Sennheiser HD 600

The HD 600 is an open-backed headphone that sits over the ears. Two large elliptical earcups, each faced on the outside with a fine metal grille, hang from flat metal strips that slide out of a padded headband with a firm ratchet. Inside are soft velour pads that clip off for cleaning. A detachable cable runs to plugs at the foot of each cup. It weighs about 260 grams, and a small blue badge on the slider carries the model name. Nearly every part, from pads to cable to headband cushion, can be replaced.

Sennheiser introduced it in 1997 as the top of its open-backed range. Open headphones let sound pass in and out through the back of the cup, giving up isolation for a wider, airier presentation, closer to listening on loudspeakers. Sennheiser built the HD 600 around light aluminium voice coils and neodymium magnets, at an impedance of 300 ohms, high enough that it really wants a dedicated headphone amplifier rather than a portable player. Because sound leaks out of the open backs, it suits quiet rooms and reference monitoring rather than recording booths.

The HD 600 became the standard reference among open headphones. Sound On Sound, reviewing it in 2002, called it the state of the art in moving-coil design and doubted readers would find anything better for reference monitoring. What Hi-Fi? later placed it in its Hall of Fame, alongside the Linn LP12 and the Sony Walkman, and Sennheiser itself still calls it the audio purist's choice and the standard for analytical listening.

For more than twenty years it was sold in a speckled black-and-grey finish. In 2019 that gave way to plain black-grey and a slightly reshaped shell, with no change inside. The consumer side of Sennheiser has since passed to Sonova, and the headphone carries on. Its price is the most telling detail: £249.99 from Sennheiser's shop today, against £249.95 when Sound On Sound reviewed it in 2002.