Question about a Kevlar cone

[SQdude]

A certain manufacture is famous for using yellow Kevlar cones with a totally flat surround housed in a sphere. I'm curious is the general break-up characteristic of Kevlar (what freq does this material fall apart at)? Also, with a flat surround, how much xmax do you really think they are getting out of this driver? Just curious because few off the self manufacturer's top products utilize Kevlar and such a surround. What "sound" does Kevlar have (tonally is it dark, bright, detailed, etc)? I'm also intruded by the sphere they use, which is tapered internally, science or voodoo?

Thanks

[joecarrow]

You aren't talking about B&W, are you? If so, I think the kevlar speaker you're taking about is really more of a midrange than a woofer.

Breakup frequency is dependent on cone geometry, but kevlar is fairly stiff and light, allowing this frequency to potentially be high. I don't know what B&W does for crossovers, but as far as I can tell they seem to run their woofers to higher frequencies than what I would call conventional. Overall, though, I would say that their approach to design is based on sound engineering more than gimmicks or snake oil. The sphere is one of the best external shapes for a speaker for diffraction purposes, and a tapered tube is one of the better internal shapes for a speaker for controlling and preventing unwanted internal resonance. The sphere is a horrible internal shape, though, so you don't see a lot of manufacturers use it.

Another example of a company using kevlar is Scan Speak. Linkwitz used their kevlar woofers in a really old project on his website- http://linkwitzlab.com/m_panel.htm

They're not available anymore as far as I know.

Regarding the "sound" of kevlar- I think that overall speaker and crossover design has a far larger effect on the sound than the woofer material. If I had to guess at a material based impact, though, I'd say it's probably somewhere between paper and metal. I believe that driver design has advanced beyond most of B&W's drivers, but they've kind of built up a signature look around the yellow cone.