel would provide louder, and smoother frequency response.

If true, I think one big challenge would still be to get that damping without adding too much weight to the panel.

Eric
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Old 21st February 2020, 08:05 PM   #1153
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Gosh I am going to have to read both papers again. I do remember the one you cite Eric and in particular being confused by some of the comments in the conclusion. Certainly application of damping smooths the response, and an increase in thickness increases spl’s. After that I need to sit down and work through the logic whereby in one paragraph the author claims in increase in SPL for clamped panels , which contradicts my recent experience, and then goes onto say literature exists that a freely supported panel increases efficiency as well. I might be misreading that so I will try again.

On your thoughts on integrating damping into the panels I like it. A rigid but highly attenuating foam as the meat in a 1mm ply sandwich might be an interesting direction. You can get foamed polypropylene and PET sheets as well as EPS/XPS and there are probably more types available. It maybe a nomex honeycomb with the cells filled might work as well.

One other comment from the paper that rang a bell for me was that with a highly damped panel the sound source is predominantly from the source. That for me was a bit of a warning as DMLs are supposed to be about diffused nodes of emission, or so I thought.

Hmm, reading to do

Burnt
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Old 21st February 2020, 08:37 PM   #1154
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Quote:
Originally Posted by Veleric View Post
Here's an interesting article I had not seen before:

Optimal design of rectangular composite flat-panel sound radiators
considering excitation location

https://ir.nctu.edu.tw/bitstream/115...9881500008.pdf

I skimmed it a few times but I'm not sure exactly what practical implications it has for us. If I'm reading it right, it seems to be implying that the optimal location of an exciter is at some particular radius from the center of the panel. Which further suggests that to find the optimum spot empirically, we don't have to test every location on the panel, we really only have to test every position along a radial line from the center.
There's still an infinite number of points to test, but it's only infinity and not infinity squared!
But I may be interpreting it all wrong.
Any other interpretations?
Eric
Yes I got that too Eric, start at the centre then explore the radial vectors.
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Old 21st February 2020, 08:41 PM   #1155
DMLBES is offline DMLBES
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I've been talking about dampening for ever. Even got dissed for using the word dampening to much by those that quit there dml experiments on P.E. forum. LOL

Its like no one believes me or listens until its written in an article. **** people even believe Tech Ingredients when he said no damping on panels because it reduces output. SMDH Which is the reason most of you started out with free floating panels with no damping.

Finally some of you are starting to realize the power of dampening. Any type of material with dampening properties used on the panel will effect its sound even when used as a suspension. Like I said before anything you add to the panels will effect its sound. Its not just one technique but many techniques combined that will get you better sound. Tech Ingredient claims that painting the panels have no effect on the sound which is false. Paint one panel and don't paint the other there will be a slight change in sound. If you paint the front of the panel and not the back there will be a change in sound. Paint itself can dampen the panels. Certain types of paint will dampen the panels more then others. Wood glue water mixture dampens the panels. With DML panels its all about DAMPING!!!!!! I gave yawl some hints and tips about damping you just have to go back a read my posts. lol

Of course the proof is in the pudding. Yawl need to hear my panels. I will see if I can download my panels playing on youtube with my phone but not sure the quality of the mic on the phone if it sucks then I wont do it.

Last edited by DMLBES; 21st February 2020 at 08:46 PM.
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Old 21st February 2020, 08:47 PM   #1156
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Hmmmm,

https://www.easycomposites.co.uk/#!/...bre-Panel.html
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Old 21st February 2020, 08:48 PM   #1157
BurntCoil is offline BurntCoil  United Kingdom
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A Study of DML's as a Full Range Speaker
Quote:
Originally Posted by DMLBES View Post
I've been talking about dampening for ever. Even got dissed for using the word dampening to much by those that quit there dml experiments on P.E. forum. LOL

Its like no one believes me or listens until its written in an article. **** people even believe Tech Ingredients when he said no damping on panels because it reduces output. SMDH Which is the reason most of you started out with free floating panels with no damping.

Finally some of you are starting to realize the power of dampening. Any type of material with dampening properties used on the panel will effect its sound even when used as a suspension. Like I said before anything you add to the panels will effect its sound. Its not just one technique but many techniques combined that will get you better sound. Tech Ingredient claims that painting the panels have no effect on the sound which is false. Paint one panel and don't paint the other there will be a slight change in sound. If you paint the front of the panel and not the back there will be a change in sound. Paint itself can dampen the panels. Certain types of paint will dampen the panels more then others. Wood glue water mixture dampens the panels. With DML panels its all about DAMPING!!!!!! I gave yawl some hints and tips about damping you just have to go back a read my posts. lol

Of course the proof is in the pudding. Yawl need to hear my panels. I will see if I can download my panels playing on youtube with my phone but not sure the quality of the mic on the phone if it sucks then I wont do it.
I for one would love to see and hear your work DMLBES. Looking forward to it!

Burnt

Last edited by BurntCoil; 21st February 2020 at 09:05 PM.
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Old 21st February 2020, 08:48 PM   #1158
DMLBES is offline DMLBES
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Originally Posted by BurntCoil View Post
That could work but did you see the PRICE!!!!!
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Old 21st February 2020, 09:05 PM   #1159
BurntCoil is offline BurntCoil  United Kingdom
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Unfortunately I did.
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Old 21st February 2020, 10:06 PM   #1160
Veleric is offline Veleric  United States
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Originally Posted by BurntCoil View Post
Eventually I will get around to fabricating my own version of something like that. But truth be told I'm not sure CF is the optimum skin layer. It may sound wrong but CF is actually, um, heavy, at least compared to wood. My belief is that a wood veneer skin on both sides of a very light (but hard) core could be even better than CF/foam/CF. I have come to believe that B/m^3 is critical, and on that basis, my estimates suggest wood veneer is better than CF.
Eric

Last edited by Veleric; 21st February 2020 at 10:26 PM.
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