Improving Polycone woofers

[Moondog55]

I have been reading Lynn Olsen again and his comments on the performance of most generic polycone woofers.

Has anyone any experience on improving the stiffness of these cones and any suggestions on relatively easy mods?/
The woofers in question are from Jaycar Australia, the 10 inch CW-2137, I have to say that I have only been playing with these naked, but when running more than a few Watts into them they do start to sound quite distorted.
I assume that what I am hearing is edge break-up.

I was thinking of adding felt pads "A La " VAFResearch and if this would aid in stiffening the edges of the cone.

Any thoughts??


I would perhaps use a different woofer if I did not already have a few of these,

[PeteMcK]

Hi Moondog, tried PVA? don't know how dammar would work on poly.
Jaycar drivers may be cheap, but with your experience & mine of them, I'm coming to the conclusion that they're not worth the bother (& I've got about a dozen hanging 'round...)

[gainphile]

Is the distortion in the lower or higher frequency spectrum?

I have a polycone Vifa P13 and was quite surprised of the distortion on the lower frequency. So perhaps it's not a brand but rather material limitation.

[villastrangiato]

This is a fascinating topic and I'm glad someone brought it up. Perhaps there are other threads concerning the "doping" of cones. I have twelve kevlar bass drivers that I've been thinking of coating to reduce the effects of out of band break up - thus allowing a higher crossover point with a more gradual slope.I've seen versions of it in different markets that were "hand coated", but there's not much info on the composition of the coating. Anyone on here have successful experience with applying epoxies or polymers to improve either rigidity, damping, or both? My thinking is a somewhat lite application that will only change mass slightly - causing a modest reduction in transient speed to go along with the lowered Fs......Any thoughts or experiences?

[Moondog55]

Yeah Peter, the problem only comes about when they are pushed to more than a few Watts.
I tried PVA on other Jaycar ploycones and it just peels off.

There is some Jaycar stuff that is really nice to listen to, but they all seem to need OB or bigger boxes than acceptable for WAF.
Hi Gainphile, I really think this is a combination HF breakup? and IM distortion as the edges of the cone start to wobble.

I got these because the 10 inch Carbon fiber woofer is SO GOOD, and on paper they model really well sealed ( for my application at least )

Maybe we should just sell this house and buy an old church, although those are getting very expensive again, they allow plenty of room for big boxes.

[planet10]

Most everything peels off polypropelene... you might try etching it with sandpaper.

dave

[Moondog55]

Thanx Dave, that was my conclusion; although I read somewhere that superglue gel works I have never tried it.
I just connected woofer to a generic 2nd order XO ( 5.8mH & 150uF ) came out of the Radio Shack sub, and far too much HF still being heard but much better
SO

It must be HF from the steep rising response common to all Jaycar poly I can hear,

Just changed cap value to 250uF, better BUT.

Maybe they will be OK with 4th LR electronic, better get the spareXO out of the cupboard and make some more cables

[PeteMcK]

re:'Any thoughts or experiences? ' - I've used dammar on some old drivers, useful for restoring colour & giving the cones some integrity, but the down side is that the stiffening of the cone gives a peak not unlike a metal cone, but lower in freq & not so high Q.

[PeteMcK]

One thing I was thinking of trying with some old drivers, just for the hell of it - fill the cone up with polystyrene foam, so they end up sort of like a round B139

[villastrangiato]

Originally Posted by PeteMcK

re:'Any thoughts or experiences? ' - I've used dammar on some old drivers, useful for restoring colour & giving the cones some integrity, but the down side is that the stiffening of the cone gives a peak not unlike a metal cone, but lower in freq & not so high Q.

Good to know. I've never tried the stuff. I've been looking at some doped copolymers - like a low viscosity epoxy with phenolic microballons added to improve flexibility and strength. Before I start "experimenting" with expensive drivers though, I'm going to consult a chemical engineer on the type and amount of catalyst - I have no idea what heating side effects can do with carbon and kevlar fibers and I certainly don't want to find out the hard way....