Sennheiser HD 598

The HD 598 belongs to Sennheiser's family of open circumaural headphones: the earcups fully enclose the ear and the rear of the transducers communicates freely with the outside. This design choice favours airiness and clarity of reproduction over acoustic isolation, making it a home or office headphone rather than one for travel.

The acoustic design is based on the manufacturer's own E.A.R. (Eargonomic Acoustic Refinement) principle: the transducers are not placed parallel to the ear but angled so as to direct sound towards the ear canal. This angled placement is accompanied by so-called Surround reflectors, whose role is to widen the stereo image and give an impression of distance between the listener and the instruments, rather than a sound stuck to the temples.

On the driver side, Sennheiser employs Duofol diaphragms paired with neodymium magnets and aluminium voice coils. The low moving mass of the assembly serves the reproduction of transients, that is, the fast attacks of a drumstick, a plucked string or a piano, while the energy of the neodymium motor aims for wide dynamics between quiet passages and fortissimos.

Internal resonance treatment completes this design: a lining of compressed cellulose wool is combined with anti-vibration polymer materials inside the shells. The aim is to contain harmonic distortion and prevent the earcup walls from adding their own colouration as the listening level rises.

This profile suits those who listen while seated, in a quiet environment, and wish to follow the sound layers of a recording rather than shut themselves off from the world. The open design lets room noise in and lets the music out: the HD 598 is therefore not suited to public transport or shared offices, but it is well suited to prolonged music listening and film viewing, where the spatialisation claimed for the Surround reflectors finds favourable ground.

When buying a second-hand example, a few points specific to this type of headphone deserve close attention:

• the condition of the circumaural cushions, whose foam sags and hardens over the years, altering both comfort and tonal balance;
• the padding and structure of the headband, stressed with every fitting, as well as any play in the adjustment sliders;
• the grille and protective mesh at the rear of the shells, exposed on an open-back model and easily soiled or dented;
• the detachable cable and its locking mechanism on the earcup side, a loose contact or a silent channel often stemming from there rather than from the transducer;
• the balance between the left and right channels, to be checked at low volume on a mono recording.

A check at moderate volume, listening for any unwanted noise or asymmetrical hiss, generally makes it possible to distinguish minor cosmetic wear from a fault genuinely affecting the transducers.