Astell&Kern XIO
Astell&Kern XIO, hybrid in-ear monitors
The result of a collaboration between Astell&Kern and 64 Audio, these in-ear monitors combine ten drivers per ear to cover the full audio spectrum. Handmade in the United States, they pair a 904L stainless steel shell coated with DLC with several patented acoustic technologies. The silver-plated single-crystal copper Litz cable ends in a balanced 4.4 mm jack, in keeping with recent Astell&Kern digital audio players.
A hybrid configuration with ten drivers
Each earpiece houses ten drivers distributed across four ways via an integrated passive crossover. Low frequencies rely on two dynamic drivers mounted in a TRUE ISOBARIC structure: the two motors work in perfect synchronization in an acoustically neutral coupling chamber. Bass reproduction gains density, depth, and impact on transients.
The midrange uses six balanced armature drivers, complemented by a seventh for the upper midrange. This generous sizing of the vocal and instrumental ranges favors warmth and clarity without narrowing the soundstage. High frequencies are handled by a direct-radiating tia driver, without an acoustic tube and paired with a custom waveguide to extend high-frequency response and preserve the sense of space.
On paper, the frequency response covers 5 Hz to 22 kHz, with a sensitivity of 103 dB SPL at 1 kHz for 1 mW and a low impedance of 6.3 ohms at 1 kHz.
Three patented technologies from 64 Audio
The tia (Tubeless In-Ear Audio) driver eliminates the acoustic tube that usually connects the diaphragm to the ear canal. This single-bore structure, paired with a dedicated acoustic chamber, reduces resonance and distortion at high frequencies.
The apex (Air Pressure Exchange) system regulates pressure in the ear canal while preserving passive isolation. This limits listening fatigue during long listening sessions and widens the soundstage compared with most closed-back in-ear monitors. The m15 module supplied with the XIO has been redesigned in 904L stainless steel coated with DLC, specific to this model.
The LID (Linear Impedance Design) circuit compensates for the non-linear resistance of balanced armature drivers. The sound signature remains stable, regardless of the output impedance of the source used: digital audio player, portable amplifier, or desktop DAC.
904L steel shell and DLC finish
The shell uses 904L stainless steel, an alloy usually reserved for watchmaking for its corrosion resistance and the quality of its polish. The DLC (Diamond-Like Carbon) coating gives it a deep black shade and good resistance to everyday scratches.
The faceplate features a three-dimensional pattern that echoes the visual language of Astell&Kern digital audio players, with angular facets that catch the light depending on the viewing angle. Inside, the layout brings together the tia waveguide, the balanced armature drivers, the TRUE ISOBARIC dual dynamic drivers, the apex module, and the 0.78 mm 2-pin connector.
Single-crystal copper Litz cable
The XIO comes with a silver-plated UP-OCC single-crystal copper Litz cable. Its four-core cross-braided structure limits interference between conductors and reduces microphonic noise. The termination uses the balanced 4.4 mm jack format, favored on recent hi-fi digital audio players for its superior signal-to-noise ratio compared with the unbalanced 3.5 mm jack. On the earpiece side, the 0.78 mm 2-pin connectors make recabling possible with compatible third-party accessories. Cable impedance is kept to 0.29 ohms.
Interchangeable apex modules and accessories
The package includes a 64 Audio leather case, three sets of ear tips (TrueFidelity foam, SpinFit silicone, and standard silicone, in sizes S, M, and L), a cleaning tool, a polishing cloth, and a cable clip.
Four interchangeable apex modules come with the earphones and allow adjustment of bass response and the sense of isolation: the silver m20 opens up the presentation further, the gold m12 sits in an intermediate position, the special XIO m15 in 904L stainless steel coated with DLC follows the same approach, and the black mX prioritizes bass foundation and external attenuation. They are changed by screwing them onto the acoustic outlet and alter the level of internal venting, which is felt mainly in the perceived pressure in the ear and the roundness of the low end.
Technical specifications
Overview
- High-end in-ear monitors developed through a collaboration between Astell&Kern and 64 Audio
- Handcrafted in the United States
- Designed as a true work of art combining aesthetics and acoustics
Acoustic system
- 10-driver hybrid configuration
- 2 dynamic bass drivers (TRUE ISOBARIC structure)
- 6 balanced armature drivers for the mids
- 1 balanced armature driver for the upper mids
- 1 tia balanced armature driver for the highs
- Integrated 4-way passive crossover
- TRUE ISOBARIC dual dynamic driver: two perfectly synchronized dynamic drivers in an acoustically neutral coupling chamber, delivering exceptionally deep and dense bass along with powerful sonic impact
- Balanced armature drivers: six drivers for the mids and one for the upper mids, reproducing vocals and instruments with warmth and clarity
- tia high-frequency driver: direct-radiating structure without an acoustic tube, combined with a custom waveguide, for airy, detailed highs and enhanced spaciousness
Audio specifications
- Frequency response: 5 Hz – 22 kHz
- Sound pressure level (SPL): 103 dB @ 1 kHz, 1 mW
- Impedance: 6.3 ohms @ 1 kHz
Proprietary technologies
- tia (Tubeless In-Ear Audio): patented design minimizing resonance and distortion through the tia driver, single-bore structure, and acoustic chamber, for clear and lively sound
- apex (Air Pressure Exchange): patented venting system that naturally releases pressure in the ear canal while maintaining excellent noise isolation, reducing listening fatigue and expanding the soundstage
- m15 module specially redesigned for the XIO, in 904L stainless steel with DLC coating, exclusive to this model
- LID (Linear Impedance Design): patented circuit compensating for non-linear resistance between the drivers, ensuring a stable sound signature and precise frequency response regardless of the source output impedance
Design and materials
- Precision-machined 904L stainless steel shell
- Black DLC (Diamond-Like Carbon) coating for a premium finish
- Faceplate with a three-dimensional design reflecting Astell&Kern’s stylistic heritage
- Internal structure integrating: tia waveguide, 0.78 mm 2-pin connector, DLC-coated 904L stainless steel shells, BA drivers for mids and upper mids, TRUE ISOBARIC dual dynamic driver, apex module, driver housing, and tia high-frequency driver
Cable
- Dedicated Litz cable in silver-plated UP-OCC single-crystal copper
- Four-wire cross-braided structure
- Connectors: 0.78 mm 2-pin
- Termination: 4.4 mm balanced jack
- Impedance: 0.29 Ω
- High-performance noise shielding and transparent signal transmission
Included accessories
- XIO universal in-ear monitors
- 64 Audio premium leather case
- TrueFidelity foam ear tips (S, M, L)
- SpinFit silicone ear tips (S, M, L)
- Silicone ear tips (S, M, L)
- Cleaning tool
- Cleaning cloth
- Cable clip
Frequently Asked Questions
Is the cable compatible with a standard 3.5 mm headphone output?
The supplied cable uses a balanced 4.4 mm jack termination, which is not directly compatible with an unbalanced 3.5 mm output. Passive 4.4 mm to 3.5 mm adapters do exist, but the balanced output then loses some of its benefits (channel separation, output level). Re-cabling with an equivalent cable terminated in 3.5 mm remains possible thanks to the standardized 0.78 mm 2-pin connectors.
Which Apex module should be used daily?
Astell&Kern and 64 Audio provide four modules to adjust internal pressure and bass fit. The m20 opens up the soundstage, the m12 and m15 occupy an intermediate position, and the mX boosts bass and isolation. The choice depends on the musical program, listening level, and tolerance threshold for pressure in the ear canal. Rotating between two modules depending on the usage context (transport, quiet listening at home) is a common approach.
Which source should you use to make the most of the XIO?
With its 6.3-ohm impedance and 103 dB sensitivity, the XIO only requires a low-noise source equipped with a clean 4.4 mm balanced output. An Astell&Kern digital audio player from the Kann, SP3000, or SR35 series provides this environment, as do some recent portable DAC/amps featuring the same output format.
Can the XIO be used as in-ear monitoring for the stage?
The universal shape and detachable Litz cable lend themselves to occasional stage use. For a professional musician seeking very high attenuation and extended comfort on tour, 64 Audio offers custom-molded shell models better suited to that context. The XIO remains above all a portable hi-fi earphone.
Is a break-in period necessary before critical listening?
Dynamic drivers with a TRUE ISOBARIC structure may experience changes in their mechanical compliance during the first hours of use. A few dozen hours of playback at moderate volume are enough to stabilize the behavior of the suspensions. Balanced armature drivers, on the other hand, are not subject to this phenomenon.
- Eco-contribution included in the sale price.
- GTIN / EAN: 8800309909071