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Metal-Paper-Metal laminate cones?
Metal-Paper-Metal laminate cones?
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Old 7th February 2018, 01:33 AM   #1
Dave Zan is offline Dave Zan  Australia
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Default 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

Last edited by Dave Zan; 9th February 2018 at 11:01 PM. Reason: Added 'Constrained Layer Damped' to title, in an effort to attract attention of more experts.
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Old 7th February 2018, 02:11 AM   #2
Tromperie is offline Tromperie  Australia
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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.
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Old 7th February 2018, 03:44 AM   #3
hollowboy is offline hollowboy  Australia
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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
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Old 7th February 2018, 03:54 AM   #4
hollowboy is offline hollowboy  Australia
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Sort of on-topic:

I've considered building enclosures this way, as a aluminium-foam-aluminium sandwich.

They'd be good for shed / workshop / outdoor use, where the extra wall bulk wouldn't be a problem, but being lightweight + weatherproof would be a bonus.
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Old 7th February 2018, 04:20 AM   #5
Dave Zan is offline Dave Zan  Australia
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Quote:
Originally Posted by Tromperie View Post
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...
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.

Quote:
such a lamination would mean very thin metal cones (difficult to maunfacture) with a thin paper cone (difficult to manufacture)...two different cones makes it much more expensive.
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
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Old 7th February 2018, 04:57 AM   #6
planet10 is offline planet10  Canada
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Metal-Paper-Metal laminate cones?
The Aura NS3 is a metal-paper laminate.

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Old 7th February 2018, 06:56 AM   #7
Dave Zan is offline Dave Zan  Australia
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Quote:
Originally Posted by hollowboy View Post
...enclosures this way, as a aluminium-foam-aluminium sandwich...
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

Last edited by Dave Zan; 7th February 2018 at 07:06 AM.
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Old 7th February 2018, 07:03 AM   #8
Dave Zan is offline Dave Zan  Australia
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Quote:
Originally Posted by planet10 View Post
The Aura NS3 is a metal-paper laminate.
The description says only 'Al cone', but brochures are often sloppy, have you seen this personally?
Foil on both sides?

Best wishes
David
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Old 7th February 2018, 07:18 AM   #9
capslock is offline capslock  Europe
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There were also the Görlitz cones, styrofoam with aluminum foil on both sides.
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Old 7th February 2018, 07:47 AM   #10
Mario Pankov is offline Mario Pankov  Europe
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Metal-Paper-Metal laminate cones?
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.
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