Наушники — Koss ESP/95X Plus

The ESP/95X Plus is an electrostatic headphone system from Koss Stereophones, sold as a package that pairs the ESP/95X headphone with an E/90 Electrostatic Energizer in updated graphics and colours. The Plus edition wears an exclusive midnight blue finish, adds velour-wrapped ear cushions that are thicker than the pads of the original model and ships with an ESP leather carrying case at no extra charge. Koss describes supply of this edition as extremely limited and covers the system with its Limited Lifetime Warranty.

Key specs that matter

The rated bandwidth runs from 8 to 35,000 Hz, with an impedance of 100k ohms and a sensitivity of 98 dB SPL at 1 mW. The diaphragm is a polyester film 1.5 microns thick. A flat, straight dual-entry cable 1.2 m long, ending in a special pin connector, runs from the earcups to the energizer, and a 1.8 m extension is supplied for users who sit further away. The headphone weighs about 353 g, and its folded dimensions are given as 150 x 100 x 40 mm.

Engineering and use context

Each earcup holds an electrostatic element rather than a moving coil, and the enclosure follows an open-air layout with minimal acoustic dampening, and both the headphone and the energizer housing are built from plastic. Headband, earcups and cable can all be detached. The cups pivot on an adjustable headband and are attached to it by sliding tabs during assembly. On the energizer side, voltage amplification is rated at 60 dB, and the audio output reaches 790 Vrms differential, or 2,200 V peak to peak differential with soft limiting. Channel separation is -80 dB at 1 kHz with 100 Vrms differential output, and the amplifier stage covers 1.5 Hz to 50 kHz. A rectangular 5-pin socket accepts the headphone plug, a green LED shows that power is on, and a front switch turns the unit on and off.

Pairing

A conventional headphone amplifier cannot drive this headphone, which is why the energizer is part of the package. The E/90 takes line signals through rear RCA ports or a 3.5 mm input, and Koss supplies a 0.9 m RCA to RCA lead plus a 0.6 m 3.5 mm to 3.5 mm lead, so a CD player, DAC, preamplifier output or a portable player can feed it directly. The volume control is a split knob giving independent level for each channel, and power comes from an external AC adapter that plugs into a wall outlet.

Alternatives

The Koss ESP/950 is the other electrostatic headphone system in the Koss range.