STAX SR-009S Open-Back Electrostatic Headphones
In 2018 Stax celebrate 80 years as the pre-eminent manufacturer of Electrostatic audio products. Stax has established themselves as makers of the worlds finest Earspeakers (Headphones).
The ultra-thin diaphragm is made of super engineering plastic. The mass of the diaphragm itself is close to zero, ensuring excellent transient response. The ultra thinness of the diaphragm ensures colourations are kept to an absolute minimum. The push-pull electrostatic open-air diaphragm in the SR-009S has a frequency response from 5Hz to 42,00KHz. Unmatched by any moving coil diaphragm.
The SR-009S features an advanced cup design. The best cup is ‘no cup’ and lessons learned with the Stax SR-L700 Earspeaker, which featured a reduced number of bars on the rear of the cup, proved that the reduction of cup size and mass has noticeable benefits to the sound. The cup on the SR-009S is made of solid aluminium. The cup features thicker mounting points to secure the SR-009S diaphragm. Sound from the diaphragm is improved due to the solid mounting of the whole assembly. The thickness of the cup has been reduced to the bare minimum. In-turn reducing resonances and making the flow of acoustic sound waves smoother.
The SR-009S is an open-air design, where sound waves leave the rear of the cup. The sensitive diaphragm of the SR-009S need protection from the outside world.
The guard mesh on the SR-009S was re-examined. A new design which featured a curved surface was developed. The curve on the guard mesh gives increased rigidity and lowers resonance of the mesh. This in-turn ensures improved resolution and transparency of the sound. The new guard reduces the amount of contaminants entering the diaphragm, whilst at the same time improving the sound quality.
The cable of the SR-009S is a 6N Hybrid design. 6N Cu high-purity annealed copper wires are employed for the central cable. Six Silver plated annealed copper wires are arranged at the perimeter. The structure of the cable
utilises parallel conductors arranged in wide spacing. This spacing ensures low capacitance which is ideal for the higher voltages needed to run the electrostatic diaphragm. Reduction of capacitance also results in improved transparency and smoother high frequencies.
The ear cushions of the SR-009S have been improved. The highest quality of genuine leather is adopted for the material that touches the skin. High-quality artificial leather is used for the surrounding portion of the ear
cushion. Wearing comfort for long periods is improved by use of genuine leather. This material has good breathability and is more pliable, which ensures a good fit around the listener's ears. A good seal, minimises air leakage and in-turn improves bass response and low-frequency reproduction. As for the side pressure to the
ear, a dual-arc spring system has been adopted to realise both rigidity and flexibility. Like the SR-009, it automatically follows everyday head movement during listening.
The headband arc assembly features a 10 step click mechanism for height adjustment. The optimum feel and fit is obtained for different size heads, by precisely adjusting the step click mechanism. Once adjusted, the
optimal position of the arc assembly is maintained. Making it unnecessary to re-adjust the next time you use the SR-009S.
Paulownia wood has been adopted for the exclusive storage box
for the SR-009S. Paulownia is lightweight and is insect proof. It has antiseptic qualities and outstanding humidity rejection. Moreover, it features excellent fire-retardant qualities and offers low heat conduction. This attention to detail assures safe storage of the SR-009S over many years.
Type: push-pull electrostatic large circular sound element, open-air type enclosure
Frequency response: 5 - 42,000Hz
Electrostatic capacitance: 110pF (including cable)
Impedance: 145kΩ (including cable, at 10kHz)
Sound pressure sensitivity: 101dB / input 100Vr.m.s. / 1kHz
Bias voltage: DC580V
Right/left channel indication: Golden solid line (left) and dotted line (right) on the cable
Earpad: Genuine leather (skin touching portion), high-quality artificial leather (surrounding portion)
Cable: Silver-coated 6N (99.9999%) OFC parallel 6-strand, low-capacity special wide cable, 2.5m full length
Weight: 583g (including cable), 441g (without cable).