From a SQ standpoint, what are the best materials for Subwoofers, Midranges and Tweeters to be made of (in terms of the cone/dome material) and what characteristics of the materials make them so good?

I know that many home audio setups (built for sound quality anyway) use treated silk for the tweeter dome because it gives a very transparent sound. Does this necessarily translate into the world of car audio? What about metal domes (the splits I use are made of a metal called Kaladex for the tweeters, is this any good) and metal cones such as in Eclipse's range of mids and subs?

I ask mainly because I spotted an article on Focal's new Berillium 3-way splits wich touted the material (Berillium) used in the construction of the tweeters as the best material available for the application.

Any thoughts?

best = subjectivity.

it all depends on how u percieve "good" sq.

i might think metal dome tweeters sound great, whereas u might think soft domes sound better...

as for the focal BE's...who cares, no one here can afford them anyway!!!

i prefer silk for tweeters but i also use home audio tweet's in my car.

midbass i like paper, nothing seems to sound as good as it

subs anything stiff..

Tweeters... I prefer silk too...
Mine are currently titanium domes, and they can sound a bit harsh (although i believe I have almost fixed it, either that or i'm getting used to the sound.)
The silk tweeters i've heard just sound so much more... soft? I guess transparent is the word for them.

For subs and woofers, i'm impartial... My woofers are pressed fibreglass, but i've heard some treated paper ones that are very nice.
Subs the same, although i'd say something tougher then basic paper probably, so it can cop a bit of abuse.

"Magnesium, due to its lightness, slow sound transportation, and natural dampening from low hardness, would seem the best metal for cones with modest physical stress. i.e. tweeters, midranges and low Xmax high efficiency woofers. A Mg bell would not ring very well.

Titanium is significantly heavier, denser, and stronger, than magnesium. This would make Titanium well suited to subwoofers.

Aluminum's physical properties are close to magnesium. Al is 1.6x heavier, but has lower tensile strength unless alloyed, and absorbs less vibrational energy. Aluminum is much cheaper than magnesium. Most Al alloys, like 6000 series, have higher tensile strength than Mg. Al cone break-up modes are slightly worst than MG due mainly to the higher mass/strength ratio.

Carbon fiber appears to be the best long term cone material for midrange and high efficiency woofers. The ideal carbon fiber cone would likely be a curve-linear profile woven from continuous fiber before thermoset in resin. When a Tiawan company invests in this technology, we could see a new plateau in cone technology. Today, most carbon fiber cones use coarse random fibers in resin, or a cut sheet glued into a linear profile.

Today, low cost Kevlar fibers are smoother and easier to weave than carbon fiber, and hence top labs like B&W have been able to bring up manufacturing lines for woven midrange cones. The weaving technology, cone profile, and resin strongly determine the break-up modes.

element ....Density.....Velocity...Young.. Rigity..Bulkmod..mineral... Brinell..Tensile Strength
Titanium ......4057...... 4140...... 116...... 44...... 110...... 6...... 716...... 345
Aluminum ......2700...... 5100...... 70....... 26....... 76.... 2.75..... 245...... 179
Magnesium .....1738 ......4602 ......45 .......17 .......45 .....2.5 .....260 ......275
Beryllium .....1848 .....13000 .....287 ......132 ......130 .....5.5 .....600 ......300

Carbon Fiber ..1780 .....3200 ......250 .......38 .......80..... 2.6 .....235 ......276



DensityKg m-3
Velocity sound m/s
Young’s modulus /GPa
Rigity modulus /GPa
Bulk modulus /GPa
Mineral hardness
Brinell hardness /MNm-2
Tensile Strength MPa"

This is quoted text i got from another forum and i cannot confirm it's validity. Softer cones (paper, poly, etc) would fare much worse in all those things, they damp out breakup nodes but have higher levels of distortion in the passband (in general). Personally i would take a well-designed rigid cone driver over a well-designed soft cone any day of the week, but this is a subjective issue and supporters of both sides make good points about their pros and cons. Dan wiggins from adire audio, for example, is a big fan of soft cones. Other gurus like Siegfried Linkwitz use magnesium cone SEAS Excel drivers for his top of the line Orion loudspeaker, and his website justifies their use with measurements very persuasively.

Here is another writeup i came across some time back which provides (IMO) another, very balanced viewpoint:

"There are often discussions about what kind of cone material sounds the best. There is no single answer for this and everyone has an opinion. One thing for sure however is that a type of cone can be classified by it's stiffness and internal damping. When sorted by these attributes, there is a wide variety of cone materials with polypropylene on the soft end and magnesium or aluminum on the hard end.

Top end frequency response of soft cones roll off smoothly and hard cones have breakup nodes. No debate about that. Poly cones actually do have breakup nodes but they are damped into non-existance. Many manufacturers use composite cones to reach a specific combination of stiffness and internal damping. Focal W-cones, Peerless sandwich cones, Vifa wood pulp, and even poly coated paper fall into the composite category. These manufacturers are trying to reach a happy medium.

Time for the truth telling. Any kind of internal damping robs detail from the original sound. If you were to compare a high resolution waveform reproduced through a soft poly cone with the original waveform, you'll see that the waveform has been smoothed out slightly. Peaks are rounded off and information is lost or distorted as energy is stored and released. This is even more visible higher in frequency where the driver starts to have a steeper natural rolloff. Do the same thing for a metal cone anywhere under it's breakup node and you will find the reproduced waveform closer to the original. That statement makes metal cones sound vastly superior, yet some folks still prefer softer cone materials.

Everything else being equal, (motor, frame, surround, spider, voice coil, cone geometry, etc) a metal cone will have a more accurate waveform reproduction at a given frequency, but will have a breakup node resulting in a peak in the frequency response. A poly cone will have no breakup node, but will have the information loss resulting from energy storage mentioned above. A frequency peak is just as much considered a form of distortion as information loss, but there is a difference: A frequency peak can be corrected with the right filter components, but information loss can't.

Simply put, a metal cone maintains pure piston movement much higher in frequency than a poly cone. In fact, some poorly designed poly drivers with curvilinear cones have such bad hysteresis that they don't have pure piston movement at any frequency. Rest assured however that well designed poly cone drivers have optimized geometry and are designed with materials science in mind.

The frequency at which a speaker begins to lose pistonic movement depends completely on it's geometrical stiffness and material parameters. It's generally misunderstood that there's more to it than just the diameter of the cone. This article however is only in relation to the material parameters. We'll talk about the geometrical stiffness issues some other day.

The key to this article is to explain why people have a preference. Reasons that some people prefer poly cones can be broken down into two main points. 1)Poly cones are easier to cross over. No harsh breakup node to deal with. There are even a few cases where a poly cone low pass crossover can simply consist of a single inductor. 2)Some music simply sounds better when reproduced through softer cones.

#2 is the key. How can music sound better when it is distorted? Well, when the original recording is poor, a metal cone isn't going to do much to conceal the distortion. Sharp abnormalities in the waveform come through loud and clear with a metal cone. Also, some amplified instruments introduce their own distortion which is all too audible and fatiguing unless we have a soft cone to "round the edges" in the waveform.

A word about the phrase "metal sound". Some metal drivers have been accused of having a metal sound. Most often, this comes about from poorly designed crossovers that do not address the breakup node. Sometimes, "metal sound" might come from drivers that seem properly filtered but in reality are crossed over too high. A breakup node can be notched out, but the 2nd and 3rd harmonics can't. If the intensity of a metal cone's breakup node is very high, a crossover point above a point 2 octaves below the breakup node will make the 2nd and 3rd harmonic distortion too audible. Other than that, metal cones can simply be described as detailed or accurate, sometimes *too* detailed or accurate for a person's taste.

There you have it. Aside from the fear of misunderstood crossovers, the kind of cone material you prefer is probably more influenced by the type of music you listen to than anything else. High distortion amplified instruments need soft cones while better recorded acoustic instruments will sound more lifelike with stiff coned drivers. Summed up even more, rock recordings need poly, classical or jazz recordings need metal, and those who listen to a wide variety of music may do well to chose one of the composite cones.

It's hard to generalize, as every material has variations in stiffness. For example, polypropylene can be formulated to be stiff and fragile, while some metal cones can be thinner or use an exponential profile to dissipate breakup nodes. I can however name a couple of common drivers representing the norm: a Vifa P17 poly cone or a Seas L17 aluminum cone. No two drivers of similar size could be further apart in the way they sound.

Personally, I prefer metal or other stiff cone materials as it suits my music tastes and I generally do ok on the crossovers that deal with breakup nodes."

dont forget that in a car we have a lot of highly reflective materials close to the radiation of our mid and treble drivers. Maybe a softer material would be preferred by some people for this very reason.

are carbon fibre cones on the comeback???

i have an old orion NT series recone kit and i have a 4year old set of speakers that use the audax carbon fibre midrange (they really do sound excellent and the deisgner uses 24db/oct to reduce cone breakup nodes).

also remember kiddys you cannot compare one speaker that is say carbon coned to another brand speaker that is metal coned. the difference's in sound are probly not the cone itself.. and i doubt that there is anyone here (maybe 1 or 2 ) that have heard the same speaker with different cone matirials.

seas car stuff use a notch filter to reduce the cone breakups and ragged frequency response in the upper mids above the x-over frequency.


so the x-over design for hard materials like metals require notch filters or high order slopes. notch filters will introduce more phase shift, and the higher slopes have different lobing patterns.