Looking for input: Best material for mid range cone

Stiff and light with breakup significantly out of the crossover frequency 

simple really

till you try try and build it.

look at energy storage and pistonic motion IF you are not a science denier...

I became a planar guy after I purchased the Martin-Logan Aeon 12 years ago.  Since then, I have owned Magnepan 1.7 and Quad ESLs (I think the model was 2805) .  I still have the Maggies, but I am not using them.  A few months back I purchased a pair of Kipod 2 speakers used at a very nice price.  The Kipod speakers use aluminum speakers machined from blllets of solid aluminum for the midrange and woofer.  While they are very expensive if purchased new, you can expect to pay 25% of the  new cost for a good used pair.  These speakers are incredible in the midrange and the soundstage, tone, etc. are spectacular.  I prefer the sound of the Kipods over any speaker I have ever heard.  Save your pennies and look for a good pair of used Kipods or other YG speakers with aluminum drivers. 

@russ751,

How can the Kipods be any good when made of such an antiquated material? Don't you know that good speaker drivers require super exotic composite materials, the more exotic the better......😂

Actually that's not at all what it being said. What's being said is that many companies are using better quality materials and implementing them properly.  To take a good thread and make a post that sarcastically puts down good companies is silly isn't it?  

Just look at the measurements of these drivers that utilize new materials and driver concepts.  Hard to argue with great measurement AND great sound.  Have you heard the Vandersteen 7 mk2's set up properly?  What about the other speakers that are using up to date technology?  Maybe you have, but to make a blanket statement like that says otherwise.  

Not one person has said anything negative about the other posters love of his speakers, so not sure why you would have a sarcastic comeback.  Interesting...

I am repeating a bit. The textbook ideal material avoids resonance leading to phase distortion.  Another issue is avoiding frequency dependent vibration transmission radially through the cone, a property of solid materials but not air. (ESL is a clever answer as they do not require rigidity to avoid phase/distortion issues). Then the quality of material can depend on the manner in which it fails to handle those objectives, e.g. damping. These failings lead to a multitude of designs to approximate the ideal. A tip-off to complexity is the plethora of blended materials in cones. A lot of other factors come in to play that have been mentioned, and another is cost. I think it is hard to say what is best without more qualification. 

I have a pair of old, $2K speakers with Vifa PP midrange drivers. The midrange is certainly not THE best, but it is great compared to competition at that price including Paradigm.