Researchers from the University of California, Berkeley, have developed a new graphene-based earphone-sized speaker - that can actually outperform the best earphones. They say that even with almost no specialized acoustic design, it performs comparably to a high quality commercial headsets (a Sennheiser MX-400 earphone, in fact). The graphene speaker is also highly efficient:

http://www.graphene-info.com/new-graphene-based-speaker-can-outperform-best-commercially-available-earphones