Looking for input: Best material for mid range cone

@russ751,

You misread my post regarding aluminum drivers. It was sarcasm. I was referring to the fact that aluminum drivers are far from a new concept, yet many highly regarded manufacturers continue to use them in everything from bass woofers to tweeters.

I was making fun of some companies that use uncommom composite materials, often as a pure marketing ploy. They know the public majority has come to assume that any fiber composite material is inherently better than traditional materials, whether used for ballistic vests, car chassis’, or speakers. Consumers likes exotic materials because it leads them to believe they received a high-value product. Little do they realize that some of the best materials for speakers have existed for many decades. Some people read "hemp," "flax," "carbon fiber," "graphene," "Kevlar," and their minds instantly associate these less common materials with high performance and high cost. However, companies like YG, Revel, Spendor, Stirling Broadcast, ProAc, and others continue to prove that these materials do not necessarily perform any better as speakers than aluminum, plastic, or paper.

They don’t always understand that every composite has strengths and weaknesses and countless variations as already mentioned.

And s many of the composits do sound better than what we've had if implemented properly. 

ATC addresses off-aixs frequency response as well as dynamics with their CLD fabric cone. I was thinking about them with respect their successful low distortion, high-dynamic speakers:

"An ideal speaker system should have phase response linear with frequency, which in simple terms means that all frequencies produced by the driver reach the listener’s ear at the same time. This eliminates partial cancellation of certain frequencies due to their arrival at the listening point out of phase. Phase shift is a result of resonances in the drivers, as well as a consequence of the design of crossover network filters.

Careful driver design assures an amplitude response free from any broadband (low Q) resonance. Conventional design wisdom tells us that a stiff speaker cone is ideal for wide on-axis frequency response. However, poor off-axis frequency response and multiple resonances that color the sound make a non-flexible cone less than optimum. The conventional approach to resolving this problem is to highly damp the motion of the cone, but this dramatically reduces the efficiency of the speaker.

One of ATC’s approaches to eliminating resonant peaks in the driver is to use a heavily damped fabric cone with sufficient structural integrity to sustain high power levels. Constrained Layer Damping (CLD), an ATC innovation, uses a “sandwich” cone construction, with a damping layer molded between two lightweight fabric cones. As the cone assembly flexes, the damping material absorbs the shear energy between the two layers, offering dramatically more efficient damping than conventional methods. This design reduces harmonic distortion, minimizes resonances that affect on- and off-axis frequency response, and, since it offers less loss than standard damping techniques, dynamic headroom is improved.

The combination of mechanical damping and electrical damping from the power amplifier keeps the system tightly controlled, providing well defined bass and midrange detail."

http://www.transaudiogroup.com/wp-content/uploads/2015/06/ATC_Engineering_Goals_and_Approaches.pdf

the most transparent midrange drivers i have heard are made of aluminum.  but their properties usually need one incredible crossover to tame the break up distortion and rapidly rising response.   see the joseph audio speakers with infinite slope crossovers.