Jaxboy.
Thanks, that is nice of you to say.
There are so many ways to use the DML technology, it is just a question of which suites you and fits in with your lifestyle.
We all seem to have our own ideas which is the perfect one for ourselves.
But that is what it is all about.
Were you able to try my coffee whizzer idea, I thought it could be of some use to you ?
The benefits went down to about 2k ,well within your hearing range.
Steve.
Thanks, that is nice of you to say.
There are so many ways to use the DML technology, it is just a question of which suites you and fits in with your lifestyle.
We all seem to have our own ideas which is the perfect one for ourselves.
But that is what it is all about.
Were you able to try my coffee whizzer idea, I thought it could be of some use to you ?
The benefits went down to about 2k ,well within your hearing range.
Steve.
Hello Spassgeneral,
There are few realizations (or communication?) about the canvas panel and in my knowledge no scientific approach... so on my side, I tried to copy the already existing panel. Where mine are different (by accident) is the pad (central wood piece) is made of real balsa where most of the other are from real light plywood. In a first intention, I would encourage to copy to have a starting point... and not be disappointed. It is up to you to follow the standard path or the pioneer one.
My panel are made with a 33x41cm canvas and go down 40Hz.
Compare to a standard DML, there is a kind of boost of the first mode (first resonance). The only reason I see to go to a larger canvas is to change the mode separation to get a smoother response but then what is the best ratio (see Veleric work on plywood?).
One drawback might be to have to low resonances which might be to long to stop.
No other way than somebody makes the test...
Christian
PS : below the panels I know (see the historic file with link with my signature on the left of the post frame)
PS2 : my canvas have now a spine (needed at least to avoid any effect of the exciter mass)
The petal/leave is free standing, only fixed at the top, but vibrates with the voice coil on the bottom.
Everything that pulsates doesn't give out sound. If all the flags at a soccer match would give out sound...
Well, its all about electricity. Whatever we "hear" is actually turned into electrical signals by the inner ear, which the brain translates as sound. A microphone turns the "sound" into electrical activity, a voice coil turns the electrical activity to sound. Some things connected to the voice coil amplify the "sound".
Well, if you can find a tall tin can, simply slit it into those petals, push it little bit down, you can have that "woofer." The black tea from China was sold in such cans, once. There are some tall beer cans too, I believe.
And, it is all about distributed mode through the petals.
It doesn't have to look like a split rugger ball, the top can be open and stiff. The petals don't really have to visibly vibrate, for the sound to amplify. I used a spiky glass candle holder for experimenting once.
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chdsl,
The pedals are fixed both at the top and bottom and the pedals are 0.5mm thick The sphere is 76mm diameter. I have not put any acoustic damping material on the inside yet. The sound does appear to be coming from all surfaces, it appears to be an acoustic point source.
I am going be setting up my laser velocity (microscope) that measures vertical displacement. It has a 100 micron spot size (sample area)and can measure displacements down to ~500 nanometers at frequencies up 100KHz. My plan is to mount the sphere in the center of a goniometer three axis stage to measure along a tangent line to see the vibrational response of the petal. A quite dirty test of measuring at the equator I was seeing about 10 micron displacement at 10KHz.
The pedals are fixed both at the top and bottom and the pedals are 0.5mm thick The sphere is 76mm diameter. I have not put any acoustic damping material on the inside yet. The sound does appear to be coming from all surfaces, it appears to be an acoustic point source.
I am going be setting up my laser velocity (microscope) that measures vertical displacement. It has a 100 micron spot size (sample area)and can measure displacements down to ~500 nanometers at frequencies up 100KHz. My plan is to mount the sphere in the center of a goniometer three axis stage to measure along a tangent line to see the vibrational response of the petal. A quite dirty test of measuring at the equator I was seeing about 10 micron displacement at 10KHz.
Steve,
I have had 8 operations on my eyes over the years, resulting in myriad floaters and nothing being in sharp focus. As a result, I'm not so sure that my solder connections to my amps have been all that good. Add to that getting 3 bad-from-supply amps from China in a row, and not willing to risk the one amp that does work by running it at 2 ohms, I just gave up on being able to use my DMLs. (My exciters are 4 ohm, as are the other speaker set I was to use in the rear.) I have a college degree in electronics, plus 20 years repairing electronics in the military, but a lot of good that does me when I can't see what I'm doing! Too bad, because the DMLs sounded so good! I just have to experience DMLs vicariously by reading what you and the other contributors are doing.
I have had 8 operations on my eyes over the years, resulting in myriad floaters and nothing being in sharp focus. As a result, I'm not so sure that my solder connections to my amps have been all that good. Add to that getting 3 bad-from-supply amps from China in a row, and not willing to risk the one amp that does work by running it at 2 ohms, I just gave up on being able to use my DMLs. (My exciters are 4 ohm, as are the other speaker set I was to use in the rear.) I have a college degree in electronics, plus 20 years repairing electronics in the military, but a lot of good that does me when I can't see what I'm doing! Too bad, because the DMLs sounded so good! I just have to experience DMLs vicariously by reading what you and the other contributors are doing.
The bottom is of the petals are fixed to voice coil, I believe. If you are about a meter or two from the woofer, do you feel that the sound comes from there, or just from anywhere? Do you feel the sound is coming from below the equator, or above it? I like your design. If you keep the gaps open after placing the acoustic damping material, those gaps may work like many bass-reflex outlets. Awaiting your progress.
Too bad (sorry if my English is not accurate enough to translate my feeling). No options of "young" eyes around you under your instructions to lead the operations?
Christian
homeswinghome,
I am adrift in a sea of estrogen with my daughter, granddaughter, and 2 female dogs. Both humans barely tolerate my musical taste, and I am called upon to do every task involving tools or anything that could remotely be construed as having to do with engineering. Thus, asking one of them to check my solder joints would be akin to asking me to apply their makeup for them.
I am adrift in a sea of estrogen with my daughter, granddaughter, and 2 female dogs. Both humans barely tolerate my musical taste, and I am called upon to do every task involving tools or anything that could remotely be construed as having to do with engineering. Thus, asking one of them to check my solder joints would be akin to asking me to apply their makeup for them.
chdsl,
Wait, what?
True, everything that pulsates doesn't give out sound. Some things pulsate too slowly, or too fast, or with insufficient speed or magnitude to give out sound... But...only things that pulsate give out sound. Things connected to a voice coil amplify sound if and only if those things vibrate/pulsate.
Mechanical vibrations of physical objects (diaphragms, plates, cones ribbons, whatever) create pressure waves in the air, which drive our eardrums.....and eventually the brain translates as sound. But if there's no vibrating physical object to create pressure waves, there is no sound.
Do you agree about that?
Yes, I'm sure there are some obscure ways to trick the brain into thinking that the eardrum is moving, and making the brain "sense" sound, but that would be neuroscience, not loudspeakers.
Eric
Smokin' Chladni Plate!
Ever since I started playing with DML's, I've been trying to perform a decent Chladni plate demonstration. My previous attempts were disappointing. But after playing around with a glass plate I started to wonder if a glass plate wouldn't be ideal, considering that it is low damping (and hence had very strong resonances), combined with its exceptional flatness. And today: success! Well kind of....
My FEM predicted this mode shape at about 554 Hz, which I thought was pretty cool:
And at virtually the exact frequency my plate did this!
Sadly, at virtually the same moment, I began to see (and smell) the smoke from my overheating exciter! oops...I think the exciter, which was taped to the plate on the lower left, just outside the image, is fried! I never even felt one get warm before, but I was a little afraid to even touch this one!
Eric
Ever since I started playing with DML's, I've been trying to perform a decent Chladni plate demonstration. My previous attempts were disappointing. But after playing around with a glass plate I started to wonder if a glass plate wouldn't be ideal, considering that it is low damping (and hence had very strong resonances), combined with its exceptional flatness. And today: success! Well kind of....
My FEM predicted this mode shape at about 554 Hz, which I thought was pretty cool:
And at virtually the exact frequency my plate did this!
Sadly, at virtually the same moment, I began to see (and smell) the smoke from my overheating exciter! oops...I think the exciter, which was taped to the plate on the lower left, just outside the image, is fried! I never even felt one get warm before, but I was a little afraid to even touch this one!
Eric
High WAF is certainly critical. But the idea (of this thread, anyway) isn't really just to have a "flat panel" give out the music. Rather, the idea is to use a panel that is large enough (relative to its stiffness) to give out music primarily by bending (i.e flexural) waves instead of rigid pistonic motion. It can indeed be argued that at the lowest frequencies, a typical dml will behave in a "quasi-pistonic" way, but that is not the way a true dml (i.e bending wave/flat panel speaker) performs over the vast majority of its frequency range.
I do think that the APM and similar speaker videos you posted are really cool and appreciate that you shared them. But the more I understand them, the more I think they are not really "flat panel speakers".
Eric
I tend to agree. Interesting although the MBL approach is this thread will lose value if it becomes a generalised ideas thread. There have been threads on the pulsating sphere approach in the forum in the past and I am sure new posts to these, or starting a new one on the topic, would be welcomed by those interested in the technique. I am considering a new thread on DIY exciter design which, although directly related to DML’s , will likely involve topics that are more related to general transducer design than DML’s, so a new thread keeping this one pure DML seems like the thing to do to me.
Burnt
Burnt
When you hit a rail (in a railway) few kms away, do you see it vibrating? But if you put an ear to it, you'd hear that knock. When a little child jumps up and down a floor above, or few rooms away, you hear the sound, which sometimes annoys old people, but you don't find the building vibrating, do you? Standing on an empty road, you feel, or your legs feel that a vehicle is approaching, even when you can't see it for quite a while. The road doesn't vibrate.
Mechanical vibrations of physical objects (diaphragms, plates, cones ribbons, whatever) doesn't create pressure waves in the air, the sound simply travels through air, which is a very low density medium. The speed of sound is very high in steel, aluminum, glass, timber etc, many times more than in air.
Brain is not tricked. The inner ear, which translates the sound the ear 'hears' into electrical signals to brain, which interprets those signals as it had been taught/trained. Anyway, I posted a link how the ear hears a few posts earlier.
Do you think the 'exciter' you have doesn't have the 'pistonic' motion?
What do you understand by "bending" the waves?
@chdsl
You may find the following useful
https://ccrma.stanford.edu/~jay/subpages/Lectures/Lecture1-Acoustics.pdf
Burnt
You may find the following useful
https://ccrma.stanford.edu/~jay/subpages/Lectures/Lecture1-Acoustics.pdf
Burnt
The second sentence says he is wrong. I don't find any wind in the room, not even near the speakers. I just heard a car being parked. I can't see it, but I can say exactly where it was parked. The car park is behind me two walls away. The walls didn't 'hear' it, but the speed of sound increased many times in the walls, but also lost its intensity travelling through heavy mass.
Here's a guy using 3 speakers on a triangular glass panel. The voice coils don't touch the glass panel, neither the cones. 4 years ago.