This goes onto the list of awesome Graphene things I'll likely have to wait for for some time, along with:
Graphene Supercapacitors [http://www.kcet.org/news/rewire/science/more-good-news-on-th...]
Graphene Antennas [http://bgr.com/2013/03/06/graphene-antenna-research-terabit-...]
and other things I'm most likely missing here. But seriously, the technological possibilities of this stuff baffle me. Hopefully they become the next light emitting diode (in terms of price, availability, flexibility and output compared to previous technology).
I should note that the Sennheiser MX400 headphones in question are a $10 unit. Definitely not the worst you can get for the price, but by no means high-end units. Just something to keep in mind when thinking about this.
Good on the original article to show the "Vdc" bias voltage (battery symbol) required to charge the diaphragm relative to the surrounding electrodes, and to show (conceptually) an inverting unity gain amplifier for one electrode of the signal ("Vin") so that balanced (opposing) electric signals drive opposing sides of the diaphragm.
Without the bias voltage, there would be no electric bias field between either electrode relative to the diaphragm, against which bias fields the signal adds or subtracts in order to move the diaphragm bidirectionally.
The required bias voltage of an electric field headphone element (or speaker) is very much akin to the permanent magnet of a conventional electromagnetic loudspeaker -- both provide a fixed field against which the signal works to produce proportionate mechanical motion.
Whether this bias voltage requirement will eventually result in "phantom power"[1] on analog "headphone outputs" as it has [optionally] for professional analog microphone inputs[1] -- or small power cells and inverting electronics in the headphones or on the headphone wires (perhaps supporting other analog or DSP functions such as active noise cancellation, equalization for flatter response, or decryption of an encrypted digital headphone signal) -- may be up for the market's consideration in a few years.
That response is far from "superb"! If I'm reading the scale right, there's a 30+dB difference between 200Hz and 20kHz. The article explains how a "flat" frequency response is the ideal target, then claims that a graph that is anything but flat is "superb"?
Flat response isn't really the target for headphones. At least not a flat response in the manor these measurements are being taken.
Headphone drivers are very close to your ears which causes frequency dependent effects. Also there are issues with how the sounds bounces around your ears / ear canal / head in general (google Head Related Transfer Function for more).
A 10db drop between about 1khz and 20khz is 'about right' for a flat response during use. Additionally roll off on the low end is also expected in a measurement like this for in-ear headphones, a large amount of gain will be added once these are sealed in your ears.
I am aware of that, but I've listened to cheap earphones, I've listened to the newer low-mid-range Apple earphones, I've listened to $70-range earphones, and I've listened to mid-range ($100-200) studio headphones and mid-range ($700-1500/pr) studio monitors, and there's no way that a response curve largely matching $10 earphones (or even $70 earphones) can be described as "superb".
That said, I'm complaining about the article, not the research. By all means, Berkeley researchers, please continue developing graphene earphones!
Earphones, or rather speakers, are fascinating things. How simple they are in comparison to the many technological leaps necessary to recreate visual input.
(We still don't have decent displays; all of them are flat, and most of them look terrible)
Each microphone is sampling a single point in space over time. It's an incredibly simple signal.
The problem in reproducing it exactly resolves to the problems of materials engineering and efficient coupling of your transducer to the air.
Meanwhile, your brain is doing an amazing job of extracting information from two point signals separated by the width of your skull. There's information that comes from the way that the shape of your ears distorts waves coming from different directions; timing information between the two ears; tilt information from kinesthetics and eyes. All that is handled by systems with a hundred million years or more of evolution in the Earth's biosphere, plus learned updates from your measly few years of life.
And 16 bits per sample, 44.1KHz sampling rate, will suffice to record it all as well as your ears can hear in any sort of normal environment. (A few more bits will suffice if you intend to capture both jet engines and soft breezes in the same recording.)
Microphones have a host of issues as well. But the reason people notice the difference between cheep speakers and good ones is speakers have to deal with an instantaneous signal, if you reincode based on the characteristics of the speaker you can get a lot from even fairly cheap speakers.
I'm not a 100% sure, but it probably involves convolution processing, as is used in some professional speakers - particularly for room optimization[0][1].
i don't have the greatest understanding of how speakers work, so correct me if i'm wrong, but wouldn't an increase in energy efficiency (making the speakers easier to drive) mean that for the same volume level on a source, the graphene speaker be louder?
i sometimes find that at lowest level my headphones can be a bit to loud in some quiet environments, so graphene headphones would be even worse
