I recently discussed my previous experience with Stax electrostatic headphones with joker, who just heard the lineup at CES and we agreed that the SR-009 is nice, very nice! The entire Stax headphone lineup is. But we agreed the SR-003 electrostatic earphones did leave something to be desired. This is in large part due to the limitations of electrostatic drivers, which are dampened by air, and therefore they need to be lighter and thinner the smaller they get. In general, as a material gets thinner and lighter, it becomes more fragile and has trouble withstanding the physical stress a speaker goes through. Stax does a great job with their headphones, and they are working to improve their earphone. Qin Zhou and A. Zettla of the University of California at Berkeley realized the newly discovered super-material graphene could make a great electrostatic driver material.
Graphene is a single atom thick conductive sheet of what is essentially graphite that is 100 over times stronger than an equivalent steel sheet, if you could make one that thin. Thin, conductive, and strong with a high spring constant, graphene could prove to be the material drivers of the future are made of, not gel. Due to the combination of properties, graphene speakers could be several magnitudes more energy efficient than current speaker design, leading to some great new applications. Imagine a portable Stax without the need for a big, expensive amp. The researchers created graphene electrostatic earphones with a 7mm driver that was powered by a 100 V source! They compared their first run earphone with a Sennheiser MX-400, and while the curve doesn’t look great, they did prove their concept works. For more details, read the article published by the Berkeley students, which can be found here: Applied Physics Letters, Vol. 102, Issue 22, June 2013.