STAX SR-009 Earspeakers


Trade-in available

The SR-009 is the product of STAX Audio’s repeated research into technology and materials without deviating from their goal – everything should contribute to quality music reproduction.

All aspects of this earspeaker, including the diaphragm, electrodes, enclosure, headband and cable, have been redesigned with this in mind. The result is one of the most effective and popular electrostatic headphones available.

SKU: USV-STAX-SR009 Category: Tag:



SR-009 is the product of STAX Audio’s repeated research into technology and materials. If a technology is not suitable for music, one should not adopt it. Even if it is high-tech.

A newly developed sound element has been adopted for the SR-009. New high polymer ultra-thin film material (called super engineering plastics) is employed for the diaphragm, delivering superior tone quality, excellent frequency characteristic, and a vast dynamic range.

New electrodes named MLER (Multi Layer ElectRodes) have been developed to realize the plane drive of the whole film diaphragm surface. While infinite thinness and flatness are required for the fixed electrodes, they simultaneously need to have other characteristics, for instance low resonance and high transmissivity of the sound wave.

Aluminium is a good material for sound and audio equipment in general, and SR-009 makes abundant use of it. Almost every part of SR-009 enclosure is manufactured through precise machine processing.

High-quality copper wire of 99.9999% purity adopted for the cable, silver-coated and finished with the most suitable structure to drive the earspeaker.

The new design earpads are indivually made by craftsmen, and feature both real leather to cope with humidity, plus synthetic cushion material with moderate elasticity. The new earpad enables hours of comfortable listening to music.

The headband (arc) is equipped with a 10-step position adjustment slider mechanism, and corresponds to an extremely wide range of cranial shapes.

Electrostatic technology

Electrostatic transducers consist of two parallel-arranged fixed electrodes with a very thin high-polymer film diaphragm sandwiched and suspended in the middle of the electrodes.

The diaphragm is supplied with the biasing voltage from the energizing adaptors or from the driver unit.

When the fluctuating voltage of the audio signal is applied to the electrodes, the diaphragm is pulled by one electrode (which has the opposite charge of the diaphragm) and simultaneously pushed by the other electrode (which has the like charge of the diaphragm).

This continuous flow of alternating voltage causes the diaphragm to vibrate in faithful compliance with the amplifier output without lag, assuring undistorted sound waves. This is why the STAX electrostatic earspeakers sound so good.

Electrostatic driver required

Electrostatic reproduction has many quality advantages, however such units cannot be used directly with a conventional headphone jack, and require a special electrostatic amplifier (driver) unit.

The vibrating diaphragm requires Bias voltage of 580V (almost no current). Relatively high signal voltage to the fixed pole (up to 300-600V) must be supplied as push-pull, a rather special electrical signal. The STAX series of driver units are dedicated amplifiers strictly for STAX headphones.


  • New high-polymer diaghragm
  • Multi-layer electrode design
  • Precision machined enclosure
  • High-purity copper cable
  • Real leather earpads
  • 10-step adjustable headband mechanism


  • Type: Push-Pull Open Back Circular Electrostatic Headphone
  • Frequency Response: 5Hz – 42kHz
  • Electrostatic Capacitance: 110pF (including cable)
  • Impedance: 145k ω (including cable, at 10kHz)
  • Sound Pressure Sensitivity: 101dB / 100V RMS 1 kHz
  • Maximum Sound Pressure: 118dB / 400Hz
  • Bias Voltage: 580V DC
  • Channel Identification: L / R indicated on the arc assembly (inside head spring). Left channel cable is marked with a solid Line. Right channel is marked with a dotted Line.
  • Ear Pads: Genuine Lamb Leather (direct skin contact), high-quality synthetic leather (surrounding portion)
  • Cable: Silver-coated 6N (99.9999%) OFC parallel 6-strand, low-capacity special wide cable, 2.5m full length
  • Weight: 1lb (0.45kg) without cable / 1.3lb (0.59kg) with cable

More Information



Founded in 1938, STAX brought the world's first electrostatic headphone to market in 1960 and today continues their long tradition by offering the finest products for both professional and audiophile applications.

All STAX headphones are referred to as "earspeakers" - the company states that such ultra-high fidelity devices can only be compared with the best cost-no-object loudspeakers, not other headphones. Their unique amplifiers, earspeakers and drivers are highly sought-after products, and extremely well considered by aficionados in the audio industry.

Unilet Sound & Vision are one of the oldest STAX dealers in the UK, and one of the very few official outlets for their products.

STAX | Unilet Sound & Vision

Additional information

Weight 0.59 kg


Purchase Options

Click & Collect, Trade-In Available


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