STAX SR-X9000

The SR-X9000 is the result of over eight decades of STAX expertise in designing electrostatic transducers. It uses four-layer MLER-3 technology and a diaphragm 20% larger than that of the SR-009S. Handmade in Japan, it features a detachable cable system and a machined aluminum chassis.

A technological feat born from two decades of research

The genesis of the SR-X9000 can be traced back to the mythical SR-Omega of the 1990s, of which only 600 units were produced due to the manufacturing complexity of the metal mesh electrodes. This technical limitation, which made the electrodes prone to parasitic resonances, was ultimately overcome thanks to twenty years of refining manufacturing processes and the thermocompression bonding technique developed during the creation of the SR-009 and SR-009S.

At the heart of the SR-X9000 lies MLER-3 (Multi-Layer-Elect-Rords) technology, a four-layer structure combining circular metal mesh electrodes and conventional etched electrodes. This complex configuration requires meticulous manual assembly, with each unit built individually by skilled craftsmen. The gold-plated electrodes are bonded by thermal diffusion, creating a rigid structure that eliminates unwanted vibrations while optimizing acoustic transmission.

The diaphragm, made from an ultra-thin engineering polymer film, has a surface area increased by 20% compared to the previous model. This dimensional expansion, combined with near-zero mass, enables blazing transient response and a frequency range extending from 5 Hz to 42 kHz. The machined aluminum chassis surrounding each transducer firmly secures the assembly and annihilates any undesirable structural vibration.

Design and ergonomics: the alliance of metal and leather

The SR-X9000’s stainless steel headband marks a significant evolution from previous generations. This metal structure better resists torsion and ensures increased stability when worn. An I-shaped aluminum stabilizer crowns the headband, reducing vibrations that could be transmitted to the transducers. The nine-position adjustment system with a click mechanism allows for precise fitting tailored to every morphology.

The genuine lambskin earpads offer remarkable breathability and softness for long listening sessions. The part in direct contact with the skin uses exclusively genuine leather, while the perimeter employs high-quality synthetic leather. The headband, also in genuine leather, ensures optimal comfort with no pressure points. At 432 grams (without cable), the SR-X9000 remains surprisingly light given its robust metal construction.

A particularly welcome innovation concerns the protective grille. Unlike earlier models where this grille was parallel to the transducer, creating harmful direct reflections, the SR-X9000 adopts an inclined design. Pillars of different heights at the front and rear alter the gap between the sound element and the grille, thereby controlling the reflection angle and enabling a smoother sound flow.

Detachable hybrid cabling: flexibility and performance

For the first time in a flagship STAX headphone, the SR-X9000 offers a detachable cable system. Two cables are included (1.5 m and 2.5 m), allowing the setup to be adapted to the amplifier’s location. This modularity also facilitates maintenance and paves the way for future cable upgrades.

The cables employ a sophisticated hybrid structure: the core uses three annealed 6N OFC copper strands (99.9999% purity) with a diameter of 0.14 mm, surrounded by nine annealed silver-plated copper strands of 0.08 mm. This six-conductor parallel configuration, in a special wide low-capacitance format, optimizes bass transmission via ultra-pure copper while favoring high frequencies thanks to the silver plating.

The cable input connectors are angled forward according to ergonomic principles, reducing the strain from cable weight during listening. Left/right identification is by a continuous gold line (left channel) and a dotted gold line (right channel) on the cable. The standard five-pin termination ensures compatibility with all STAX electrostatic amplifiers using the 580-volt Pro bias.

Sound reproduction: the balance between musicality and precision

The SR-X9000 develops a distinct sound signature that doesn’t simply aim to improve upon its predecessors but establishes its own acoustic identity. The bass offers remarkable extension down to sub-bass frequencies, with articulation and impact superior to traditional electrostatics, while retaining the speed characteristic of this technology. This performance in the low register never compromises the clarity of the upper frequencies.

The midrange benefits from a slight warmth that favors the naturalness of voices and acoustic instruments, positioned between the more pronounced coloration of the SR-007 and the analytical neutrality of the SR-009S. The upper mids around 3 kHz can exhibit a slight prominence that some users prefer to tame via EQ, but this characteristic contributes to presence and instrument definition.

The treble extends smoothly up to 42 kHz, delivering exceptional resolution without ever tipping into harshness or aggressiveness. The soundstage reaches unprecedented dimensions for a STAX headphone, creating a three-dimensional space where each instrument occupies a distinct and stable position. This expanded spatialization directly results from the increased diaphragm surface area and the non-parallel enclosure design.

Technical Features

Main Specifications

• Type: open-back electrostatic headphones
• Transducers: 4-layer MLER-3 electrostatic
• Frequency response: 5 Hz – 42 kHz
• Sensitivity: 100 dB
• Impedance: 145 kΩ
• Electrostatic capacitance: 110 pF
• Bias voltage: 580 V DC
• Weight: 432 g

Transducer Technology

• Latest-generation MLER-3 electrostatic transducers
  • 4-layer electrodes (mesh + etched)
  • Optimal diaphragm control
• Diaphragm 20% larger than the SR-009S
  • Made from ultra-thin polymer film
  • Exceptional transient speed and precision
• Machined aluminum chassis
  • Eliminates unwanted vibrations
  • Clearer reproduction
• Non-parallel grille relative to the transducers
  • Controls sound reflections
  • Improved transparency
• Open-back design promoting airiness and soundstage

Sound Reproduction

• Deep, controlled bass with solid foundation
• Natural, detailed mids with rich harmonics
• Extended, finely sculpted treble without harshness
• Wide, immersive soundstage worthy of top-tier audiophile listening
• Exceptional musicality with pure, transparent, and dynamic reproduction

Comfort and Ergonomics

• Generous earcups with genuine sheepskin pads
  • Contact surface in genuine leather
  • Surround in synthetic leather
• Stainless steel headband with genuine leather strap
• Precise adjustment with 9-position clip system
• Lightweight design for long listening sessions without fatigue

Cabling and Connectivity

• Detachable low-capacitance cable
  • Ultra-pure 6N OFC copper conductors (99.9999%)
  • Annealed silver-plated copper conductors for better high-frequency transmission
• Two cables included: 1.5 m, 2.5 m
• STAX 5-pin connector
  • Compatible only with Stax amplifiers
  • Compatible with electrostatic headphone amplifiers

General Information

• Award-winning in the specialist press
• Supplied with a paulownia wood storage case
• Premium OFC copper and silver-plated copper cables included