Astell&Kern x 64 Audio XIO In‑Ear Monitors

Hear the whole recording, not just the highlights

XIO turns the “in‑ear compromise” on its head. If you’re tired of congested soundstages, boomy bass, or treble that gets fatiguing, these flagship monitors deliver an expansive, three‑dimensional presentation with bass depth and control, lifelike mids, and airy, grain‑free highs—all in a compact, all‑day‑wearable design. They’re engineered to keep the sound stable across different sources, relieve ear‑canal pressure for comfort, and wrap it all in a luxury shell that feels as exceptional as it sounds.

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Why Audiophiles Choose This Product

• Bold, spacious sound with grip and control: A 10‑driver hybrid array anchored by a TRUE ISOBARIC dual‑dynamic bass system delivers deep, dense low end without muddying the mids; a tia high‑frequency driver and waveguide keep treble open and effortless. The result is a large, layered stage with precise imaging.
• Cutting‑edge acoustic engineering: 64 Audio’s patented trio—tia (tubeless high driver), apex (air‑pressure relief), and LID (Linear Impedance Design)—work together to minimize resonance and fatigue, maintain tonal accuracy across sources, and let you listen longer with less pressure build‑up.
• Luxury materials, built to last: Precision‑milled 904L stainless steel—finished in a black DLC coating—offers watch‑grade hardness and corrosion resistance with a distinctive Astell&Kern faceted aesthetic. Hand‑assembled in the USA by 64 Audio.
• Real‑world versatility: A low‑impedance, 4.4 mm balanced, silver‑plated UP‑OCC Litz cable (0.78 mm 2‑pin) pairs cleanly with modern DAPs and balanced dongles; LID keeps the tuning consistent even when output impedance varies between devices.
• Tune it your way: Four interchangeable apex modules (m15, m20, m12, mX) ship in the box, letting you gently shape isolation and tonal balance—from thicker, weightier bass to a leaner, airier presentation—without EQ. Independent reviewers highlight the audible differences between modules.

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What’s Included

• XIO Universal In‑Ear Monitors — 10‑driver hybrid: 2 × low DD (TRUE ISOBARIC), 6 × mid BA, 1 × high‑mid BA, 1 × tia high BA; integrated 4‑way passive crossover.
• 4.4 mm balanced silver‑plated UP‑OCC copper Litz cable — 0.78 mm 2‑pin; cross‑braided, low 0.29 Ω cable impedance for excellent noise rejection and electrical efficiency.
• Ear tip kit — TrueFidelity foam (S/M/L), SpinFit silicone (S/M/L), standard silicone (S/M/L).
• 64 Audio premium leather case, cleaning tool, cable clip, cleaning cloth.
• apex modules — m20 (Silver), special m15 (904L DLC), m12 (Gold), mX (Black).

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Technical Specifications

Specification	Value	Notes
Product Type	Wired in‑ear monitors	0.78 mm 2‑pin IEMs with 4.4 mm balanced cable.
Driver system	10‑driver hybrid	2 × low dynamic (TRUE ISOBARIC), 6 × mid BA, 1 × high‑mid BA, 1 × tia high BA.
Crossover	4‑way passive	Smooth band integration; coherent imaging.
Frequency response	5 Hz – 22 kHz	Extended bandwidth for sub‑bass reach and airy highs.
Sensitivity	103 dB @ 1 kHz, 1 mW	Easy to drive; scales with high‑quality sources.
Impedance	6.3 Ω @ 1 kHz	LID keeps tonal balance consistent across source impedances.
Shell	904L stainless steel with black DLC	Watch‑grade hardness and premium finish.
Cable	4‑core silver‑plated UP‑OCC copper Litz	0.29 Ω cable impedance; 4.4 mm balanced termination.
Pressure relief	apex modules (m15/m20/m12/mX)	Tailor isolation and tone without EQ.
Connection	0.78 mm 2‑pin (IEM side)	Wide aftermarket cable compatibility.
Weight	Not specified	Manufacturer has not published weight at time of writing.

Specifications verified from the official Astell&Kern XIO product page and corroborated by authorized retailers.

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Professional Recognition

• Media coverage: “new high‑end IEMs deliver 10‑driver delight,” noted T3, highlighting the hybrid driver array and premium build.
• Industry press: Yahoo Tech underscored XIO’s trio of 64 Audio technologies—tia, LID, and apex—plus the 904L/DLC chassis and custom cable.
• Review highlights: Hong Kong outlet SPILL praised XIO’s “open, expansive soundstage” and showed how the four apex modules offer clearly different voicings in practice. Post76’s first‑listen echoed the module‑by‑module tonal shifts and applauded comfort and isolation.
• Heritage: Co‑developed by Astell&Kern and 64 Audio; each unit is handcrafted in the USA, reflecting 64 Audio’s pro‑monitor roots and A&K’s sculptural design language.

Short quotes are used for identification and fall under fair use.

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The Bottom Line

XIO is for listeners who want reference‑grade resolution without losing musical weight and scale. Its TRUE ISOBARIC bass system delivers impact with discipline; tia highs add air without glare; and apex keeps you comfortable and engaged for marathon sessions. With a luxury 904L/DLC chassis, balanced UP‑OCC cable, and four apex modules included, you’re buying not just a flagship sound, but a complete, adaptable system that feels every bit as premium as it looks. If you’ve been chasing “big‑speaker space” from an IEM, this collaboration lands it—beautifully and reliably—across the sources you already own.

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Notes for headphone buyers

• Connectivity: wired, 0.78 mm 2‑pin, 4.4 mm balanced termination. Use appropriate adapters or cables for 3.5 mm or 2.5 mm outputs.
• Sound signature: expansive stage, dense and controlled bass, clear mids, airy and refined treble; apex modules let you tailor the emphasis from warmer/richer (m15) to leaner/flatter (mX).
• Comfort: apex relieves ear pressure; multiple tip options optimize seal and long‑session comfort.

If you want a flagship IEM that blends art‑grade build with studio‑caliber engineering, XIO belongs on your shortlist.