Metal-Paper-Metal laminate cones? Constrained Layer Damped Cones.
A metal-paper-metal laminate cone seems kind of obvious - structurally optimized with the stiffer material on the outer faces, should be able to damp the metal resonance, best of both worlds.
Seems practical too - not a lot of extra cost, both materials are common and easy to work, better UV and moisture resistance.
I have had the idea for a while but never seen it used in a speaker, anyone aware of any examples?
David
A metal-paper-metal laminate cone seems kind of obvious - structurally optimized with the stiffer material on the outer faces, should be able to damp the metal resonance, best of both worlds.
Seems practical too - not a lot of extra cost, both materials are common and easy to work, better UV and moisture resistance.
I have had the idea for a while but never seen it used in a speaker, anyone aware of any examples?
David
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I would think it would be too heavy. A metal-only cone is as thick as it needs to be to avoid deformation in use. Using such a lamination would mean very thin metal cones (difficult to maunfacture) with a thin paper cone (difficult to manufacture) and then trying to bond them (difficult to do). Also, making two different cones makes it much more expensive.
Some DIY dudes have laminated thin metal foils onto standard speaker cones.
If I recall correctly:
-The reasoning behind it relates to increasing the speed of the waves travelling thru the cone material (voice coil --> surround).
-There was a very enthusiastic DIY chap (Eastern European, maybe?), whose website I saw years ago. He painstakingly laminated his cones with thin alu foil, using old fashioned hide glues (basically jelly / boiled animal scraps).
His website and the fullrange forum are long gone, but this comment is encouraging.
RE: Coat paper cone with aluminium to improove sound - GM - High Efficiency Speaker Asylum
If I recall correctly:
-The reasoning behind it relates to increasing the speed of the waves travelling thru the cone material (voice coil --> surround).
-There was a very enthusiastic DIY chap (Eastern European, maybe?), whose website I saw years ago. He painstakingly laminated his cones with thin alu foil, using old fashioned hide glues (basically jelly / boiled animal scraps).
His website and the fullrange forum are long gone, but this comment is encouraging.
RE: Coat paper cone with aluminium to improove sound - GM - High Efficiency Speaker Asylum
Sandwich laminate is structurally more efficient than a solid piece, that's why it's used in aircraft, F1 cars, performance yachts and similar structures.
Thinner skins and and a low density paper core could be less heavy than a solid metal cone with the same resistance to deformation.
Thin aluminium sheet can be formed easily, for instance compression driver domes are formed with compressed air and simple dies.
I think I could even do this myself with an aluminium die.
Thin paper is hardly difficult to manufacture.
A little more complicated to have a composite cone but the cost of the cone is only a small component of the cost of a speaker, most of the cost is surely the frame, magnet and pole pieces.
Once you add the voice coil and former, surround, spider, assembly labour, leads and terminals, and so on, I expect the cone is considerably less than 10% of the total cost.
So even at twice the price it shouldn't make too much difference to the total.
Best wishes
David
I have started to laminate aluminium around my ply enclosures.
Well, started on the path to lamination.
The ply boxes are finished and I have the Al sheets.
The enclosures are rounded to reduce diffraction, so the difficulty is to bend the sheet.
This requires me to widen the bed on my hydraulic press to the size of the speakers - 1220 mm tall.
Will buy the steel fairly soon.
So a speaker project becomes a structural steel fabrication job....
Best wishes
David
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The description says only 'Al cone', but brochures are often sloppy, have you seen this personally?
Foil on both sides?
Best wishes
David
Paper can ring a lot, see the Peerless SDS 6.5" or the Scanspeak Classic (its a blend paper/kevlar) for example. When it rings, its not as nasty as a metal cone and rise in 3rd order distortion is much lower (perhaps the reason why its not that bad).
A sandwich of perforated metal and polypropylene may be a better approach, stiff but with high internal damping. Audio Technology use a similar approach in their flex units. But question is, how much would this pay off in today`s world, when graphene and carbon nanotubes stand at the corner.
A sandwich of perforated metal and polypropylene may be a better approach, stiff but with high internal damping. Audio Technology use a similar approach in their flex units. But question is, how much would this pay off in today`s world, when graphene and carbon nanotubes stand at the corner.
I think KEF did styrofoam sandwiches too, but it is specifically paper and metal I asked.
Yes, when we can make 3-d nano-trusses with carbon tubes then they really will be the ultimate material
Until then I suspect we can do better with simple laminates.
I specifically mentioned paper because it actually works remarkably well, despite the fact it seems so primitive.
So an improved paper cone at small extra cost looks pretty attractive.
I am surprised that I have never seen it, decided to ask to satisfy my curiosity.
Best wishes
David
building a cone is a handful. While the parts can be goten with some effort, you will liley go through many many cone configurations to get everything refined to point of acyually having somthing good. To start I recomend gutting any cheap cone and have a go at that first.
I have built a few cones. They were all skinned styrofoam core designs. Some skinned with foils some skinned with paper, some with glass cloth. Some were wedge shaped cores like the old KEF foam foil "cone" some were more flat shaped, some were actual cones.
My goal was a 15 inch cone with a flat FR to about 2 khz. I ended up at about 1.2 khz first break (15 db hump!). These designs were all very riggid and went of at first break sort of like a metal cone BUT were quite flat below that.
Making the cone itself is the hard part. Not that its terrably hard to do but that getting everything right is a trial and error boat load of work but endless configuration possabilites.
I have built a few cones. They were all skinned styrofoam core designs. Some skinned with foils some skinned with paper, some with glass cloth. Some were wedge shaped cores like the old KEF foam foil "cone" some were more flat shaped, some were actual cones.
My goal was a 15 inch cone with a flat FR to about 2 khz. I ended up at about 1.2 khz first break (15 db hump!). These designs were all very riggid and went of at first break sort of like a metal cone BUT were quite flat below that.
Making the cone itself is the hard part. Not that its terrably hard to do but that getting everything right is a trial and error boat load of work but endless configuration possabilites.
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I drilled a hole thru the cone to install phase plugs for somebody so have personal experience.
dave
Yes, despite FEM even the professionals seem to do a lot of 'try it and see'.
Thanks for the real world experience.
Seems like an unsuitable speaker to reduce the cone area even more.
But if the customer wanted it...
Maybe I can find a dead one and pull it apart.
If anyone has a dead NS3 please email me.
Best wishes
David
Hello Dave,
Without first checking the cone material' properties, High Youngs Modulus, High internal speed of sound, low density, high internal damping, it is all a bit of shot in the dark i.m.h.o.
And then there is the cone's shape. I suppose you are familiar with the FineCone demo's.
Apart from the fun of experimenting (yes, I like that too, it is diyaudio after all) it is very hard to make any predictions without FEM or BEM tools. .
Good luck.
Eelco
Without first checking the cone material' properties, High Youngs Modulus, High internal speed of sound, low density, high internal damping, it is all a bit of shot in the dark i.m.h.o.
And then there is the cone's shape. I suppose you are familiar with the FineCone demo's.
Apart from the fun of experimenting (yes, I like that too, it is diyaudio after all) it is very hard to make any predictions without FEM or BEM tools. .
Good luck.
Eelco
I would like to make it seamless, but thanks for the idea
The properties of aluminium are well documented.
Paper is a much more variable item, and why even professionals do a fair bit of trial and error, or so I am told.
Yes, they did stir my curiosity.
My inner would-be mathematician wants to try a paraboloid of revolution cone shape.
I asked the question mainly to learn why I couldn't find any metal-paper laminate cones, make sure it wasn't just that I had missed them.
But now I really am tempted to experiment.
I think I would need some experiments anyway, just to provide initial data for any FEM/BEM tools.
There is probably no data for losses in the laminate, that would depend critically on how the layers are bonded.
The idea would be to make the bond constrained layer damped.
Then it could be better damped, not just than metal but even than a plain paper cone.
Stiffer, less massive, better damped - that should work.
But first I have to finish the hydraulic press enhancement, I posted partly as a bit of a relaxation break before I locked in the steel order
Best wishes
David
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