Headphones — Sennheiser HD 600

Sennheiser, the German audio company, introduced the open-back, over-ear HD 600 in 1997. It has stayed in production for decades and is used by sound engineers as a reference. Production takes place in Ireland and includes the selection of matched driver pairs. The current production version, available since 2019, keeps the original specification while updating details.

Key specs that matter

The HD 600 uses 42 mm dynamic drivers. Frequency response is 12 Hz to 40.5 kHz, nominal impedance is 300 ohms and sensitivity is 97 dB SPL at 1 V. Total harmonic distortion is 0.1%, the load rating is 200 mW and contact pressure is about 2.5 N. Without the cable the headphone weighs 260 g. The detachable double-sided cable is 3 m of oxygen-free copper, with 3.5 mm and 6.3 mm jack connection.

Engineering and use context

The drivers are hand-built, with aluminium voice coils kept light to reduce moving mass. Neodymium ferromagnetic systems, optimised by computer to minimise harmonic and intermodulation distortion, provide the sensitivity and dynamic range. Each earcup is open, with a metal mesh cover that lets the rear of the driver radiate freely. This avoids the resonances of a sealed chamber, but the headphone leaks sound and gives no isolation from the room. The response is diffuse-field equalised, a target meant to reproduce the response of a reference listening environment.

The high impedance means very low driver current at a given level, but it needs a source capable of a larger voltage swing. The cable plugs into each earcup through separate two-pin connectors, the same type used by the HD 650 and HD 660 S, so it can be replaced or upgraded. Circumaural velour earpads and a cushioned headband spread the clamping force over long sessions. Earpads, the headband pad and the cable are all sold as spare parts, so a worn pair can be restored rather than replaced, and Sennheiser supplies the headphone with a two-year warranty.

Pairing

Phones and laptops often cannot drive the HD 600 to full level. Dedicated headphone amplifiers with several volts of output, including valve output-transformerless designs, are the natural partners, and a balanced cable allows connection to balanced amplifiers.

Alternatives

The Sennheiser HD 650 is the related open-back model of the same family with a different tuning.