Grado Signature S750

The Signature S750 is an open-back wired headphone from Grado, sitting at the top of the brand's Signature series. Its open acoustic architecture allows the rear of the drivers to breathe freely, a design choice that favours an airy soundstage and natural timbre over isolation from the outside world. This is a headphone conceived for relaxed listening, at a desk or in a listening room, connected to a source by cable.

The engine of the headphone is a 50 mm dynamic driver, a generous diameter that gives the diaphragm a substantial emission surface and eases the reproduction of bass registers without apparent strain. The manufacturer states a frequency response of 4 Hz to 48 kHz, a range that extends well beyond the audible spectrum on both ends and reflects a design with no deliberate limitation at the extremes. The nominal impedance of 38 ohms remains moderate, and the sound pressure level of 115 dB at 1 mW indicates high sensitivity: the S750 plays loud with little power and so is content with headphone amplification of reasonable output.

The connection to the source is made via a detachable Signature Gold cable, terminated on the source side by a 6.35 mm jack and connected to the headphone by a 4-pin mini-XLR plug. This detachable connector changes a good deal in practice: the cable becomes a replaceable part rather than a permanent point of failure, and the termination can be adapted to the equipment used. The weight of 480 g places the unit among the substantial headphones, which calls for a proper fit and seated listening rather than use on the move.

This model is aimed at listeners who listen at home, in a quiet environment, and who accept the principle of an open-back headphone: sound escapes, and room noise gets in. It will suit a stationary hi-fi setup as well as an audio workstation, particularly for those seeking an open, articulate reproduction rather than sonic enclosure.

When buying a headphone of this type second-hand, a few points deserve close inspection:

• the condition of the ear cushion foams, consumables that compress, yellow and crumble over the years, and whose wear alters the fit on the ears and therefore the perceived tonal balance;
• the flexibility and integrity of the headband, along with the play in the adjustment arms, which are stressed each time the headphones are put on;
• the cleanliness and mechanical soundness of the 4-pin mini-XLR socket on each earcup: an ovalised or oxidised connector causes channel dropouts;
• the condition of the detachable Signature Gold cable, particularly at the strain reliefs and around the 6.35 mm jack;
• the balance between the two drivers, to be checked at low volume on a mono signal, as well as the absence of crackling or diaphragm rubbing.

The grille and rear of the earcups, inherently exposed on an open-back design, are also worth a look: accumulated dust or deformation of the guard are indicators of the storage conditions the headphone has been kept in.