Monday, August 2nd 2021

Ultra-tiny Carbon Nanotubes Deliver Big on Headphone Audio Experience

I know what you are thinking—this isn't the typical news content we see on TechPowerUp. Yes, we do cover audio products with plenty of reviews here, including Audeze planar magnetic headphones. When Audeze mentioned there's a whole different thing coming up, and that it involves carbon nanotubes (CNTs), I was quite intrigued. Some of you may have picked it up by now, but all the neat toys I have access to and used in several reviews come because I am a research scientist by profession, with a specialization in carbon nanomaterials including CNTs. So this news post is about my attempt to help explain why the Audeze technology is such a big deal. This is not a review of the actual devices and neither is it a sponsored post, or even solicited by Audeze. It is purely me geeking out about a fairly novel use of CNTs in the audio world, especially when there have been CNT coatings on a few dynamic drivers before but barely put to the potential capable until now.

See, the whole reason the Audeze CRBN (Carbon, get it?) even came about is because an indirect research colleague of mine, Prof. Mark Cohen from the University of California, Los Angeles as well as his startup company SMRT Image, saw a need for a more calming influence for patients undergoing fMRI imaging, as well as better means for the technicians to communicate with said patients while they are inside an operating MRI machine. If you have ever been inside one, you would know that thing gets real loud with magnetic coils rapidly going around and clacking noises galore. Audeze is also based in California, and multiple years of research led to the development of the Audeze CRBN—starting off for medical applications and then coming out also as a high-end retail headphones experience based on the knowledge and IP gained in the process. Read past the break for more on the science and tech, if this is of interest to you!
At this point, a logical question would be what happens if the sounds are loud inside an MRI machine? Can't the patient simply wear ear protection such as ear defenders that have been successfully used in other loud use cases, including construction? Typical noises inside an MRI machine can get as loud as 120 dB, which is similar to having a jackhammer going next to you. More often than not, there is also a head constraint device used to mitigate motion which in turn does not allow for larger ear defenders to be used. Any magnetic/ferromagnetic metal is also a big no-no since the magnetic coils of the MRI can rip them out owing to the strong magnetic field. This is why piercings are to be removed prior to imaging, else you might end up replicating one of the few good scenes from Terminator Genisys. Small ear plugs only go so far too in terms of isolation provided, especially in the absence of a custom fit. In fact, even some metals can generate Eddy currents that can impact imaging inside. When the slightest of motion can result in poor imaging, it is important to have good noise isolation. At the same time, having a clear line of communication with the technician is also critical, which makes this harder to achieve.

Current solutions tend to go the way of silicone earphones without a lot of metal in them, which means the actual drivers have to be configured in a challenging manner. Having aided with some MRI research myself, albeit for different purposes, I was thus curious about what the answer was long-term for patients who get stress and anxiety over a scan to begin with, let alone any effects of claustrophobia and phonobia. Active noise cancellation seems like the way to go, but once again the actual drivers for the headphones are a challenge since you can't use wireless tech here and specialized MRI noise cancellation is either $$$$$$ in the form of external drivers with long, shielded cables or not very effective. There is thus a need for conductive driver materials which are not metallic, or at least non-magnetic and unaffected by the magnetic flux generated by the MRI. Planar magnetic headphones are clearly not the answer either, since they are driver by high magnetic flux internally so any external magnetic field can cause all sorts of havoc.
Enter carbon nanotubes, and more specifically single-walled carbon nanotubes at that. A single wall carbon nanotube (SWCNT) is a carbon allotrope envisioned by rolling up a graphene sheet, which in turn is a single layer of graphite that itself can be visualized as a flat sheet of carbon atoms. The nature of rolling said sheet dictates what is called the chirality of the SWCNT, with the maximum possible chiralities and chiral angle (of rolling) between 0° and 30° relative to the plane, based on thermodynamics allowing only those to exist in a stable state. One of these extremities (armchair) is the best possible electrical conductor, and the other extremity (zigzag) a semiconductor. Anywhere in between and you get semi-metals and metals in that you have electron transfer but it is still carbon on the macroscale. See where I am getting at? If the diaphragm of a typical headphone driver setup were to be made of SWCNTs, then that would solve the big issue from above. The next challenges involve (a) how to get the SWCNTs as a diaphragm/transducer, and (b) how to actually drive it. Audeze and its collaborator ended up going with a suspension of SWCNTs in a polyimide, which is one of the several options available. I might have gone another route depending on the suspension thickness and desired qualities, but here we are anyway. This suspension allows a stable film to be made that has the SWCNTs inside, ideally uniformly to thus also have uniform electrical conductivity.
The second challenge was seemingly addressed by using these ultra-thin SWCNT diaphragms as a conductive media for electrostatic charge, which forms the basis for electrostatic headphones. I don't have a lot of experience with this class of headphones yet, but I understand the science behind how they work in needing a high driving potential (think 800-1000 Vrms) to generate the electrostatic field that in turn vibrates the diaphragm to generate sound waves. This decoupling mechanism of driving the headphones without the need for classically metallic drivers should help also place active noise cancelling materials along the way, which seems to have been done with the MRI imaging version of the Audeze CRBN that I understand will be sold through SMRT Image directly in Q4 2021.

The other end of this technology comes with the retail version, just referred to as Audeze CRBN with a rated 100 pF electrostatic capacitance. As it turns out, having the ultra-thin diaphragm allows for more accuracy in the reproduced sound signature, or so Audeze claims anyway at this point without much independent testing having been done aside from a few music recording artists sharing their opinions. It does have some logic behind it, since the way I see increased audio fidelity and resolution to be is to have effectively an ultra-thin diaphragm with nothing in front of it, and as uniform a force as possible pushing and pulling it back as needed. Planar magnetic drivers come close, but ribbon drivers as seen in the recently launched and sold-out Audeze LCD-R are a further step in that direction. With these electrostatic drivers, Audeze and everyone else in the game aims to go even beyond in the race for extreme neutrality and accuracy, but with the added benefit of not weighing as much as the typical full-size planar magnetic drivers either. Take that for what you will, but music monitoring is going to be a key use case here if so. If you have $4500 to spend on a pair of the Audeze CRBN, and more for a standard electrostatic amplifier using the 5-pin connector and rated for 570 V, then you can try this out for yourself when orders open up on the Audeze website as well as some retailers. Once again I have to stress that I do not have any idea how these sound at this point or whether they merit the money. Hopefully some of you found this interesting, and feel free to share your thoughts as comments below.
Source: Audeze
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47 Comments on Ultra-tiny Carbon Nanotubes Deliver Big on Headphone Audio Experience

#1
TumbleGeorge
Too many complexity just for audio. I read before some time ago how cows which hear (classical)music produced more milk...
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#2
Chomiq
Should have opened with $4500.
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#3
VSG
Editor, Reviews & News
ChomiqShould have opened with $4500.
Not a product review, this is more a primer on the CNT tech itself.
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#4
Chomiq
VSGNot a product review, this is more a primer on the CNT tech itself.
In that case I do wonder how they solved the problems with dispersion inside the polymer matrix. You align those nanotubes incorrectly and you might have completely different results.
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#5
VSG
Editor, Reviews & News
ChomiqIn that case I do wonder how they solved the problems with dispersion inside the polymer matrix. You align those nanotubes incorrectly and you might have completely different results.
Now you know why I was saying I might have gone another route for the dispersion :)

I don't have all the info on this since of course they won't share it all, but I plan to ask them more shortly out of curiosity.
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#6
Chrispy_
Interesting article regarding the concept of active noise-cancelling in an MRI room, but this is so far beyond the point of diminishing returns for consumer audio that even most of the people spending $1000 on earbuds are going to balk at this!
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#7
P4-630
TumbleGeorgeToo many complexity just for audio. I read before some time ago how cows which hear (classical)music produced more milk...
Or how hardrock music makes plants grow better :pimp:

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#8
yotano211
TumbleGeorgeToo many complexity just for audio. I read before some time ago how cows which hear (classical)music produced more milk...
My old girlfriend had that problem.
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#9
bug
ChomiqShould have opened with $4500.
Why? Were you expecting cutting-edge audio tech for ~$100?
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#10
Tigger
I'm the only one
There's always some nugget who will pay $4500 for headphones so why not. My mate once payed £80/metre for speaker cable
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#11
bug
Gruffalo.SoldierThere's always some nugget who will pay $4500 for headphones so why not. My mate once payed £80/metre for speaker cable
Well, this is new tech, so there's a considerable initial research waiting for RoI right there.
And there are those that genuinely need the high-end equipment.

That said, I still remember the story when a fan was telling a band member how many tens of thousands of $ he invested in audio equipment to listen to their works. After he finished, the band member was like "yeah, well, the equipment in the studio we record our works, costs less than that". But the end of the day, people don't tell how to spend my money, I don't tell them how to spend theirs.
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#12
TumbleGeorge
bugWhy? Were you expecting cutting-edge audio tech for ~$100?
Where is problem to sold "cut-ting egg audio for $100. You just won't bet 3000% net profit.
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#13
Tigger
I'm the only one
bugWell, this is new tech, so there's a considerable initial research waiting for RoI right there.
And there are those that genuinely need the high-end equipment.

That said, I still remember the story when a fan was telling a band member how many tens of thousands of $ he invested in audio equipment to listen to their works. After he finished, the band member was like "yeah, well, the equipment in the studio we record our works, costs less than that". But the end of the day, people don't tell how to spend my money, I don't tell them how to spend theirs.
Wow you're touchy, didn't realise it mattered so much to you
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#14
Mistral
Is the guy on the second photo in a coma from hearing the price?
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#15
bug
TumbleGeorgeWhere is problem to sold "cut-ting egg audio for $100. You just won't bet 3000% net profit.
More expensive equipment has nothing to do with 3,000% margins. Not even if you're buying Bose.
Gruffalo.SoldierWow you're touchy, didn't realise it mattered so much to you
Not sure what made me sound touchy, I just pointed out new tech is expected to be expensive. And then I said I don't care how much people spend on their audio equipment (fwiw, my most expensive cans were ~$200).
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#16
lexluthermiester
ChomiqShould have opened with $4500.
Right? Seriously, who would spend that on a set of headphones?
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#17
VSG
Editor, Reviews & News
lexluthermiesterRight? Seriously, who would spend that on a set of headphones?
Lots, as it turns out. Audeze released a limited edition of another headphones ($2500) last month which sold out within minutes: www.audeze.com/products/lcd-r
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#18
lexluthermiester
VSGLots, as it turns out. Audeze released a limited edition of another headphones ($2500) last month which sold out within minutes: www.audeze.com/products/lcd-r
While there's a fair number of those who are rich and can easily afford it, there's got to be a fair number of people who are just foolish with money..
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#19
VSG
Editor, Reviews & News
lexluthermiesterWhile there's a fair number of those who are rich and can easily afford it, there's got to be a fair number of people who are just foolish with money..
Simultaneously, people would think TPU readers are crazy for spending so much money on PC hardware too. If we all acknowledge that there are different interests and spending freedom, then everyone will live happily :D
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#20
TumbleGeorge
bugMore expensive equipment has nothing to do with 3,000% margins. Not even if you're buying Bose
Yes there is 3-4 nano... vacuum tube lamps for $0.25 per unit second hand(set offer prices from low to high).
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#21
Franzen4Real
I know what you are thinking—this isn't the typical news content we see on TechPowerUp.
So this news post is about my attempt to help explain why the Audeze technology is such a big deal. This is not a review of the actual devices and neither is it a sponsored post, or even solicited by Audeze. It is purely me geeking out about a fairly novel use of CNTs in the audio world, especially when there have been CNT coatings on a few dynamic drivers before but barely put to the potential capable until now.
In my opinion-- TPU could use more content like this. Sure it may not be typical, but it is tech and it is sort of "outside the box". There are plenty of press releases, leaks, and rumors posted daily. Thoughtful original content like this are a great supplement TPU's already fantastic reviews.

I found it quite interesting, thank you for taking the time to write it up.
VSGSimultaneously, people would think TPU readers are crazy for spending so much money on PC hardware too. If we all acknowledge that there are different interests and spending freedom, and everyone will live happily :D
:toast:
Posted on Reply
#22
lexluthermiester
VSGSimultaneously, people would think TPU readers are crazy for spending so much money on PC hardware too. If we all acknowledge that there are different interests and spending freedom, and everyone will live happily :D
That depends on context. It's one thing to spend $4500 on a highend PC that actually does a whole bunch of somethings very well and very fast, so such pricing is not unreasonable and never has been. $4500 for a set of headphones could be considered excessive(perhaps even opulent) by MOST peoples standards..
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#23
Ferrum Master
Electrostats? Not again... is it 1950ties again?

If read this, and thought it really is something new... it has still has the all same cons and pros as any ribbon speaker.

I would like to remind all, that the production and mixing is set a norm with reference speakers, well usually, as these days even sound engineers are deaf. Using this will not contribute to better musical experience, but vice versa reveal any mixing ugliness in the spectrum past 1KHz, that with these will be inheritably attenuated. It will not be what it was meant by the artist or the sound engineer for you to be delivered, unless your a masochist. It will not be ones cup of tea for 99% of population, even less for those willing to spend the money.

Electrostats are not the holy grail. The ugly side. They attract dust, particles, moisture, thus they deteriorate fast, get holes in it... carbon or not, high voltage and a particle will damage it... they are fragile and not robust. Pairing with random amplifier will definitely damage them, they are highly capricious.

A tube amp in modern days? It is only for enthusiasts and learning. It is a dead horse. You cannot obtain the parts that were made during early cold war. The leftovers or Russian counterparts do not have the plate(anode) material purity isn't there, military ain't using them anymore, thus no money pours in like there is no tomorrow to make a better performing tube and get a contract. If you were lucky and compared, you simply will calm down and not pursue it anymore. It is a thing of past. With exception for guitar amps, where distortion is the main goal and the more distortion the merrier.
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#24
Tigger
I'm the only one
Hands up TPU members if you could, note could buy these........tumbleweed. thought so. These are for the maybe 1% that could afford them, let alone actually would pay this much. So i agree with Lex. The cost of these is beyond a high end PC. These are for UBER HiFi nuts, not the average rich person who probably still does not spend this much on headphones
VSGLots, as it turns out. Audeze released a limited edition of another headphones ($2500) last month which sold out within minutes: www.audeze.com/products/lcd-r
Sold out in minutes, shame none of them left a review, sheesh high end buyers
Posted on Reply
#25
Ferrum Master
Gruffalo.SoldierSold out in minutes, shame none of them left a review, sheesh high end buyers
Prolly went to some UAE resident.

During the days actually 5 star Hotels were buyers of uber premium gear for their most expensive rooms. Considering how costly were those rooms, it paid off really fast. They had a lot of obscure high end gear. I had my hands on it in the past, as they tend to get old and not so shiny anymore, thus they often got sold for pennies.

So basically there is a niche for anything if you spin it correctly PR wise. If this has place on TPU? Definitely not.
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