|
|
Post by leonski on Aug 29, 2018 2:06:07 GMT -5
We have been hearing about Graphene for a decade plus by now. Not many real applications though one I've been hearing about is directly related to speakers.
Originally I'd hoped that large graphene sheets could be fabricated into Planar Speakers. The immense strength meant incredible LIGHTWEIGHT drivers of high speed. This would improve the sensitivity
against 'conventional' planar speakers and have several other implications as well. I was hoping for a Graphene Ribbon and that might still happen.
But what I saw was Graphene as a conductive INK. Able to be printed onto a substrate which than can resist heat, folding and perhaps even some or many solvents.
Right now, a popular tweeter is the folded, HEIL design. EMO used it. RadioShack used one and I think it was ESS that used one as well. the 'Heil Air Motion Transformer' was and IS a pretty good tweeter.
But imagine reducing the moving mass yet further. This would improve sensitivity and probably result in HF response so high it was be flat to the limits of human hearing. Even an infant.
Conductive INK also brings my panels one step closer. Just print the wire pattern on to a substrate. You'd eliminate the weight of the wire and adhesives. Higher HF limit and again, higher sensitivity.
Same goes for printing a wire on a substrate for a RIBBON tweeter. With such a driver 'up down', it has little coupling to ceiling or floor but excellent horizontal dispersion. Win Win when you can extend
the frequency response, increase driver 'speed' and sensitivity all in one shot.
All without higher strength and $$$ Neo Magnets.
I hope I see a demo of this in the near future.
|
|
klinemj
Emo VIPs 
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 29, 2018 9:01:54 GMT -5
It will be fun to see what new materials bring to speakers. I've become a huge fan of ribbon tweeters and planar speakers overall. To imagine them getting better...will be cool and I would want to hear it. What would be really cool would be a technology to make massive movements required in bass drivers with a fraction of the mass of today's magnet-based systems...very low power could make amazing bass.
Mark
|
|
|
|
Post by leonski on Aug 29, 2018 14:47:16 GMT -5
A couple paths to higher sensitivity. Lowering mass without effecting stiffness is part of the equation. First? STronger Magnets. Magnepan uses something about the range of a refrigerator magnet. Using Neo would add to sensitivity of the speaker as well as Cost / Complexity of assembly and worker safety problems. That stuff is nasty to work with and you can hurt yourself in a 'magnet pinch'. It's also brittle and requires careful handling. Second? Decreased distance between magnet and coil. Making a smaller magnet 'gap' helps sensitivity. But again the trade offs involve higher expense, handling of assembly and design issues. You can also get the magnet and coil TOO CLOSE and in the case of planar speakers, limit dynamic range. In the FAR DISTANT future? I'd have a speaker with a room temperature Super Conductor Field Coil Magnet, not a permanent magnet. Field Coil speakers are available and can sound good. www.dagogo.com/line-magnetic-audio-lm-755i-field-coil-speaker-review/ |
|
klinemj
Emo VIPs
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 29, 2018 21:37:13 GMT -5
While I am no expert in speaker sub-system design, I agree that strong magnets and closer tolerances would help. But, for true breakthrough - something totally different is needed. As an example, all sub drivers that make very low bass in small sizes that I know of have a speaker cone connected to a voice coil that is moved in a magnetic field to cause the cone to move and make bass. In that realm, the power of the magnet and mass of the moving parts (voice coil + cone mass) + ability to cool the system drive power output and reliability.
And the connection between the cone/voice coil and magnet are pretty much the same.
What if it were radically different? What if the magnet power to voice coil/cone mass ratio could be RADICALLY changed? This would allow high power with low cooling needs, thus reliability? There are some fundamental physics that apply to enable this. I'd be happy to work with folks like Emotiva or others to develop such options. I have some credible ideas. While I would love to share them here, that would make my ideas not patentable...and therefore, less valuable. I'd be happy to elaborate...for a fee. So, don't expect me to share more. (That's what my consulting company is for...)
Mark
|
|
|
|
Post by leonski on Aug 30, 2018 1:16:56 GMT -5
Speakers are VERY low efficiency. About 5% tops, would be well NORTH of 105db 1 watt. The rest is HEAT. The way to make your suggestion work would be to have extreme efficiency so you'd only NEED 40 watts or 50 watts MAX. You can compute resistance losses by starting out with figuring the Voic Coil had maybe 4ohms DC resistance and work back from there. Current material limits mean a minimum weight to get the required stiffness in a cone. This in turn means a certain POWER to the 'motor'. Stronger magnets are just ONE avenue to higher sensitivity. Some of those 4" thru 6" or so SINGLE DRIVER systems use magnets which with the small desgned gap can reach 2 Tesla........These are all NEO magnets. These are LOWTHAR speakers. High $$$. www.lowtherloudspeakers.com/html/products.htmlthat's pretty strong. - I think in the old days of Big Box speakers, they used ALNICO magnets. |
|
klinemj
Emo VIPs
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 30, 2018 6:55:19 GMT -5
Speakers are VERY low efficiency. About 5% tops, would be well NORTH of 105db 1 watt. The rest is HEAT. The way to make your suggestion work would be to have extreme efficiency so you'd only NEED 40 watts or 50 watts MAX. You can compute resistance losses by starting out with figuring the Voic Coil had maybe 4ohms DC resistance and work back from there. Current material limits mean a minimum weight to get the required stiffness in a cone. This in turn means a certain POWER to the 'motor'. Stronger magnets are just ONE avenue to higher sensitivity. Some of those 4" thru 6" or so SINGLE DRIVER systems use magnets which with the small desgned gap can reach 2 Tesla........These are all NEO magnets. These are LOWTHAR speakers. High $$$. www.lowtherloudspeakers.com/html/products.htmlthat's pretty strong. - I think in the old days of Big Box speakers, they used ALNICO magnets. What I have in mind would indeed drive major efficiency gains. Far more than better magnets or just lower weight. Coupled with better magnets and lower weight would of course be best. Would love to elaborate...but... Mark |
|
KeithL
Administrator 
Posts: 9,938
|
Post by KeithL on Aug 30, 2018 8:51:51 GMT -5
In the really old days speakers had iron magnets - and sometimes electromagnets. Then they went to AlNiCo (aluminum, nickel, copper, cobalt, and iron); which were better but still had issues. After that ferrite became quite popular - and still is - because it offers a good combination of cost, strength, convenience, and permanence.
Then cobalt samarium was used for a while in some high end tweeters; it's very powerful, but still not as good as neodymium, and more epensive. Now the current high end material is neodymium - which is very powerful per weight. Neodymium is a "rare Earth" material, but isn't all that rare, and the cost is reasonable in large quantities.
A stronger magnet would certainly make for a more efficient speaker - and a stiffer lighter cone would be a benefit for midrange drivers. However, when it comes to woofers, simply making the cone stiffer and lighter isn't enough. When you put a bass driver in an enclosure it has a resonant frequency - which depends on the moving mass and the spring constant. And the spring is a combination of the spider, the surround, and the pressure of the air in the cabinet. If you make the cone very light then the resonant frequency goes up.... and we prefer it to remain low - outside the critical frequency range. You can reduce the resonance by making the suspension floppier - but, if you make it too soft, then the driver doesn't stay centered properly in its range.
And you can reduce the spring by making the cabinet bigger (that way, when the cone moves, it doesn't compress the air as much, so the air becomes a "softer spring"). However, the upshot is that, with subwoofers, and even woofers, you sometimes end up deliberately ADDING mass to the cone to get the other parameters where you want them.
We're already seeing carbon fiber used as a stiffening material in cones... and it has benefits. (And, yes, as a buzz-work we'll be seeing graphene used in that context.) However, it seems more likely that it will actually be more significant for the ability to use it in printed voice coils for planar and folder ribbon drivers, and in super-thin electrostatic diaphragms.
Speakers are VERY low efficiency. About 5% tops, would be well NORTH of 105db 1 watt. The rest is HEAT. The way to make your suggestion work would be to have extreme efficiency so you'd only NEED 40 watts or 50 watts MAX. You can compute resistance losses by starting out with figuring the Voic Coil had maybe 4ohms DC resistance and work back from there. Current material limits mean a minimum weight to get the required stiffness in a cone. This in turn means a certain POWER to the 'motor'. Stronger magnets are just ONE avenue to higher sensitivity. Some of those 4" thru 6" or so SINGLE DRIVER systems use magnets which with the small desgned gap can reach 2 Tesla........These are all NEO magnets. These are LOWTHAR speakers. High $$$. www.lowtherloudspeakers.com/html/products.htmlthat's pretty strong. - I think in the old days of Big Box speakers, they used ALNICO magnets. What I have in mind would indeed drive major efficiency gains. Far more than better magnets or just lower weight. Coupled with better magnets and lower weight would of course be best. Would love to elaborate...but... Mark |
|
klinemj
Emo VIPs
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 30, 2018 9:55:44 GMT -5
All true, however...none of what you say relates to the ideas I've been noodling around. Again - would love to share, but..."can't without a CDA, etc..."
Mark
|
|
|
|
Post by leonski on Aug 30, 2018 13:57:51 GMT -5
klinemj?
Would you like a copy of my personal MNDA?
I'll see if I can find it on my confuser(s)
|
|
|
|
Post by leonski on Aug 30, 2018 14:22:07 GMT -5
In the really old days speakers had iron magnets - and sometimes electromagnets. Then they went to AlNiCo (aluminum, nickel, copper, cobalt, and iron); which were better but still had issues. After that ferrite became quite popular - and still is - because it offers a good combination of cost, strength, convenience, and permanence.
Then cobalt samarium was used for a while in some high end tweeters; it's very powerful, but still not as good as neodymium, and more epensive. Now the current high end material is neodymium - which is very powerful per weight. Neodymium is a "rare Earth" material, but isn't all that rare, and the cost is reasonable in large quantities.
A stronger magnet would certainly make for a more efficient speaker - and a stiffer lighter cone would be a benefit for midrange drivers. However, when it comes to woofers, simply making the cone stiffer and lighter isn't enough. When you put a bass driver in an enclosure it has a resonant frequency - which depends on the moving mass and the spring constant. And the spring is a combination of the spider, the surround, and the pressure of the air in the cabinet. If you make the cone very light then the resonant frequency goes up.... and we prefer it to remain low - outside the critical frequency range. You can reduce the resonance by making the suspension floppier - but, if you make it too soft, then the driver doesn't stay centered properly in its range.
And you can reduce the spring by making the cabinet bigger (that way, when the cone moves, it doesn't compress the air as much, so the air becomes a "softer spring"). However, the upshot is that, with subwoofers, and even woofers, you sometimes end up deliberately ADDING mass to the cone to get the other parameters where you want them.
We're already seeing carbon fiber used as a stiffening material in cones... and it has benefits. (And, yes, as a buzz-work we'll be seeing graphene used in that context.) However, it seems more likely that it will actually be more significant for the ability to use it in printed voice coils for planar and folder ribbon drivers, and in super-thin electrostatic diaphragms.
What I have in mind would indeed drive major efficiency gains. Far more than better magnets or just lower weight. Coupled with better magnets and lower weight would of course be best. Would love to elaborate...but... Mark One big 'drive' (pardon the expression) to speakers is what in automotive terms would be HP to Weight Ratio. While higher mass, (per Keith, above) DOES have a lower resonant frequency, designers are up against both desired outcomes / costs but also material limits as well. You can't have an 'infinitely' stiff cone, for example. Or infinitely strong magnet structure. One disadvantage of NEO is that while it IS a 'rare Earth', it also is found in deposits with OTHER Rare Earths which make discrimination between them more difficult and costly. I read some time ago about the RE-Opening of a mine / diggings in the USA in which Rare Earths were found. In economically viable concentrations, given the new costs. However? China seems to be major in the current market and can turn the tap 'off' whenever they desire. And as a result can sort of dictate pricing. Rare Earths are all in the Lathanide Series in include a few other materials like Scandium and Yitirium. The last? I've seen mentioned as part of a formula for Superconductors. Telling the Lananide Series apart from one another is the problem. Adding to cost. Neo magnets are also much more difficult to handle. They are Brittle. And you haven't LIVED until you've PINCHED yourself between 2 Ultra Strong Magnets. They must be kept apart on the bench or the result is an expensive mess. Keith mentions 'electro magnets'. These are making a small and $$$ comeback and are billed as 'field coil' designs. I've heard one at a show and it was very good, indeed, and EXPENSIVE. But given the high sensitivity, you don't need more than maybe 100 watts to get evicted from the city in which you live. Maybe even 10 watts? Stuff like the 330$ Pass 'Amp Camp Amp' are popular for high sensitivity speakers. While you have many speakers available today, they still fall into 2 major 'camps'. High sensitivity are generally in large enclosures and the speakers are highly self-damped. Good for Tubes with low DF. The newer generation, started way back by stuff like the AR2 and AR3a (a dream speaker for me, at the time) and use the 'air spring' Keith mentions. These speakers generally like a High DF which means SS amps. I'm not sure of the State of The Art with Graphene. I see NO mention of 'sheets' which would be nice for some imaginable applicaitons. And I'm not sure of the other physical properties. How 'stretchy' is it? What is the measure of its electrical conductivity? Temp Limits of use? Does GLUE stick to it? Crazy Glue? Epoxy Glue? Elmers? I can think of several other questions about that stuff which going thru what's published may answer. But the stakes are high. Lots of stuff going on of which we are not aware. As usual? Stay Tuned |
|
klinemj
Emo VIPs
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 30, 2018 20:18:33 GMT -5
leonski In my work, I have looked into graphene for reasons unrelated to speakers. That was a few years ago, but a big challenge with it is that it's a bear to handle in a manufacturing environment due to its particle size. A company I was working with on it had developed a technique to put it into solution and use that to deposit it then cure it. They were depositing it on a range of materials including nonwovens (fabrics commonly used in products like diapers, feminine hygiene pads, wipes, car covers, etc.) The resulting fabrics were less flexible than the ingoing fabric but were very pliable/not brittle at all. That was more a function of the solution they'd deposited and cured. I was just looking up their electrical properties and they have some interesting properties...but not sure what would happen to those properties in the application process I mentioned. Mark
|
|
hemster
Global Moderator
Particle Manufacturer
...still listening... still watching
Posts: 51,920
|
Post by hemster on Aug 30, 2018 21:29:36 GMT -5
If you take a slice of graphene (like ruler thickness), you can literally slice an ice cube in half without using much downward pressure. Scientific explanation: graphene molecules trap and transmit the heat from your hands very efficiently. It's a neat party trick!  |
|
|
|
Post by leonski on Aug 30, 2018 23:55:53 GMT -5
Where do you source such a piece of Graphene? Graphite, yes. Graphene? I don't know.
As for Graphene when MIXED with some kind of solvent or other 'carrier'?
Figure something out for a 3d printer with a wide enough carriage to make planar or eventually-to-be-folded speaker diaphragms. Print on Mylar (1/2 mil? 1/4 mil?) or Kapton.
|
|
klinemj
Emo VIPs
Honorary Emofest Scribe
Posts: 14,744
|
Post by klinemj on Aug 31, 2018 8:34:30 GMT -5
Where do you source such a piece of Graphene? Graphite, yes. Graphene? I don't know. As for Graphene when MIXED with some kind of solvent or other 'carrier'? Figure something out for a 3d printer with a wide enough carriage to make planar or eventually-to-be-folded speaker diaphragms. Print on Mylar (1/2 mil? 1/4 mil?) or Kapton. The company I was working with found that getting it into solution was easy. Keeping it suspended (vs. clumping up) was hard. Also, keeping the dry form from forming clumps was a huge challenge...it attracts to itself VERY well. Their "magic" was that their proprietary solution allowed it to disperse and not clump up in solution. 3D printing may or may not work, and unless one needs a 3d structure, there are many other ways to deposit a solution in a pattern that are far easier than 3d printing (I was also looking at state of the art 3D printing...for a related but different reason). Mark |
|
|
|
Post by leonski on Aug 31, 2018 12:54:17 GMT -5
Cerainly many choices in the patterning arena.
We experimented with ElectroStatic a long time ago at work.
And once in liquid form with no clumping? Depending on the 'carrier', I've worked with Photo Lithographic tools (for semiconductor processing) which would 'spin' on a coat to ANY desired thickness. Too Thin COULD leave gaps, but you never went
that thin because of other process reasons. Viscoscity / RPM / Time / Amount determine final thickness and uniformity of film.
Heck for the thickness of film needed for such a good conductor? Forget that I ever SAID 3d. A good, regular printer would work. Once of those used for Architectural or 'Big Print' copy work might be adaptable to making planar drivers?
I don't know the resistivity of such a film which would directly play into needed thickness and currrent carrying capacity. Lot of gaps in what i DO know.
But such fascinating possibilities.
|
|
