Earthworks (company)
Earthworks is a professional audio equipment company founded by David E. Blackmer in the late 1980s after he left dbx to sell studio microphones, preamplifiers and studio reference monitors.
Their products are based on Blackmer's research into ultrasonic frequencies in sound reproduction and his claims that the time resolution of human hearing is 5 microseconds or better - corresponding to 200 kHz, well above the 20 kHz conventionally accepted as the limit of human hearing.