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World’s first graphene speaker already superior to Sennheiser MX400

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April 15, 2014

This jury-rigged, lab-built graphene speaker is already delivering better sound quality th...

This jury-rigged, lab-built graphene speaker is already delivering better sound quality than the commercially-available Sennheiser MX400

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Graphene is frankly just showing off at this point. Not content with breezing in and smashing records in solar efficiency, kicking the butt of lithium-ion batteries, being the strongest known material in the Universe, being 1,000 times more light-sensitive than any known camera sensor and a thousand other achievements, now this smug supermaterial is having a crack at audio. How’s it going? Well, with basically zero acoustic development, a graphene loudspeaker is already boasting a better frequency response curve than a set of Sennheiser MX-400s.

Speakers are basically membranes that are moved back and forth to produce pressure waves in the air that we perceive as sound. To do that, you need a membrane to vibrate, some sort of driver to vibrate it, and some sort of spring effect to bring the membrane back to its starting position at rest.

The heavier the membrane, the more momentum it has on the move, and the more energy needs to go into moving it or changing its direction. Graphene, as we are all constantly reminded, is ridiculously light, stronger than anything else, and can be made extremely thin. Oh, and it conducts electricity, of course. So a team of scientists at UC Berkeley rigged up a graphene diaphragm between two silicon electrodes and ran some acoustic tests to see how it performed as a 7 mm diameter earbud-sized speaker.

How did it go? Well, it’s graphene, so you can probably guess. Compared against a Sennheiser MX-400 earbud off the shelf, here’s the frequency response charts (noting that a flat line is the ideal shape):

Frequency response charts for the graphene earbud (top), the Sennheiser MX400 (middle) and...

The jury-rigged graphene earbud is very close to the Sennheiser through the low and midrange frequencies, and significantly flatter in the high frequency range above 5 kHz. That’s without any acoustic development at all – and still the researchers reported "the fidelity is qualitatively excellent when listening to music."

What’s more, it uses very little energy due to the extremely light membrane, and researchers noted, "The configuration described in this letter could also serve as a microphone. The microphone should also have excellent response characteristics due to the graphene’s ultra-low mass and the excellent coupling to ambient air."

Now, the Sennheiser MX-400's are a ten-dollar set of earbuds, not some audiophile headset. But it’s a ten dollar earbud that’s taken a long time to develop, versus what may be the very first graphene speaker ever assembled.

Will it ever hit the market? Well, that’s a different matter. But if and when mass production for this stuff becomes cheap and easy, pretty much every sector in engineering and technology will be set to take a giant leap forward.

Source: Arxiv (PDF)

About the Author
Loz Blain Loz has been one of Gizmag's most versatile contributors since 2007. Joining the team as a motorcycle specialist, he has since covered everything from medical and military technology to aeronautics, music gear and historical artefacts. Since 2010 he's branched out into photography, video and audio production, and he remains the only Gizmag contributor willing to put his name to a sex toy review. A singer by night, he's often on the road with his a cappella band Suade.   All articles by Loz Blain
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8 Comments

The Senheiser 'phones appear to be 'dynamic' i.e. they are of moving coil construction which means that the mass of the coil assembly (which is attached to the diaphragm) is also having to be moved.

The Graphene unit is electrostatic and has no drive coil i.e. it is moved by electric fields. Consequently the assembly can't fail to be lighter and so is bound to move more freely and have better transient and frequency response.

The article does nor compare like for like. Electrostatic headphones are available (e.g. Sennheiser Orpheus HE 90) so the article should compare the Graphene unit with these if objectivity were at all important!

Sheldon Cooper
16th April, 2014 @ 02:52 am PDT

This sounds very cool (zero sarcasm included), but I'm really interested in seeing what this can do for the quality of laptop speakers, and then up to decent-sized home stereo speakers. Perhaps we can finally see some decent quality "flat" speakers again?

Purple-Stater
16th April, 2014 @ 03:53 am PDT

The overriding problem with sound reproduction from laptops is that the loudspeakers are necessarily small and so are little more than tweeters (or mid-range units are best) so invariably sound 'tinny' - you need large area cones / diaphragms backed by a large cabinet volume to produce and propagate low frequencies into free air; having similarly tiny electrostatic speakers will do nothing to improve this.

You can hear bass in earphones (driven by tiny diaphragms) simply because they are virtually directly coupled to the eardrums with no free air dissipation.

Domestic electrostatic speakers have been available for many years - Quad produced their first model in 1957.

Sheldon Cooper
16th April, 2014 @ 05:07 am PDT

The high peak in the MX400's probably make them 'sound clearer' compared to the graphene headphones. The practical hearing range of most adults is around 14khz. While impressive, the graphene headphones would be called 'muddy' by reviewers.

dink
16th April, 2014 @ 09:09 am PDT

Typical audio snake oil. A diaphragm of simple Saran Wrap is already light enough that the load seen by the driver is almost purely that of the air it drives (in parallel with a big capacitor.)

Second, being a conductor confers a disadvantage, not an advantage. For an ESD the the diaphragm surface needs to be a high resistance. Low enough that charge can migrate to it and cover it at startup but high enough that it can't move on that surface within a cycle of the lowest frequency of interest. If it can move freely it will move as the diaphragm flexes to the point closest to the electrodes. This introduces non-linearity and distortion. Lots of it.

Third there is absolutely no basis for saying that the curve shown for their device is superior to that of the Senn. I'm rather experienced at this and what is shown deviates a lot from the loose consensus of what is best. The Senn is much closer. Where it is measured and how it is measured is more important than the characteristics of the device itself and there is as yet no standardized measurement setup and resulting spectrum that can in any way be agreed on to be "optimal."

Last, the amount of wiggle room within the error bars of their graph is way more than enough to cover a wide range of responses most of which would sound horrible.

DonGateley
16th April, 2014 @ 12:20 pm PDT

Hi, you will have to edit the article. A flat line is NOT the target response for headphones. Headphone response is measured at the inner ear and the ideal/target response looks like this (black line): http://www.innerfidelity.com/images/140202_Blog_HarmanResearchUpdate_GraphDFvsOliveWelti.jpg

The MX400 is actually closer to the correct target.

OTOH I don't know enough about how the measurements were made to get specific.

One thing for sure: I too am excited about the potential for graphene speaker drivers to avoid breakup modes and enable some pretty special loudspeakers (or headphones). Can't wait!

T N Args
16th April, 2014 @ 06:36 pm PDT

"Better than the Sennheiser" is REALLY a stretch. the Sennheiser is much flatter through the critical 1-5KHz ranges and only starts to fall off faster then the other after around 10KHz, where there is not a lot going on.

Yes I understand that the graphene unit has no acoustic development, but to state that the graphene curve is better than that Sennheiser curve is simply not correct - especially from a listening point of view.

"Nearly as good as the Sennheiser MX-400" would be a much more accurate statement.

jjsmail
16th April, 2014 @ 06:37 pm PDT

To allow easy comparison of two complex charts like those presented they should have been superimposed. Having said that, the graphene bud would be much easier to equalise to achieve a "flat" and extended frequency response.

Tony Morris
16th April, 2014 @ 07:07 pm PDT
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