With "Wasserglas" (german) in english sodium silicate
https://en.m.wikipedia.org/wiki/Sodium_silicate
I ruined expensive paper cone drivers.
Hair liquid has more alcohol drying faster away.
https://en.m.wikipedia.org/wiki/Sodium_silicate
I ruined expensive paper cone drivers.
Hair liquid has more alcohol drying faster away.
One can achieve similar result with Damar varnish, or any other varnish diluted 50/50.
But, but, there's a risk that varnish can add to cone mass.
My best results have been with wood dye, spirit based. Easily verified with an impedance sweep with LIMP.
But, but, there's a risk that varnish can add to cone mass.
My best results have been with wood dye, spirit based. Easily verified with an impedance sweep with LIMP.
After I applied wax to some really thin (3.4mm) speaker cabinets, they seemed to have a higher frequency from the "knock" test, presumably from hardening the wood; could this work with paper cones?
If there was a good way to stiffen paper cones, wouldn't speaker manufacturers do it?
If there was a good way to stiffen paper cones, wouldn't speaker manufacturers do it?
Be careful making it too stiff… you will introduce HF bringing.
I have used many things, lacquer like Damar you have tobe very careful.
I mostly use Puzzlwkoat/ModPodge, been doing paper cone drivers since the late 70s. For a woofer maybe a number of coats each side. On FRs a little as possible.
Never met a driver that wasn’t better after (a long as not overdone)
dave
I have used many things, lacquer like Damar you have tobe very careful.
I mostly use Puzzlwkoat/ModPodge, been doing paper cone drivers since the late 70s. For a woofer maybe a number of coats each side. On FRs a little as possible.
Never met a driver that wasn’t better after (a long as not overdone)
dave
Preparing a 30cm driver for subwoofer use.
Stiffening technique with polystyrol (here dishes for eating).
Forming a "bridge" for the center.
And using silicone seal.
Put a weight on and let drying one day.
Putting a weight on the polystyrol cone.
Its only functional it does not need to be "nice" as the subwoofer driver will not be visible.
Stiffening technique with polystyrol (here dishes for eating).
Forming a "bridge" for the center.
And using silicone seal.
Put a weight on and let drying one day.
Putting a weight on the polystyrol cone.
Its only functional it does not need to be "nice" as the subwoofer driver will not be visible.
Who does not like the look could add aluminium foil to the polystyrol adding some more stiffness.
However in this example the stiffness is a result of the depth of the construction.
Aluminium foil can be used for making a sandwich cone.
However in this example the stiffness is a result of the depth of the construction.
Aluminium foil can be used for making a sandwich cone.
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Be very careful with varnish. Too much causes HF breakup modes which can be very problematic. Many 40-1197 were killed by too much damar. The stuff has a very nice smell. Probably not good for you.
dave
Edit: seems i am repeating myself.
more orthodox diy cone stiffening using
a big dustcap
on a 15cm driver
the subwoofer inside the box is with 1cm concrete and only 3mm wood panels just offering the form for it
a big dustcap
on a 15cm driver
the subwoofer inside the box is with 1cm concrete and only 3mm wood panels just offering the form for it
If only beryllium was safer to use, the ultimate stiffening material? Stiffer than steel, almost as light as magnesium, and isotropic (and highly toxic to work with!)
So all the big companies and their research labs haven't figured this out or rejected the improvements due to cost or production challenges?
//
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@Mark Tillotson
beryllium is very expensive and difficult to process.
I have very good experience with simple aluminium foil already giving the tensile strength to make paper cones much stiffer is used one or both sided.
It also protects paper cones from humidity.
With silicone sealant you get a constraint layer damping.
The dustcap stiffening trick works good due to giving stability through the big space between cone and dustcap added.
Here on the theory of it
Here about the theory:
D.A. Barlow: The Development of a Sandwich-Construction Loudspeaker System. Page 159-171. From the AES anthology of articles on loudspeakers, article written 1970.
Citation begin (page 160):
"As paper cones are thin, these resonances are bending modes. The stiffness of a material in bending, for any given geometry and edge condition, is proportional to Young`s modulus and the cube of the thickness, ignoring variations in Poisson`s ratio. ... On this basis, paper is much stiffer than metals (except beryllium) in spite of its much lower modulus, and lower density materials such as expanded plastics are even stiffer, as may be seen in Table. A method of obtaining still greater stiffness is sandwich construction. ... In bending, the maximum stress and strain occur at the outer fibers, the material at the neutral axis being unstressed. Better use of material can thus be made by concentrating it at the outer fibers. A familiar example is the tube. In the case of large areas, the same effect is obtained by using a thin high-modulus material for the outer surfaces, and a light-weight material or form of construction for the core. ... This sandwich will of course be much stiffer than the same total weight of either material used separately. The skin material should have the maximum ratio of modulus/density. Beryllium, the best material, is impractical due to difficulty of rolling and possible toxicity, so aluminium is the obvious choice. The core should be as stiff as possible in the thickness direction and have minimum density. Honeycomb aluminium or impregnated paper are frequently used in aircraft construction and could be used for flat diaphragms."
Citation end.
beryllium is very expensive and difficult to process.
I have very good experience with simple aluminium foil already giving the tensile strength to make paper cones much stiffer is used one or both sided.
It also protects paper cones from humidity.
With silicone sealant you get a constraint layer damping.
The dustcap stiffening trick works good due to giving stability through the big space between cone and dustcap added.
Here on the theory of it
Here about the theory:
D.A. Barlow: The Development of a Sandwich-Construction Loudspeaker System. Page 159-171. From the AES anthology of articles on loudspeakers, article written 1970.
Citation begin (page 160):
"As paper cones are thin, these resonances are bending modes. The stiffness of a material in bending, for any given geometry and edge condition, is proportional to Young`s modulus and the cube of the thickness, ignoring variations in Poisson`s ratio. ... On this basis, paper is much stiffer than metals (except beryllium) in spite of its much lower modulus, and lower density materials such as expanded plastics are even stiffer, as may be seen in Table. A method of obtaining still greater stiffness is sandwich construction. ... In bending, the maximum stress and strain occur at the outer fibers, the material at the neutral axis being unstressed. Better use of material can thus be made by concentrating it at the outer fibers. A familiar example is the tube. In the case of large areas, the same effect is obtained by using a thin high-modulus material for the outer surfaces, and a light-weight material or form of construction for the core. ... This sandwich will of course be much stiffer than the same total weight of either material used separately. The skin material should have the maximum ratio of modulus/density. Beryllium, the best material, is impractical due to difficulty of rolling and possible toxicity, so aluminium is the obvious choice. The core should be as stiff as possible in the thickness direction and have minimum density. Honeycomb aluminium or impregnated paper are frequently used in aircraft construction and could be used for flat diaphragms."
Citation end.
Not sure the varnish does anything at all if it doesn't add to cone mass.
What do you see 'before & after' on the impedance sweep? A sketch will do if you don't have any saved LIMP sweeps.
Varnish is the secret souce in the acoustics of violins for instance - though I believe its quartz-dust filled varnish in that case.
@kgrlee
the variations of hard cones I know of are:
Rohacell as a core (better damping than polystyrol)
and carbon fiber for covering it
Morel did a driver (expensive one) which looks pretty good as a fullrange with these materials
Eton
using Kevlar honeycomb core and kevlar coverings
which got over the years better damping maybe due to dampening glue
DA Barlow is explaining the theory in a compact way.
the variations of hard cones I know of are:
Rohacell as a core (better damping than polystyrol)
and carbon fiber for covering it
Morel did a driver (expensive one) which looks pretty good as a fullrange with these materials
Eton
using Kevlar honeycomb core and kevlar coverings
which got over the years better damping maybe due to dampening glue
DA Barlow is explaining the theory in a compact way.
@Mark Tillotson
I never tried varnish but hair spray liquid.
Its good for bass but for fullranges these get after treatment aggressive in the mids.
I used hair spray liquid and later (after drying) added aluminium foil -what worked well due to the dominating influence of the metal foil.
I never tried varnish but hair spray liquid.
Its good for bass but for fullranges these get after treatment aggressive in the mids.
I used hair spray liquid and later (after drying) added aluminium foil -what worked well due to the dominating influence of the metal foil.
Morel SCM634 it was tested in german diy magazines
https://www.morelhifi.com/en/products/raw-drivers/supreme-45/scm-634-442
the waterfall looks pretty good, too. As I remember.
https://www.morelhifi.com/en/products/raw-drivers/supreme-45/scm-634-442
the waterfall looks pretty good, too. As I remember.
