Looking for input: Best material for mid range cone

mmeysarosh51 posts07-04-2017 10:24pmAny material used in diaphragm will have properties that require attention to gain optimal operation. Beryllium as an example has very high self damping (stiffness of cone) but doesn’t exhibit much internal damping (ability to dissipate excess energy within the material). While the operating range of one will be greater, care to ensure you stay within its operating range for its given size and construction.

I would like to address carbon fiber, since its brought a number of times but aspects of it should be known. There are so many grades of carbon fiber and the epoxies used, construction method employed, and design parameters in that you can come to some very wildly different results with the very same material. You could spend an considerable amount of time in FEA design between differing grades, weaves, shapes, etc. The modulus alone could vary by a factor of five just by simply changing from a low modulus to high modulus fiber. The expense of high modulus fiber is notably more and typically forgoes some tensile strength when modulus increases. But in this application, tensile strength matters little with it being well beyond what is required in nearly all grades. The latest development in this area has been the infusion of graphene in the epoxy, which aids in producing a more uniform carbon fiber sheet. This will further extend how light a driver cone could be made without any loss of stiffness. This still doesn’t account for the mass of the voice coil, former, surround, etc.



I agree that you must take into account a complete design as I've stated before. When your looking for the best material, it must include a completed design. Only with this, combined with the desired operating range and crossover implementation could one select the best material within a given cost. I do mention cost since its very easy to gain a marginal improvement for an extreme cost, one which is better spent in other areas of the system.
Yes any driver needs to be a total design involving all of its components. You are correct in saying all materials have a distinct sound that is why the Vandersteen Model Seven drivers (tweeter, mid, mid-bass) use extreme modulus uni pre-preg with high modulus graphene loaded matrix 29% front and back with balsa as a truss form and damper between them. Balsa has 8 times the compressive strength of rohacell yet is a very effective noise damper (note used in Corvette floorboards to damp road noise). All this used in all drivers involved 100Hz and above offers less color or sonic characteristics then ever achieved.

@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.