Ultra-thin diaphragm with MLER 2 electrodes

The STAX SR-009S is an open-back electrostatic headphone built around MLER 2 fixed electrodes and an ultra-thin diaphragm. Gold-plated electrodes help control resonance, while carefully finished openings allow sound to pass through with less air resistance. A precision-machined aluminum enclosure, leather ear pads, and an adjustable headband support comfortable listening.

Multilayer electrodes with a smoother path for sound

MLER 2 advances the multilayer fixed-electrode technology introduced with the SR-009. An updated etching and finishing process smooths the edges of each electrode opening, reducing air resistance and improving acoustic transparency. This gives sound waves a clearer path through the electrode structure.

Gold plating for greater resonance control

The ultra-thin fixed electrodes receive gold plating to help minimize resonance. Gold’s high density adds damping, while its conductivity reduces electrical resistance in the electrodes. These refinements support a presentation with clarity, fine detail, and well-defined texture.

An ultra-thin diaphragm for fast transients

The SR-009S uses a diaphragm made from ultra-thin engineering plastic film. Its low moving mass supports a fast transient response across the audio spectrum, helping reproduce the attack and decay of voices and instruments.

A rigid aluminum enclosure

Precision-machined aluminum provides structural rigidity while keeping weight manageable. The redesigned body further reduces resonance, giving the electrostatic driver a stable supporting structure.

Silver-coated copper cable

The supplied cable uses silver-coated 6N copper with a stated purity of 99.9999%. Its six-strand parallel construction forms a low-capacitance wide cable designed for electrostatic operation. At 8.2 feet (2.5 meters), it provides room to sit comfortably away from your amplifier.

Leather pads for extended listening

Handcrafted ear pads combine genuine lamb leather at the skin-contact surface with high-quality synthetic leather around the surrounding portion. Moderately elastic cushioning provides support, while the leather contact surface helps manage moisture during longer listening sessions.

Ten steps to a comfortable fit

A 10-step headband slider lets you adjust the SR-009S to suit your head shape. The indexed positions make it easy to ensure a consistent fit.

Product highlights

• Push-pull open-back electrostatic design
  
• MLER 2 multilayer fixed electrodes
  
• Smoothed electrode openings for reduced air resistance
  
• Gold-plated electrodes for resonance control
  
• Ultra-thin engineering plastic film diaphragm
  
• Precision-machined aluminum construction
  
• Silver-coated 6N copper cable
  
• Genuine lamb leather ear pad contact surfaces
  
• 10-step adjustable headband
  
• 580V DC bias voltage

Specs

• Model: STAX SR-009S
  
• Type: Push-pull open-back circular electrostatic headphone
  
• Frequency response: 5–42,000Hz
  
• Electrostatic capacitance: 110pF, including cable
  
• Impedance: 145kΩ, including cable, at 10kHz
  
• Sound pressure sensitivity: 101dB at 100V RMS, 1kHz
  
• Maximum sound pressure: 118dB at 400Hz
  
• Bias voltage: 580V DC
  
• Ear pads: Genuine lamb leather at the skin-contact surface, high-quality synthetic leather around the surrounding portion
  
• Headband adjustment: 10-step slider
  
• Cable: Silver-coated 6N (99.9999%) OFC, parallel six-strand, low-capacitance wide construction
  
• Cable length: 8.2 feet (2.5 meters)
  
• Weight without cable: 1 lb (approximately 454g)
  
• Weight with cable: 1.3 lb (approximately 590g)
  
• Channel identification: L and R markings inside the headband assembly, solid line on the left cable, dotted line on the right cable

What’s included

• STAX SR-009S electrostatic headphones with 8.2-foot (2.5-meter) cable