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Massdrop x Koss ESP/95X Electrostatic System

Massdrop x Koss ESP/95X Electrostatic System

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Product Description
A revival of the standard-setting ESP/950 released by Koss in 1990, these headphones bring electrostatic quality into a whole new price bracket. Initially designed for live recording, the ESP/950 came with a large carrying case and a battery pack to power the required energizer: a special amplifier for electrostatic drivers Read More


ESP/95X Electrostatic Headphones

  • Acoustic principal: Circumaural open-air design with minimal acoustic damping
  • Diaphragm: Ultra-low-mass 1.5-micron C-grade polyester film coated with semiconductive material
  • Diaphragm radiating surface area: 7 sq in (45.6 sq cm)
  • Frequency response: 8 Hz–35 kHz
  • Headband: Stainless steel, extendable
  • Headband cover: Wide leatherette-style vinyl with 12mm-thick polyethylene foam padding
  • Yokes: Horizontal and vertical pivoting with integral headband lock-and-detach mechanism
  • Cushions: Velour-wrapped foam
  • Cup size, including cushions (H x W x D): 5.9 x 3.9 x 1.6 in (15 x 10 x 4 cm)
  • Cable: Straight, dual entry, 4 ft (1.2 m) with 6 ft (1.8 m) extension 
  • Weight: 12.45 oz (353 g)

E/90X Electrostatic Energizer

  • Frequency response: 1.6 Hz–50 kHz (-3 dB), 100 Vrms differential output
  • THD + N: 0.001% at 1 kHz, 100 Vrms differential output
  • Input impedance: 100 kohms
  • Input level: 1 Vpk (for full power output)
  • Voltage amplification: 60 dB
  • Audio output voltage: 790 Vrms differential; 2,200 Vpk-pk differential with soft limiting
  • Channel separation: -80 dB at 1 kHz, 100 Vrms differential output
  • Signal-to-noise ratio: -100 dB at 100 Vrms output
  • Bias voltage supply: 600 VDC
  • Signal polarity: Absolute phase (non-inverting)
  • Volume control: Dual concentric continuous audio taper high-quality potentiometer with split shaft for balance
  • Switch: Power on/off rocker
  • Input jacks: RCA type (left and right), 3.5mm stereo, AC/DC adapter
  • Power: AC adapter power supply for E/90X (included, select 120V or 220V)
  • Power consumption: 320 mA DC current at normal listening levels
  • Dimensions (H x W x D): 2.6 x 4.3 x 6.1 in (6.5 x 11 x 15.5 cm)
  • Weight: 17 oz (482 g)


  • ESP/95X electrostatic headphones
  • E/90X electrostatic energizer
  • 120V or 220V AC adapter (add plug adapter for your country’s outlet)
  • 3 ft (0.9 m) RCA-to-RCA cable
  • 2 ft (0.6 m) 3.5mm–to-3.5mm cable
  • 6 ft (1.8 m) extension cable 
  • Koss's limited lifetime warranty (see warranty card)


We get it. Sometimes what you ordered just doesn’t work out. If that’s the case for you, don’t fret! All customers (both US and international) may return this item in new, unused condition within 30 days of delivery.


Estimated ship date is Mar 18, 2021 PT.

Payment will be collected at checkout. Cancellations are accepted up to 2 hours after checkout for in-stock items, or up until pre-order ships.

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