Headphones — Stax SR-007S

The SR-007S is an open-back electrostatic model from Stax, the latest version of a headphone line that began in 1998. In the current range it sits well below the SR-X9000, yet it borrows several refinements that Stax first developed for that top model.

Key specs that matter

Frequency response runs from 6Hz to 41kHz. Electrostatic capacitance is 110pF including the cable, and impedance is 145k ohms at 10kHz. The SR-007S runs on a 580V DC Pro bias voltage, and sensitivity is 101dB at an input of 100Vrms. It weighs 430g.

Engineering and use context

Stax uses a push-pull electrostatic element in this model, fitted with newly redesigned large circular fixed electrodes. Their air vent holes are 20% smaller in diameter than on earlier models, which Stax says improves airflow and gives a smoother, more even frequency response. A stainless steel Anti-Resonance Structure stiffens the assembly to cut resonance in the earcups. The sheepskin earpads rotate for a better fit and more comfort, and a redesigned inner earpad changes how the cup absorbs sound. Unlike earlier SR-007 generations, which had a fixed lead, this version uses a detachable low-capacitance cable, so it is easy to service and can be upgraded later.

Pairing

An electrostatic headphone works on a different principle from dynamic and planar magnetic designs, and an ordinary headphone amplifier cannot drive it at all. The SR-007S needs a dedicated Stax energizer or a hybrid driver unit that supplies the Pro bias voltage and the wide voltage swings the diaphragm requires.

Alternatives

The Stax SR-X9000 is the open-back electrostatic model above the SR-007S, and it is the source of the refinements passed down to it.