Looking for input: Best material for mid range cone

Polypropylene has always been a miserable material for cones. If you go back and read the reviews of speakers that employed that stuff back at it's peak, nobody had glowing things to say about it's sound. It has excellent damping, but it's got a horrible Young's modulus and mass. Somebody is making polypropylene cones doped with clay and minerals, but I can't remember who. 
Personally, I think the material is as important as implementation. Wilson is embracing paper after years of Focal W cone drivers. Magico likes their special recipe of carbon kink. B&W maintains their obsession with coursely woven plastic fibers. I think very highly of Focal's Flax Cone. Some materials just suck though, and polypropylene is definitely one of them. It is to midrange and woofer drivers what paper is to tweeters. 

@helomech,

No, like I said in another post, I didn't waste my time listening to every single $4000 speaker produced by every manufacturer on the planet. Harbeth, to the best of my understanding, basically produces highly refined BBC monitor type speakers. I'm not at all surprised Harbeth chooses to use polypropylene cones because a primary characteristic of BBC monitors is the classic British dark tone. I wasn't particularly taken with B&W because those Kevlar cones tend to be darker too. From everything I've ever read about polypropylene cones, and specifically Harbeth, I didn't bother wasting my time hunting down a pair to listen to because nothing suggested to me that they'd be to my taste. I fully realize some people would sell a testicle for a nice pair, but I'm not one of them. 

I'll put my strong support behind big planars and electrostats. More sensitive to position than an arthritic porn star though. If I had a more ideal room I may have more deeply considered a pair. My ancient AMT1's are real happy campers in my spare bedroom, much more so than my listening room, just because of the simple shape. 

That's why I like my Focal. It's very hard to end up with a lousy speaker if it's designed to exhibit good measurements all around. The buying public seems to de-emphasize measurements far more than designers and professional reviewers. I've grown to highly appreciate the measurements Stereophile does because they're very predictive of what a speaker will sound like. 

@helomech 

I've got speakers with those fancy Focal F cones. They sure as hell weren't the reason I bought them. They do what they do well. That's the bottom line. 

A lot of people put an obscene amount of emphasis on the tonal purity a driver or it's diaphragm material are capable of. To me that's a secondary consideration because I don't listen to much music where the recording engineer seemed obsessed with the tonal presentation. The space and ambience tends to be a higher priority. I bought the Focals because they're exceptional at recreating a space. Is that what flax does? Seems that way. Polyglass isn't exactly space age material though, being little more than a paper cone spritzed with micronized glass, and it does imaging better than plenty of aluminum drivers. 

Worth pointing out, Wilson is getting great results from well built paper, some say better than the Focal W cones they used in many of their products. The speed of sound through paper can approach speeds near what you see in steel if you make it right. W cones are limited in that. On the other hand, I've never heard of anyone complaining about the results Magico gets with their hyper-exotic construction and materials. 

Ultimately, I think too many people in this hobby develop strange obsessions with diaphragm materials when the world is full of exceptions to their opinions. Can a metal tweeter be smoother than a soft one? Yeah. Can paper outperform carbon fiber and Kevlar? Yeah. Can flax do better than paper? Sounds like it from where I'm sitting. Can paper humiliate everything I've ever heard? Good chance it can. I think it pays to be agnostic about such things as materials.