What type of material is best suited for a speaker cone, as i have read of different materials such as carbon fibre, paper and polypropelene being used.
Which material is the best for a speaker cone and which is probably the worst?
Also does the material used for the cone make a difference in the sound produced by the speaker and what type of material should surround the cone (is rubber better than foam etc.)
Thanks
Which material is the best for a speaker cone and which is probably the worst?
Also does the material used for the cone make a difference in the sound produced by the speaker and what type of material should surround the cone (is rubber better than foam etc.)
Thanks
You will never have 100% of the audio population agree on one best material, either in general or for specific types of drivers (i.e. tweeters or subwoofers).
I'll skip over the best/worst choices for cones, because you can check out this site: http://ldsg.snippets.org/appdx-b.php3 which will give you an overview of the different cone materials available. However, I think that crystalline diamond is the best tweeter diaphragm material currently available...
As for the surround, rubber lasts much longer than foam, and I think both can be engineered for any level of damping/stiffness. No idea about the different sound they impart.
I'll skip over the best/worst choices for cones, because you can check out this site: http://ldsg.snippets.org/appdx-b.php3 which will give you an overview of the different cone materials available. However, I think that crystalline diamond is the best tweeter diaphragm material currently available...
As for the surround, rubber lasts much longer than foam, and I think both can be engineered for any level of damping/stiffness. No idea about the different sound they impart.
I think foam has theoretical advantages, but it rots over time.
I disagree with many people about how long it takes to rot-I have seen foam speakers last near 20 years in good shape.
I think a lot depends on whether the speaker is placed near heat, or in the sun.
By comparison, rubber is forever, usually.
There are so many highly rated speakers which use rubber surrounds, that I would say that sonically, there is little difference.
Foam came out at a time when the normal speaker surround material was woven cloth. The "phenolic" treatment of this cloth, to prevent leaks, was similar to Elmer's Carpenter's glue! Those woven surrounds were known to be leaky. Foam is not leaky, so that was a big advantage at the time.
The rubber surrounds came out later. They are not leaky and have much of the flexibility of foam. But some manufacturers still prefer to go for the best combo of flexibility and airtightness, which is foam.
I lean toward rubber, if the driver is available. But I wouldn't reject foam categorically.
I disagree with many people about how long it takes to rot-I have seen foam speakers last near 20 years in good shape.
I think a lot depends on whether the speaker is placed near heat, or in the sun.
By comparison, rubber is forever, usually.
There are so many highly rated speakers which use rubber surrounds, that I would say that sonically, there is little difference.
Foam came out at a time when the normal speaker surround material was woven cloth. The "phenolic" treatment of this cloth, to prevent leaks, was similar to Elmer's Carpenter's glue! Those woven surrounds were known to be leaky. Foam is not leaky, so that was a big advantage at the time.
The rubber surrounds came out later. They are not leaky and have much of the flexibility of foam. But some manufacturers still prefer to go for the best combo of flexibility and airtightness, which is foam.
I lean toward rubber, if the driver is available. But I wouldn't reject foam categorically.
For cones, in general paper offers the best stiffness to weight ratio, especially when also considering price. But speaker building is a game of compromises. So it might be best in a design to compromise on one aspect to gain in another by using a more exotic material.
As for the surrounds, foam seems to be the best choice for subwoofers. This is because of a much better stiffness to weight ratio. Rubber has a problem of puckering, and to get rid of this you have to make it thick. This means added weight. Also, with modern treatments foam lasts much longer than rubber. This is because rubber tends to stiffen up over time, thereby effecting the performance of the driver.
Again, this is all general. The actual better choice for a given design will depend on the design goals. That is why you can never have a "best in all situations" answer.
Steven Kephart
Adire Audio
As for the surrounds, foam seems to be the best choice for subwoofers. This is because of a much better stiffness to weight ratio. Rubber has a problem of puckering, and to get rid of this you have to make it thick. This means added weight. Also, with modern treatments foam lasts much longer than rubber. This is because rubber tends to stiffen up over time, thereby effecting the performance of the driver.
Again, this is all general. The actual better choice for a given design will depend on the design goals. That is why you can never have a "best in all situations" answer.
Steven Kephart
Adire Audio
Pan said:
Theese days synthetic rubber is a very reliable product. I would believe that even under the worst thinkable circumstances (heat and sunlight), such a material would not change any during 25 years. The carbon percentage used today is so high that you can allmost dismiss the uv issue.
Magura
reply
How about cloth[plasticised linen cloth sometimes] surrounds as used on pa speakers.
These are very tough.Although someone gave me some old Gauss pa speakers with white die cast aluminium frame and cloth surround;where both the cloth surround and cone had fallen apart due to years of use in direct sunlight.
I got them reconed now are are lovely pa speakers!
And a pic of the lovely Gauss too!
How about cloth[plasticised linen cloth sometimes] surrounds as used on pa speakers.
These are very tough.Although someone gave me some old Gauss pa speakers with white die cast aluminium frame and cloth surround;where both the cloth surround and cone had fallen apart due to years of use in direct sunlight.
I got them reconed now are are lovely pa speakers!
And a pic of the lovely Gauss too!
Attachments
the_wonderchild said:
I think the Eton carbon fibre or kevlar not sure which and inbetween honeycomb shape has the best strength stiffness per weight, that's why I chose them. The kevlar or carbon fibre is not the issue it's the honeycomb that attracted me, although just of-the-cuff I would say carbon fiber is slightly stronger stiffer than kevlar. I haven't listened to many speakers, but I try to judge based on what seems logically to be the best material(s).
I would think wood fiber or paper cones would have the best internal damping or maybe polypropolene. I don't know though? Or aerogel, I don't even know what that is? I know which cone should be have the best stiffness to weight or the least the best strength to weight ratio (which I would imagine it not that critical unless you going to be kicking your speakers). I would imagine ceramic cones are stiffer than carbon fiber honeycomb sandwhich cone, but then carbon fiber honeycomb can be made a lot thicker than ceranics, which of course is much stiffer. Twice the thickness about 8 times the stiffness (incase you didn't know). So a lot comes into play. Wood fiber cone might sound the most natural, cause it comes from the ground man (to quote some marijuana advocates), but I can't give I rational reason, just like those marijuana advocates.
I read that article some one suggested. Go with Diamond. If your speakers don't sound good you can wear them around your neck
Diamond is stiffer than carbon fibre, but the honeycomb has air (which is very light last I checked) pockets between two surfaces. Also can be made for woofers (I'm guessing here) four times as thick as diamond for the same weight, that's about 64 times (althought it's probalby less cause of the air spaces, it's not solid all the way through) as stiff as diamond if diamond had the same stiffness. I don't know how much stiffer diamond actually is than the stiffest carbon fiber. But if it's like a factor of five or ten, than the carbon fiber honeycomb sandwhich might be stiffer for it's weight/shape. How bout a diamond honeycomb sandwhich?
Best??!! hahaha. There is no best. As many opinions as there are DIY'ers...
Anyway, here's mine:
Woofer- sandwich, like the focal W type. Makes more sense than high tech material in low tech application. Metal can be OK - like the seas - but efficiency is too low IMO for true fidelity, and they require high order crossovers. Or paper.
Midrange:
Paper, coated with something besides plastic
HF:
aluminum or alum/mag, or a good paper cone tweeter if you can find one...
YMMV.... and execution (cabinet, crossover, etc) is everything.
GB
Anyway, here's mine:
Woofer- sandwich, like the focal W type. Makes more sense than high tech material in low tech application. Metal can be OK - like the seas - but efficiency is too low IMO for true fidelity, and they require high order crossovers. Or paper.
Midrange:
Paper, coated with something besides plastic
HF:
aluminum or alum/mag, or a good paper cone tweeter if you can find one...
YMMV.... and execution (cabinet, crossover, etc) is everything.
GB
Re: reply
Plasticized cloth is rarely used on home or car speakers. PA speakers have different applications than home speakers.
For one thing, PA speakers are built to be driven into their nonlinear range very, very often. If you take a look at the linear Xmax of a most PA speakers, you will see that it is small compared to home speakers of the same size. Fifteen inch woofers with Xmaxes of 4 mm-you won't usually find that on home speakers, but you will with PA speakers.
The reason for that is that PA speakers make their voice coil winding small, so that there are a lot of turns in the magnetic gap at once. This gives the speaker a lot of force, therefore high sensitivity, but not much linear Xmax. However, PA speakers compensate by making tough spiders and surrounds that can take being driven well past the linear Xmax.
So the platicized cloth probably does a great job of letting the speaker be driven hard past it's linear Xmax, but perhaps not so good a job at operating so well within the linear Xmax as other surround types. that is why it is not usually found on home speakers.
Incidentally, there are some PA speakers that combine pretty long linear excursions and high sensitivity. Consider that for a speaker of 10 inches or above, 6 mm woould be considered a decent excursion. 12 mm or more is considered super long excursion for home speakers. The following PA woofers offer excursions not only longer than most PA speakers, but longer than the average home woofer as well:
McCauley 6242: 10 mm
Volt RV4504: 10 mm
Eminence KiloMax 15 in: 8mm
Eminence Kilomax 18 in: 10 mm
So some speakers do manage to combine high linear Xmax with the necessary high efficiency, (over 95 dB @ 1W/1M), of a PA speaker.
Bull said:
Plasticized cloth is rarely used on home or car speakers. PA speakers have different applications than home speakers.
For one thing, PA speakers are built to be driven into their nonlinear range very, very often. If you take a look at the linear Xmax of a most PA speakers, you will see that it is small compared to home speakers of the same size. Fifteen inch woofers with Xmaxes of 4 mm-you won't usually find that on home speakers, but you will with PA speakers.
The reason for that is that PA speakers make their voice coil winding small, so that there are a lot of turns in the magnetic gap at once. This gives the speaker a lot of force, therefore high sensitivity, but not much linear Xmax. However, PA speakers compensate by making tough spiders and surrounds that can take being driven well past the linear Xmax.
So the platicized cloth probably does a great job of letting the speaker be driven hard past it's linear Xmax, but perhaps not so good a job at operating so well within the linear Xmax as other surround types. that is why it is not usually found on home speakers.
Incidentally, there are some PA speakers that combine pretty long linear excursions and high sensitivity. Consider that for a speaker of 10 inches or above, 6 mm woould be considered a decent excursion. 12 mm or more is considered super long excursion for home speakers. The following PA woofers offer excursions not only longer than most PA speakers, but longer than the average home woofer as well:
McCauley 6242: 10 mm
Volt RV4504: 10 mm
Eminence KiloMax 15 in: 8mm
Eminence Kilomax 18 in: 10 mm
So some speakers do manage to combine high linear Xmax with the necessary high efficiency, (over 95 dB @ 1W/1M), of a PA speaker.
Whatever the cone material, there are 2 important properties to keep in mind: stiffness and resonance damping. To vibrate as one piece the cone material should be stiff and have an optimized "cone" or "dome" shape so that the vibrations travel extremely quickly across the whole area of the material. Inevitably, some vibrations will have a frequency that's too high for the whole cone to move as one piece, so the resulting partial oscillations / resonances have to be damped somehow. The surround material should help and a softer cone material will help too. However, in this regard a soft cone material such as paper can be its own worst enemy because the softer the material, the lower the frequency at which partial oscillations start in the first place.
Eton: kevlar|honeycomb|kevlar sandwich for stiffness, and a paper-mache dustcap to absorb stray vibrations.
Accuton: inverted ceramic dome for stiffness, and relies on electrical filtering to eliminate the resonant peak.
Seas: aluminium or magnesium cone for stiffness, similar to Accuton, Alcone and Visaton.
Jordan: extremely thin aluminium cone, and well-controlled partial oscillations are progressively absorbed as they travel away from the voice-coil. Same concept as Manger speakers, but different design.
Eton: kevlar|honeycomb|kevlar sandwich for stiffness, and a paper-mache dustcap to absorb stray vibrations.
Accuton: inverted ceramic dome for stiffness, and relies on electrical filtering to eliminate the resonant peak.
Seas: aluminium or magnesium cone for stiffness, similar to Accuton, Alcone and Visaton.
Jordan: extremely thin aluminium cone, and well-controlled partial oscillations are progressively absorbed as they travel away from the voice-coil. Same concept as Manger speakers, but different design.
Magura said:
Theese days synthetic rubber is a very reliable product. I would believe that even under the worst thinkable circumstances (heat and sunlight), such a material would not change any during 25 years. The carbon percentage used today is so high that you can allmost dismiss the uv issue.
Magura
I have just bought some Seas 17 cm drivers on ebay (the variety with the semi-clear PP membrane and soft dust cap) which have a rubber surround (SR 138/1, most likely made by Kurt Müller). The seller said the drivers were about 11 years old and the surrounds were a bit porous.
Well, they top side was riddled with small cracks and had turned brownish locally. The down side looked ok but was also harder than usual. The stiffness of the whole surround (when pressing down the cone) was about 3x more than usual.
Re: Re: reply
TAD's Model-1 uses accordion surrounds on their woofers. I don't exactly know what material those surrounds are made of, but most probably cloth. I had once heard these being demoed. The demo guy had told that the reason accordion surrounds are not used much was because it was hard to get them right, but once gotten right they were superior to half roll surrounds. I wouldn't pay much attention to this sales guys explanation, but it looks like TAD didn't make any sacrifices while designing this speaker. So if they had thought a half roll surround would have been better they would have used it, it is a no cost object design. BTW, I like their cone material choices, I would probably go with Eton's kevlar hexacone on the woofers, rather than their woven kevlar foam sandwichs but they should perform pretty close. The mid and tweeter is Berrylium. It will ring but at a very high frequency, because of its very high speed of sound. I would like to get a hold of to their mid/tweeter coax driver, but don't think it is available for sale. Even if it were, it would have been too expensive for my wallet.
http://www.tadhomeaudio.com/gallery.html
kelticwizard said:
TAD's Model-1 uses accordion surrounds on their woofers. I don't exactly know what material those surrounds are made of, but most probably cloth. I had once heard these being demoed. The demo guy had told that the reason accordion surrounds are not used much was because it was hard to get them right, but once gotten right they were superior to half roll surrounds. I wouldn't pay much attention to this sales guys explanation, but it looks like TAD didn't make any sacrifices while designing this speaker. So if they had thought a half roll surround would have been better they would have used it, it is a no cost object design. BTW, I like their cone material choices, I would probably go with Eton's kevlar hexacone on the woofers, rather than their woven kevlar foam sandwichs but they should perform pretty close. The mid and tweeter is Berrylium. It will ring but at a very high frequency, because of its very high speed of sound. I would like to get a hold of to their mid/tweeter coax driver, but don't think it is available for sale. Even if it were, it would have been too expensive for my wallet.
An externally hosted image should be here but it was not working when we last tested it.
http://www.tadhomeaudio.com/gallery.html
In the end you have to evaluate a driver as a whole, the cone & surround materials are just a piece of the puzzle.
That said, most of the drivers i play with are paper (and usually end up being treated paper), but i also have aluminum, poly, and various plastics.
A very unappreciated device, the well done paper cone tweeter. I have a very nice pair of alnico peerless sitting here on my desk...
dave
That said, most of the drivers i play with are paper (and usually end up being treated paper), but i also have aluminum, poly, and various plastics.
A very unappreciated device, the well done paper cone tweeter. I have a very nice pair of alnico peerless sitting here on my desk...
dave
If you can find the book written by Jordan, (called Loudspeakers, from memory - what else) its well worth wading through. Much maths, but that can be skipped.
He started off with paper cones while designing at Goodmans, producing excellent full range paper units, ( and I believe an experimental electrostatic at the same time Peter Walker brought out his Quad), before going off on his own and producing aluminium foil full range units that evolved into his present units, (and also indirectly, the Bandor units). He also used titanium at one stage.
Basically his reasoning was that full range (as far as possible) was the best approach, and no cone material could be totally stiff, but must break up. In fact this was essential to achieve good results, with an effectively shrinking cone area as the frequency increased. The book plus the various Wireless World articles he wrote explain this well.
The need to have smaller cone area with increasing frequency had been accepted for a long time, either using multiple drivers, or by experimenting with the cone of a large driver to acheive the same result. Jordan was the first that I am aware to put maths to the problem, with a single homogenious material, but others had pioneered wide range single driver units, (including I think, Voigt). The biggest problem earlier was the lack of good glues, restricting materials that could be used, but wartime developement improved matters.
In the nineteen fifties in UK many speakers were full range, up to about 15K. A falling HF response was desireable to reduce record hiss. To get good bass, typically a 12 inch paper cone, (although GEC had a steel unit), was used, with various devices to give good mid and treble performance. For example the whizzer cone used by Philips, Wharfdale, Goodmans and others, typically paper but bakalite and other hard materials were also used. Lowther using cambric is a legacy of that time, now much improved. Another using cambric stiffened with varnish was Duode, who built a logrithmic spiral into the cone to give the controlled breakup necessary. He also used an aluminium coil former with a latex rubber compliance between former and winding to produce a lighter driven cone and hence better HF. Hartley Turner did the same, but with a paper cone, also cut part way between apex and surround, and rejoined with a compliant material. This effectively gave a central tweeter driven from the same voice coil. A frequency response of 40 to 15Kz within plus/minus 5 db was claimed.
Some later units used layered cones, stiffening the centre, sometimes with aluminium.
The sound quality of the best units from this period is still very acceptable, although they need large cabinets to give good bass, and the highest treble is missing.
For two and three way speakers, development concentrated mainly on paper for the bass/mid drivers, but a wide range of materials were used for tweeters, including paper, cambric, metals and various plastics. The introduction of poly and other plastics, giving manufacturing advantages despite their poorer sound, plus the need to reach the higher frequencies effectively killed the old HiFi full range units, except for Jorden, (Al), Lowther,(cloth), Foster, (paper), and a very few others, which had designed for best treble at the expense of bass extension.
Paper with its inherent self damping, is probabily still the easiest to get acceptable wide range results with. Hence still its use in such widely diverse full range applications as cheap transistors and the high quality CSS WR125
With a more limited frequency range to be covered by each cone, manufacturers moved away from the approach of a controlled or damped break-up and tried to produce infinitely stiff cones, (an impossibility of course), using new and old materials such as metal, carbon fibre, kevlar etc. Properly treated paper can still hold its own, as shown by its use in some very expensive drivers. Excellent results can be achieved by any of these in the hands of a good designer, but at times you wonder if the material is chosen simply to give a marketing point.
Each material has its own characteristic sound, which is why personal preference is still the main controlling factor in choice. As a very broad generalisation, ( and please don't flame me for this), stiffer cones produce transients better, but can be harsh, but softer cones smooth the music and can be more pleasing. to the ear. The one in the middle ground, and the one still liked by most listeners is paper, with its internal dampening, even though it may not be the most accurate and lifelike.
Cone surrounds have also gone full circle. Some early units used rubber or cloth single roll, before moving to mulitple corrogation, then foam, then back to a single roll, but at least with longer lasting materials.
So back to the original question re cone material, there is no perfect material. Each, in the proper application, can be as good as any other, just with a different set of faults and problems. The more modern ones are not necessarily better than the older ones.
None sound like the real thing.
He started off with paper cones while designing at Goodmans, producing excellent full range paper units, ( and I believe an experimental electrostatic at the same time Peter Walker brought out his Quad), before going off on his own and producing aluminium foil full range units that evolved into his present units, (and also indirectly, the Bandor units). He also used titanium at one stage.
Basically his reasoning was that full range (as far as possible) was the best approach, and no cone material could be totally stiff, but must break up. In fact this was essential to achieve good results, with an effectively shrinking cone area as the frequency increased. The book plus the various Wireless World articles he wrote explain this well.
The need to have smaller cone area with increasing frequency had been accepted for a long time, either using multiple drivers, or by experimenting with the cone of a large driver to acheive the same result. Jordan was the first that I am aware to put maths to the problem, with a single homogenious material, but others had pioneered wide range single driver units, (including I think, Voigt). The biggest problem earlier was the lack of good glues, restricting materials that could be used, but wartime developement improved matters.
In the nineteen fifties in UK many speakers were full range, up to about 15K. A falling HF response was desireable to reduce record hiss. To get good bass, typically a 12 inch paper cone, (although GEC had a steel unit), was used, with various devices to give good mid and treble performance. For example the whizzer cone used by Philips, Wharfdale, Goodmans and others, typically paper but bakalite and other hard materials were also used. Lowther using cambric is a legacy of that time, now much improved. Another using cambric stiffened with varnish was Duode, who built a logrithmic spiral into the cone to give the controlled breakup necessary. He also used an aluminium coil former with a latex rubber compliance between former and winding to produce a lighter driven cone and hence better HF. Hartley Turner did the same, but with a paper cone, also cut part way between apex and surround, and rejoined with a compliant material. This effectively gave a central tweeter driven from the same voice coil. A frequency response of 40 to 15Kz within plus/minus 5 db was claimed.
Some later units used layered cones, stiffening the centre, sometimes with aluminium.
The sound quality of the best units from this period is still very acceptable, although they need large cabinets to give good bass, and the highest treble is missing.
For two and three way speakers, development concentrated mainly on paper for the bass/mid drivers, but a wide range of materials were used for tweeters, including paper, cambric, metals and various plastics. The introduction of poly and other plastics, giving manufacturing advantages despite their poorer sound, plus the need to reach the higher frequencies effectively killed the old HiFi full range units, except for Jorden, (Al), Lowther,(cloth), Foster, (paper), and a very few others, which had designed for best treble at the expense of bass extension.
Paper with its inherent self damping, is probabily still the easiest to get acceptable wide range results with. Hence still its use in such widely diverse full range applications as cheap transistors and the high quality CSS WR125
With a more limited frequency range to be covered by each cone, manufacturers moved away from the approach of a controlled or damped break-up and tried to produce infinitely stiff cones, (an impossibility of course), using new and old materials such as metal, carbon fibre, kevlar etc. Properly treated paper can still hold its own, as shown by its use in some very expensive drivers. Excellent results can be achieved by any of these in the hands of a good designer, but at times you wonder if the material is chosen simply to give a marketing point.
Each material has its own characteristic sound, which is why personal preference is still the main controlling factor in choice. As a very broad generalisation, ( and please don't flame me for this), stiffer cones produce transients better, but can be harsh, but softer cones smooth the music and can be more pleasing. to the ear. The one in the middle ground, and the one still liked by most listeners is paper, with its internal dampening, even though it may not be the most accurate and lifelike.
Cone surrounds have also gone full circle. Some early units used rubber or cloth single roll, before moving to mulitple corrogation, then foam, then back to a single roll, but at least with longer lasting materials.
So back to the original question re cone material, there is no perfect material. Each, in the proper application, can be as good as any other, just with a different set of faults and problems. The more modern ones are not necessarily better than the older ones.
None sound like the real thing.
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