Yes, I already have the speakers ready, the cones are polypropylene.
I'm not satisfied with the sound of these cones, so I'm going to make another cone for them.
A powder does nothing for stability in what D A Barlow calls more stability concerning "stress and strain" in the cone.
I never understood therefore Focals polyglass cones.
Polyprop cones sound quite well already. I like them more than paper.
Just try to sandwich them with alu foil.
I did it with the thin alu foil from the goldsmith and the glue they sell for it called "Anlegemilch"
Ok. What bother you and what brand and reference are they?
Have you already dismantled one of the membrane and weighted them?
Agreed with Freedom666, powdered aluminium won't make any difference, you need to reinforce structural built ( oriented fiber seems intuitively more appropriate in that or a foil of a given material than some powder added to a mix imo).
Again i'm with Freedom about polycone. Some dislike them for reason i don't get. Preferences... Maybe it's worth a try to put alu on them. Anyway before dismantle the driver, you'll have nothing to loose as you plan to discard the poly cone eventually.
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Concerning multi way speakers. Here the crossover makes the sound.
For having a best result in a multi way you need
A well made crossover
If you want to time align them then you need digital Fir correction.
I prefer EQed fullrange drivers doped with aluminum foil.
Here you can see it with a 25cm driver fullrange, no tweeter. The cone is aluminium paper aluminium but painted black for design reasons. Measurements included.
https://www.diyaudio.com/community/threads/im-cursed.402379/post-7429777
For having a best result in a multi way you need
A well made crossover
If you want to time align them then you need digital Fir correction.
I prefer EQed fullrange drivers doped with aluminum foil.
Here you can see it with a 25cm driver fullrange, no tweeter. The cone is aluminium paper aluminium but painted black for design reasons. Measurements included.
https://www.diyaudio.com/community/threads/im-cursed.402379/post-7429777
Attachments
May i nuance your statement Freedom666? I will anyway! 
In multiway filter is (very) important but as acoustic design used. Trying to match drivers which have directivity mismatch will not sound good. Xover can help mitigate a bit the issue but this will always be a compromise.
If your acoustic design is well thought then maybe sound is on xover.
You don't need FIR to time align drivers. You need delay.
And happily it is availlable on any dsp ( FIR are not).
You can even compensate in passive for Z offset if taken care of since the filter design stage ( thanks to allpass filter cells).
In multiway filter is (very) important but as acoustic design used. Trying to match drivers which have directivity mismatch will not sound good. Xover can help mitigate a bit the issue but this will always be a compromise.
If your acoustic design is well thought then maybe sound is on xover.
You don't need FIR to time align drivers. You need delay.
And happily it is availlable on any dsp ( FIR are not).
You can even compensate in passive for Z offset if taken care of since the filter design stage ( thanks to allpass filter cells).
No matter the composition of the cone, the surface flatness (or lack thereof) is going to have serious effects on how the laminated aluminum responds. There will be more damping in a ribbed cone and more strength in a flat one. Also depends how flat the lamination job works out in either case.
I would try something like Aquaplas im favor of any other untested substance to stiffening and dampen the cone both at the same time.
Most other substances applied to the cone either dampen or stiffen the cone, so you chosing between suppressing resonances or shifting them higher up out of band.
Aside from using Aquaplas for paper cones, I like CF loaded silicone to improve dampening without adding excess weight. It also depends on where you apply the dampening compound. To remove the main surround reflection breakup on a cone driver, you need to be applying coating to the outer 1/4 of cone circumference right up to the surround roll point. Liquid latex coating works best here as well as thicker silicone rubber. This adds more mass than treating any other area of the cone, so the outcome may not be worth the reduction in sensitivity or shifting driver TSPs. This is the case with drivers which have thick rubber surrounds and metal cones. It works best on drivers with light weight cones and thin surrounds.
Sometimes the spider causes lower midrange resonances and can be dampened with a coating of thick latex on the outer diameter of the surround. Just make sure the surround can stil breath enough, otherwise you hurt VC cooling and create air flow restrictions, resulting in distortion at higher cone excursions. If the damping compound is too low in viscosity, it may run through the spider into the VC gap and render the driver useless.
Dustcaps can be the cause for breakup at higher frequencies and require a damping coating to tame sharp peaks. Only coating the DC itself is often all that is needed to avoid adding unnecessary weight to the moving assembly. The inner cone circumference right next to the DC may be part of the problem, so its better to sneak up on the desires result before going overboard with adding too much weight.
Determining which area of the cone is responsible for the breakup can be done with a piece of felt covered cardboard on a stick to hold over the cone while playing pink noise and sine waves through the driver. Another method is using blue tack compound temporarily placed on various points of the cone. Paper cones respond better to dampening than metal or plastic cones. The heavier cone material is harder to tame if it has a single sharp peak. Multiple smaller peaks make a driver sound more lively and engaging, such as on the audax PR170MO. Well engineered paper cone drivers like most Scanspeak models respond well to cone edge coating to lessen the surround reflection dip around 1k. This is their main weakness and its easy to fix.
I've never had much luck trying to stiffen a cone in hopes of better performance. It usually just ruins driver FR and sensitivity. Aquaplas is the only thing that does anything worthwhile if dealing with a paper cone. Otherwise using latex or silicone mixed with another polymer is the only thing that makes a considerable improvement IMO.
Most other substances applied to the cone either dampen or stiffen the cone, so you chosing between suppressing resonances or shifting them higher up out of band.
Aside from using Aquaplas for paper cones, I like CF loaded silicone to improve dampening without adding excess weight. It also depends on where you apply the dampening compound. To remove the main surround reflection breakup on a cone driver, you need to be applying coating to the outer 1/4 of cone circumference right up to the surround roll point. Liquid latex coating works best here as well as thicker silicone rubber. This adds more mass than treating any other area of the cone, so the outcome may not be worth the reduction in sensitivity or shifting driver TSPs. This is the case with drivers which have thick rubber surrounds and metal cones. It works best on drivers with light weight cones and thin surrounds.
Sometimes the spider causes lower midrange resonances and can be dampened with a coating of thick latex on the outer diameter of the surround. Just make sure the surround can stil breath enough, otherwise you hurt VC cooling and create air flow restrictions, resulting in distortion at higher cone excursions. If the damping compound is too low in viscosity, it may run through the spider into the VC gap and render the driver useless.
Dustcaps can be the cause for breakup at higher frequencies and require a damping coating to tame sharp peaks. Only coating the DC itself is often all that is needed to avoid adding unnecessary weight to the moving assembly. The inner cone circumference right next to the DC may be part of the problem, so its better to sneak up on the desires result before going overboard with adding too much weight.
Determining which area of the cone is responsible for the breakup can be done with a piece of felt covered cardboard on a stick to hold over the cone while playing pink noise and sine waves through the driver. Another method is using blue tack compound temporarily placed on various points of the cone. Paper cones respond better to dampening than metal or plastic cones. The heavier cone material is harder to tame if it has a single sharp peak. Multiple smaller peaks make a driver sound more lively and engaging, such as on the audax PR170MO. Well engineered paper cone drivers like most Scanspeak models respond well to cone edge coating to lessen the surround reflection dip around 1k. This is their main weakness and its easy to fix.
I've never had much luck trying to stiffen a cone in hopes of better performance. It usually just ruins driver FR and sensitivity. Aquaplas is the only thing that does anything worthwhile if dealing with a paper cone. Otherwise using latex or silicone mixed with another polymer is the only thing that makes a considerable improvement IMO.
Dust caps are responsible for lots of issues. In a non vented pole piece they create a vacuum on excursion if rigid enough and if not rigid they buckle and snap back making all kinds of noise. A very rigid dust cap and a vented pole piece are a good combo. They stabilize the cone’s resonance and depending on shape can aid in dispersion.
I ruined once some drivers with aquaplas (in German called Wasserglas) as I deluted it in water and applied too much to the cone.
Impregnating cones should be left to professionals or the producer itself who can do it adding it to the paper pulp.
One example for putting weight to some points of a paper cone worked well for the Pfleid FRS20 a loudspeaker legend from Germany in the 80ies.
I have put the small rubber weights down and later glued them back because it was only making the sound better.
Here you can see the damping of the outer edge of the cone, too.
This is a EQed fullrange driver with perfect sound. With natural time coherence.
https://www.hifi-wiki.de/index.php/Pfleid
Impregnating cones should be left to professionals or the producer itself who can do it adding it to the paper pulp.
One example for putting weight to some points of a paper cone worked well for the Pfleid FRS20 a loudspeaker legend from Germany in the 80ies.
I have put the small rubber weights down and later glued them back because it was only making the sound better.
Here you can see the damping of the outer edge of the cone, too.
This is a EQed fullrange driver with perfect sound. With natural time coherence.
https://www.hifi-wiki.de/index.php/Pfleid
@Freedom666 We used to coat eggs with Wasserglas. Interesting stuff. JBL infused it with silica and clay.
@profiguy
First I put Wasserglas directly onto the cone. Looks like stiff lacquer. Optically very nice.
Then due to vibration it springs off like broken glass and the cone looks ugly.
Later I watered the cones with deluted Wasserglas and so destroyed them.
Today to make a paper cone stiffer I only use thin layers of hair spray based on alcohol. Here it evaporates so fast it works.
But very light and thin cones you cannot treat at all because it begins to deform.
Usually the harder cone becomes unlistenable in the mids
It gets sonically right again with alu foil.
First I put Wasserglas directly onto the cone. Looks like stiff lacquer. Optically very nice.
Then due to vibration it springs off like broken glass and the cone looks ugly.
Later I watered the cones with deluted Wasserglas and so destroyed them.
Today to make a paper cone stiffer I only use thin layers of hair spray based on alcohol. Here it evaporates so fast it works.
But very light and thin cones you cannot treat at all because it begins to deform.
Usually the harder cone becomes unlistenable in the mids
It gets sonically right again with alu foil.
I'd like to suggest Nomex (Dupont) as a core material. Paper can be a good skin if BMR drivers are anything to go by.
In fact I believe it makes sense to drive any cone near its first bending node (where the mass inside and outside the VC are equal) if you have the option.
If you want to know about cone profiles you could play with FineCone, there are copies floating around the clouds.
In fact I believe it makes sense to drive any cone near its first bending node (where the mass inside and outside the VC are equal) if you have the option.
If you want to know about cone profiles you could play with FineCone, there are copies floating around the clouds.
You could 3d print them like PolyMate 3D. He designs and builds his own motors then 3D prints the baskets, cones and surrounds. You could mix in a hand made cone with Noxmex and paper or whatever you like. There is also vacuum forming for polypropylene (over a 3d printed form?). I've prototyped surrounds from cast PU resin (and a birdy told me Andrew Jones has done the same).
Just some ideas. Not nessisary going to built a successor to purifi this way.
Just some ideas. Not nessisary going to built a successor to purifi this way.