Carbon Fibre Speaker Cones???

[Sliced Bread]

http://www.whathifi.com/news/pagani-huayra-sonus-faber-sound-system-to-be-demonstrated-at-munich-high-end-show

After reading the above article, I started wondering why more speakers don't use Carbon Fiber mid / bass drivers.

Carbon fibre is lught, stiff and not as expensive as it once was. I would have thought it would be ideal.

Anyone know why?

 

[BigH]

Its probably expensive. I know CF in tripods and I know when its cold like -20C it can shatter so I guess there maybe problems when temperature changes. I know Kevlar is used in some speakers now so maybe CF will become more common.

Here is something about CF: "The next generation or rigid-cone drivers were the Japanese carbon-fiber units, which made their first appearance in the pro studio monitor (prosound) 12" TAD units with very high efficiencies and very high prices (around $300 each in 1980). Carbon fiber prices have now dropped, and Vifa, Audax, and Scan-Speak make good examples of this type of driver. The Japanese make lots more of them, having pioneered the technology, but they are very difficult to obtain if you are a non-Japanese small-run specialist manufacturer.

These drivers have true piston action, outstanding bass and midbass response (the best I have ever heard), but also have a characteristic double-peak region at the top of the working range. Unfortunately, these peaks are grossly audible in most carbon-fiber drivers, and worse, cannot be removed by a notch filter tuned between the two peaks; it requires two notch filters to control the peaks, or a low crossover with a very sharp rolloff (24dB/octave) to remove them from audibility.

Although I very much dislike drivers that require filters as complex as this (after doing the TLM-200, I vowed never again to design a 57-component crossover), I must admit that carbon fiber woofers are the only direct radiators where I've actually felt tactile bass."

 

[matt49]

Proac make a speaker with CF bass and mid drivers.

http://www.proac-loudspeakers.com/html_files/Speakers.php?Range=CarbonPro&Speaker=CarbonPro8

The Carbon Pro 8s are £25K a pair ... as BigH says, 'It's probably expensive'.

 

[DocG]

Anthony Gallo uses carbon fibre drivers in his Reference range. The Strada's cost $2000 a pair, which sounds reasonable for a pair of high end (though not full range) speakers.

 

[Joshuamessenger]

REL use them in there subs so they must be strong below 50Hz

 

[oldric_naubhoff]

I still think a stretched sheet of mylar will be a better solution against even the best materials of which dynamic woofers can be made. because panel mylar driver is much lighter so a faster response is obtainable. because panel driver will almost always be much bigger than most dynamic drivers you get lower THD over entire audioband and especially bass. and because panel mylar driver will be used in ESLs or quasi-ribbon designs you don't have to worry about any back EMF from woofer coil.

 

[AEJim]

As BigH picked up on - there are pro's and cons to all drive unit materials. There are many variables such as stiffness, weight, break-up points, damping and cost to consider with drivers.

Paper is still one of the best cone materials in many respects, self-damping, gradual break-up, stiff, light and cheap! We use Aluminium for its more pistonic nature (higher stiffness), coil heat transferrence (lower distortion) and higher break-up point - but the trade-off is heavier weight and the higher break-up being more severe than the gradual break-up with paper, which is countered through damping glues and surround materials etc.

All materials I've experimented with have their own characteristics which you have to learn to work with and choose those with strengths you prefer and weaknesses you can counter, as well as cost considerations for the product in which they'll be used. This is part of the reason there is so much choice and variation on the fairly standard theme of a dynamic cone driven speaker!

 

[hoopsontoast]

I still think a stretched sheet of mylar will be a better solution against even the best materials of which dynamic woofers can be made. because panel mylar driver is much lighter so a faster response is obtainable. because panel driver will almost always be much bigger than most dynamic drivers you get lower THD over entire audioband and especially bass. and because panel mylar driver will be used in ESLs or quasi-ribbon designs you don't have to worry about any back EMF from woofer coil.

I would agree But its not always possible to get Open Baffle / Di-Pole speakers in to a lot of domestic rooms.

Its probably expensive. I know CF in tripods and I know when its cold like -20C it can shatter so I guess there maybe problems when temperature changes. I know Kevlar is used in some speakers now so maybe CF will become more common.

Here is something about CF: "The next generation or rigid-cone drivers were the Japanese carbon-fiber units, which made their first appearance in the pro studio monitor (prosound) 12" TAD units with very high efficiencies and very high prices (around $300 each in 1980). Carbon fiber prices have now dropped, and Vifa, Audax, and Scan-Speak make good examples of this type of driver. The Japanese make lots more of them, having pioneered the technology, but they are very difficult to obtain if you are a non-Japanese small-run specialist manufacturer.

These drivers have true piston action, outstanding bass and midbass response (the best I have ever heard), but also have a characteristic double-peak region at the top of the working range. Unfortunately, these peaks are grossly audible in most carbon-fiber drivers, and worse, cannot be removed by a notch filter tuned between the two peaks; it requires two notch filters to control the peaks, or a low crossover with a very sharp rolloff (24dB/octave) to remove them from audibility.

Although I very much dislike drivers that require filters as complex as this (after doing the TLM-200, I vowed never again to design a 57-component crossover), I must admit that carbon fiber woofers are the only direct radiators where I've actually felt tactile bass."

Yes this is the big problem with very stiff cones like Metal, Carbon-Fibre and other exotic based cones, they break up really badly at the top end of their range and require very complex crossovers or a lot of DSP. Paper and some Plastic based cones may not be as pistonic but tend to have a nice even roll off that makes very simple to design crossovers for.

Personally, I would tend to prefer lightweight, high efficiency paper wider range drivers like the Rega ones for example.

 

[DocG]

Yes this is the big problem with very stiff cones like Metal, Carbon-Fibre and other exotic based cones, they break up really badly at the top end of their range and require very complex crossovers or a lot of DSP. Paper and some Plastic based cones may not be as pistonic but tend to have a nice even roll off that makes very simple to design crossovers for.

For the Strada, Anthony Gallo seems to have managed to just avoid the need for a crossover. The combination of these light CF woofers with a ribbon tweeter, without XO and without a box, looks really appealing. 8) It's just so bl°°dy difficult to find a dealer where they can be auditioned... :wall:

 

[hoopsontoast]

Yes this is the big problem with very stiff cones like Metal, Carbon-Fibre and other exotic based cones, they break up really badly at the top end of their range and require very complex crossovers or a lot of DSP. Paper and some Plastic based cones may not be as pistonic but tend to have a nice even roll off that makes very simple to design crossovers for.

For the Strada, Anthony Gallo seems to have managed to just avoid the need for a crossover. The combination of these light CF woofers with a ribbon tweeter, without XO and without a box, looks really appealing. 8) It's just so bl°°dy difficult to find a dealer where they can be auditioned... :wall:

Interesting, they do seem to manage without a crossover on the mid-bass drivers, I wonder how that works with lobing higher up the FR range and BSC at the bottom, unless its passively equalised by the bass drivers response in what looks like a very small sealed enclosure.

Never heard any but would be interesting to at some point.

 

[Sliced Bread]

Thanks for the info....Lots of facinating answers here. This is a side of HiFi that I know little about

One nooby question: What do you mean by breakup? Is that when the cone is at a volume or frequesncy that's beyond it's limit. So a fast break up would be a speaker driver that quickly starts distorting at when it reaches a threashold?

 

[oldric_naubhoff]

What do you mean by breakup? Is that when the cone is at (...) frequency that's beyond it's limit. So a fast break up would be a speaker driver that....

... has low upper frequency limit (for a woofer).

 

[oldric_naubhoff]

I still think a stretched sheet of mylar will be a better solution against even the best materials of which dynamic woofers can be made. because panel mylar driver is much lighter so a faster response is obtainable. because panel driver will almost always be much bigger than most dynamic drivers you get lower THD over entire audioband and especially bass. and because panel mylar driver will be used in ESLs or quasi-ribbon designs you don't have to worry about any back EMF from woofer coil.

forgotten to add; no problems with any break modes (but in all fairness there may be problems with so called drumhead resonances, but those are far more easily managed then break modes).

 

[Sliced Bread]

What do you mean by breakup? Is that when the cone is at (...) frequency that's beyond it's limit. So a fast break up would be a speaker driver that....

... has low upper frequency limit (for a woofer).

Ah, gotcha!

Thanks