Though founded in 1938, it would take STAX another 21 years to invent the first of the products for which they would receive critical acclaim and eventually achieve global recognition. In 1959 the company developed the world’s first electrostatic headphone, culminating in the introduction of the R1 in 1960. These are no ordinary headphones – referred to instead as “ear speakers”, as the company would rather you compare their technology to that of cost-no-object loudspeakers rather than competing headphones.
The STAX portfolio now includes a range of models for consumer and professional use along with the required electrostatic amplifiers, several replacement parts and even a headphone stand. Several companies still manufacture replacement parts for the original STAX models, many of which remain in use today.
Ownership of STAX was taken over by Edifier in 2012. Edifier is a Chinese company also responsible for the AirPulse brand, as well as a vast product portfolio under their own name. Their products blend the latest in acoustic design and digital hardware, traditional craftsmanship and trickled-down technology to achieve price points that others simply cannot match. It’s no surprise then that there’s a new STAX product in the game, though you won’t find it listed on the STAX website. The STAX Spirit S3 is a radical departure from anything STAX has produced before, and would I’m sure break the hearts of the STAX purist. Let’s take a look.
The S3s are supplied in typically stylish Edifier packaging. THey’re provided in a hard shell carry case in which are the headphones themselves, USB C and AUX cables and some basic instructions. You get a quarter inch adapter and a plastic spudger tool, which is used to remove the ear cushions by sliding it in the gap between the frame of the ear cushion and the ear cup and prying the ear cushion off. I’m sure Edifier could have devised a more elegant way to swap the pads, and I wouldn’t want to swap them too often for fear of breaking the clips that hold them in place.
A second set of ear cushions are packed with the headphones. These are a cooling mesh design that allow more airflow than the lambskin leather pads that come fitted as standard. Swapping them is easy, and there’s a configuration setting in the app to alter the sound to suit the different material – more on that later.
Build quality is excellent, though there’s a little more plastic in the sliding mechanism and headband than I would like. The headphones fold to fit their case and rotate approximately 60 degrees in each direction for comfort. The mechanisms feel like they’ll last, and the hard case will reduce the changes of travel damage.
Comfort too is excellent. The cushions fit my ears perfectly, surrounding them with lambskin leather bliss. The mesh cushions are equally comfortable and improve airflow around the ears at the slight expense of sound isolation and leakage. The lambskin cushions are the clear winner for home use, and the mesh pads are better suited to travelling and use on the go, in hotter environments or if you naturally sweat a lot.
The S3s aren’t actually electrostatic. They are in fact planar-magnetic headphones, which comprise a driver with an ultra-thin diaphragm onto which are printed flat wire coils, suspended between magnets. The design of a planar-magnetic driver allows for exceptional control under the right conditions, as well as better dynamics, clarity and lower distortion than a dynamic driver.
A typical dynamic driver consists of a cone, usually circular, which is attached to a coil of wire known as the voice-coil. A magnetic field is created when the voice-coil is energised by the amplifier, reacting with the magnet of the driver to cause the cone to move pistonicly (in and out) in a rapid linear motion. In doing so vibrations are caused on the surface of the cone and hence sound is reproduced, but there are also small deformations caused on the cone surface too known as cone breakup. Cone breakup occurs as the driver is required to handle a more complex signal, and is especially problematic at low frequencies. The result is increased distortion and a tendency to blur other parts of the frequency spectrum, especially in the case of a headphone where usually only a single driver is reproducing the music, known as ‘full range’.
Planar drivers differ in that their entire surface is intended to move and vibrate in a controlled manner. But unlike a typical Planar driver, the drivers of the Spirit S3 have some additional features. The drivers technology comes from and are used under license from Audeze, a California-based company famous for their planar-magnetic headphones.
Uniforce is designed to deliver a uniform driving force (I.E driving towage) across the surface of the driver, giving a more accurate reproduction of the audio waveform and keeping distortion to just 0.5%.
Audeze Fluxor™ magnetic structure technology and the use of neodymium magnets with double the flux density of traditional magnets increase efficiency, which gives a greater sound pressure or higher output volume for a given power. The magnet structors are designed such that the sound waves produced by the movement of the diaphragm are unobstructed for the cleanest possible reproduction.
The A-Weighted sound pressure level is specified at 94±3dB (A) from a 24Ω, 89mm*70mm planar-magnetic driver. Frequency response extends from 20Hz to 40kHz, though no linearity figures are offered. There is a single 3.50X2.65X0.98mm internal microphone with a rated sensitivity of -37dBFS±1dBFS used for phone and video calls and control of a voice assistant.
The S3 supports the latest Bluetooth 5.2 audio technology with A2DP, HFP and AVRCP for device control. The S3s support high-res audio including AptX Adaptive, AptX (16-bit, 44.1kHz), AptX Voice (up to 32kHz audio quality) and AptX HD (24-bit, 48kHz lossless) and Snapdragon Sound with supported devices. Bluetooth transmission distance is 10 metres.
The S3s can be connected to two Bluetooth devices simultaneously. This is useful if, for example you use them at a desk with a laptop, but you also want to have them paired with a smartphone to receive calls or receive audible notifications. The dual pairing process is a bit fiddly and its performance is not seamless. You first pair a device (device A) and then disable Bluetooth on that device, allowing device B to be paired. Then you re-enable Bluetooth on device A and reconnect to the headphones. Device A takes priority. If you have music playing on device A, for example, and device B wants to play sound, you’ll hear nothing. If you have music playing on device B, however, and device A wants to play a sound, the sound from device B will be interrupted. The transition between devices takes a few seconds. If you prefer a wired connection there’s a 3.5 mm audio input and a cable included in the case with a 6.3 mm (quarter inch) adapter if you need it.
The S3s are controlled by the Edifier Connect app, available free from the iOS app Store or Google Play store. Edifier connect allows you to change the headphone equalisation depending on which ear cushions you’re using, as well a switching between equalisation profiles. You get three controls on the headphones themselves that all perform several functions. The volume up and down buttons double up as next / previous track controls when held for a couple of seconds. Hold both together for 6 seconds and you’ll perform a factory reset and enter pairing mode.
The centre button can be configured to perform several functions including play / pause, changing the sound mode, enabling game mode and launching your phone’s voice assistant. Further more these functions can be assigned to single, double or triple clicks of the button for even greater versatility. This button doubles up as the power button when held for around 7 seconds.
There are 3 sound modes to choose from. Hi-fi appears to be a flatter response, though I felt it had a slight lower midband boost. Classic mode is the default and is the typical recessed midband and slightly elevated base, though not to the extent of Beats or Bose. The classic mode was my preferred mode, as it gives the S3s a dynamic, lively sound that is tremendous fun.
STAX mode aims to simulate the sound of STAX ear speakers. It’s mostly flat, though with a slight upper midband boost that to my ear gives it a slightly unwelcome harsh quality to its sound. I’d rather that then a lower midband boost though, so it was my secondary preference in terms of the three modes available. It would be nice to see the ability to create your own sound mode, perhaps with a multi-band equaliser.
There is no active noise cancelling, though the ear cushions do a fine job of isolating background noise and keeping your music contained, even at high volume. You do get a low-latency ‘game mode’ though, which noticeably reduces latency at the expense of some battery power.
Though given that the S3s pack a 1500mAh battery, and can run for an impressive 80 hours of playback on a single charge, battery life is hardly an issue. Total charge time is around 1.5 hours, but a little over 10 minutes on the charger gets you 11 hours of play time with game mode switched off. The headphones charge via USB C, for which a USB C to USB A cable is included. The battery is contained within the left ear cup and is sadly not easily replaceable. The ear cup is screwed together but the screws are covered in a layer of adhesive. It would I’m sure be possible to fit another battery, but you will void your warranty and you’ll need a level of technical and mechanical intuition.
I’ve used the S3s with all kinds of music from rock to pop, from jazz to classical and everything in between. I’ve used them to enjoy podcasts while I’m working and used them to watch TV shows and a movie or two. I took them traveling on a recent trip to see the Bat Out Of Hell UK tour, where they made the car journey infinitely more bearable. In every case they’ve proven themselves to be highly versatile performers with excellent sound. I’ve used them with an iPhone 12 Pro and a MacBook Pro 16 inch and experienced no dropouts with either. I tend to keep them in game mode for the low latency performance and have charged them only once despite playing them at high volume for hours on end. The battery life on these things is simply phenomenal.
The Spirit S3 are not earspeakers for the STAX purist. They’re cutting-edge Bluetooth headphones for the wifi generation, packing some of the best tech currently available anywhere. They support the very latest wireless codecs and connectivity standards, offer outstanding comfort, portability and battery life, and at their heart are some of the best planar-magnetic headphone drivers on the market. They may not be pure STAX, but they’re worthy of the STAX name through and through. Highly recommended.
