LineArray said:
An interesting approach is that of German Physiks. They use poorly damped materials (titanium or carbon fiber) and use the fact that the bending waves are most effectively radiated into the air when the wave speed in the cone is equal to the speed of sound in air.
http://www.german-physiks.com/technology/optimising-the-ddd-driver.html
Peter M.......can you explain a ''domed panel''.........this sounds interesting.
I am currently thinking along the lines of some sort of paper mache panel but haven't come to any idea that's plausible yet.
jzagaja, I'm from Polish descent, but born in Australia. You Poles crack me up!!............is that a photo of a'' monk'' playing the violin?
I am currently thinking along the lines of some sort of paper mache panel but haven't come to any idea that's plausible yet.
jzagaja, I'm from Polish descent, but born in Australia. You Poles crack me up!!............is that a photo of a'' monk'' playing the violin?
el`Ol said:
I listened to them today at the Highend in Munich and I find them superior to any conventional multi-way or fullrange system I have heard so far. Coherent, dynamic and nothing that reminds you of a metal foil.
I was astonished to hear NXT´s other baby, the Balanced Mode Radiator in Naim´s new top of the line speaker. An interesting alternative to conventional speakers, but neither the dynamics nor the neutrality of the German Physiks.
aczern said:
jzagaja said:
Thank`s!
The bending of the plate is similar to what most guitarmakers do. To tension the soundboard into a subtle dome-like shape before it is glued to the sides.
Bending the sides before glueing on the soundboard seems like a good idea, I`m gonna try it some time.
Peter
Ziggy said:Peter M.......can you explain a ''domed panel''.........this sounds interesting.
I am currently thinking along the lines of some sort of paper mache panel but haven't come to any idea that's plausible yet.
jzagaja, I'm from Polish descent, but born in Australia. You Poles crack me up!!............is that a photo of a'' monk'' playing the violin?
If you make a slightly convex(or concave) mold, you can glue a laminate into that shape. It will be much stiffer without adding weight, just because of its shape. Its the same reason for making dome tweeters domed, and not flat.
Vacuum bagging the laminate into the mold is the most easy way to do this I think.
You could get away with a thinner and lighter panel this way.
An eliptic and slightly domed panel could be fun to try, i think.
Peter
Thanks Peter, I think that this is within our reach of trying a curved panel.However, don't forget.........ALL NXT exciters have feet that are flat(designed to be mounted on a flat surface). If there is not 100% contact with the foot of the exciter, the efficiency will be compromised.
As some may already know (maybe not
), model airplane dope has a stiffening, strengthening and tightening effect on paper when dried.
I am wondering if a doped, laminate of very light weight paper (rice paper maybe?) would make a suitable panel material?
What worries me though is that it would need to be many layers thick to be rigid and would probably weigh too much in the end.
Perhaps I should look in to the real McCoy (Aramid honeycomb)and just bight the bullet ?.
As some may already know (maybe not
), model airplane dope has a stiffening, strengthening and tightening effect on paper when dried.I am wondering if a doped, laminate of very light weight paper (rice paper maybe?) would make a suitable panel material?
What worries me though is that it would need to be many layers thick to be rigid and would probably weigh too much in the end.
Perhaps I should look in to the real McCoy (Aramid honeycomb)and just bight the bullet ?.
Ziggy said:Thanks Peter, I think that this is within our reach of trying a curved panel.However, don't forget.........ALL NXT exciters have feet that are flat(designed to be mounted on a flat surface). If there is not 100% contact with the foot of the exciter, the efficiency will be compromised.
As some may already know (maybe not
I am wondering if a doped, laminate of very light weight paper (rice paper maybe?) would make a suitable panel material?
What worries me though is that it would need to be many layers thick to be rigid and would probably weigh too much in the end.
Perhaps I should look in to the real McCoy (Aramid honeycomb)and just bight the bullet ?.
I think maybe it will be flat enough for the glue to make up for the curvature of the panel. The curvature radius is going to be very large compared to the diameter of the exciter (in the same way the sea appears flat to us).
I agree, doped paper is probably going to be too heavy and not stiff enough in relation to weight.
If you want to make your own laminates:
http://www.cstsales.com/end_grain_balsa.html
http://www.cstsales.com/flexible_core.html
http://www.cstsales.com/honeycomb.html
http://www.cstsales.com/Rohacell_51_IG.html
http://www.cstsales.com/carbon_tissue.html
http://www.acp-composites.com/home.php?cat=256
http://www.acp-composites.com/home.php?cat=251
Just a thought,,,, a curved panel can possibly have a different directivity pattern compared to a flat panel, narrower on one side and wider on the other. Don`t know if this is good or bad or if it makes a difference at all.
Maybe it is good if you could have all parts of the panel at the same distance to your listening seat from the concave side?
Peter
Thanks for all the links Peter.
Phew, there's a lot to think about
Where one has to be careful is that some of these laminated concoctions may end up being heavier or even less rigid than the Gatorfoam I am currently using.
NXT themselves have admitted to using it in some of their speakers so it's pretty good to start off with I would imagine.
When I put the hard word to them, I was told(the rep. admitted) that any improvements to the Gatorfoam would be minimal compared to the cost of obtaining honeycomb materials, shipping charges, laminating them etc.
So, for the time being, a Piezo will be added to each of the panels to see if there is any extension of the highs. It may not improve anything. In fact there is a chance that sibilance may be accentuated?
Phew, there's a lot to think about
Where one has to be careful is that some of these laminated concoctions may end up being heavier or even less rigid than the Gatorfoam I am currently using.
NXT themselves have admitted to using it in some of their speakers so it's pretty good to start off with I would imagine.
When I put the hard word to them, I was told(the rep. admitted) that any improvements to the Gatorfoam would be minimal compared to the cost of obtaining honeycomb materials, shipping charges, laminating them etc.
So, for the time being, a Piezo will be added to each of the panels to see if there is any extension of the highs. It may not improve anything. In fact there is a chance that sibilance may be accentuated?
Peter M. said:
I was thinking about paper reinforced with bamboo splinters. I had already phoned someone who runs a traditional paper mill. He asked for a mail with a detailed description of what I want. This was over a week ago and I still have no response, so I guess the project is dead.
For sure there is nothing like that in Australia, but maybe in Poland or Norway?
did you see this? honeycomb here too. this looks mostly like a manger floorstander. but even pricer!
http://www.nxtsound.com/index.php?i...ws]=488&tx_ttnews[backPid]=1&cHash=807fcf67ba
http://www.nxtsound.com/index.php?i...ws]=488&tx_ttnews[backPid]=1&cHash=807fcf67ba
Ziggy said:Thanks for all the links Peter.
Phew, there's a lot to think about
Where one has to be careful is that some of these laminated concoctions may end up being heavier or even less rigid than the Gatorfoam I am currently using.
NXT themselves have admitted to using it in some of their speakers so it's pretty good to start off with I would imagine.
When I put the hard word to them, I was told(the rep. admitted) that any improvements to the Gatorfoam would be minimal compared to the cost of obtaining honeycomb materials, shipping charges, laminating them etc.
So, for the time being, a Piezo will be added to each of the panels to see if there is any extension of the highs. It may not improve anything. In fact there is a chance that sibilance may be accentuated?
You`re welcome, and thanks for letting us know about your Ziggyplanar journey.
Peter
el`Ol said:
I was thinking about paper reinforced with bamboo splinters. I had already phoned someone who runs a traditional paper mill. He asked for a mail with a detailed description of what I want. This was over a week ago and I still have no response, so I guess the project is dead.
For sure there is nothing like that in Australia, but maybe in Poland or Norway?
Here is another way to make stiff panels. Balsa and carbon fiber lattice bracing for guitars. Invented in Australia by Greg Smallman.
http://images.google.no/images?q=lattice guitar&hl=no&safe=off&um=1&ie=UTF-8&sa=N&tab=wi
Greg Smallman who pioneered this bracing style for classical gutairs selects his top wood he is looking for wood that isnt too resonant. Because it makes the sound to hard and brittle.
I once had a lattice braced guitar with apparently very stiff and resonant wood for the top, it sounded more like a banjo than a guitar
Peter
Don't know what to look for but Mr. Marek Dutkiewicz from Tonsil (bio-cellulose domes patent) would help as they do paper cones for ages however lost their place due to dispute with a prior owner (count) so telephone is dead for a while.
Prof. Farina writes he's able to measure Volterra kernels and use them to simulate sound radiation from a wooden membranes for a given mechanical properties. No matter if it's a violin or DML panel. Dr. Langhoff who was teaching at the Cremona violin maker school did build a small anechoic chamber, fitted it with a multi microphone setup, and built a special wire actuator (a steel wire pretensioned as the violin chords, and passing inside a strong magnetic field - modulating the current flowing in the wire, it was possible to apply a controlled force to the bridge of the violin, so it was possible to excite it properly in a controlled and repeatable way.
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