Bundled witihin the SR-001MK2, SRS-005A or simply on their own, the Stax SR-003 are the most compact, most affordable electrostatic headphone in the world. Their first in-ear model, the electrostatic drivers of the SR-003 do not have the same trouble with lower frequencies as large electrostatic speakers, but they do feature the same unworldly speed and extension. While not as refined as the higher level Stax, which can cost upwards of 400 dollars plus driver unit, the SR-003 features a bassier sound signature often compared to the Stax flagship SR-007MK2. Sadly, due to its electrostatic nature, the SR-003 terminates in a 5-pin pro bias connector, and requires a compatible amp system to work.