Thieaudio Monarch Mk2 VS 64 Audio U4S

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Build & fit: Premium presentation with a handsome “lava” faceplate and a cloth-sheathed cable featuring swappable terminations—useful, but the connector is bulky enough to be unwieldy. The shell itself is very large and can be tricky for many ears, affecting seal and even bass response. Comfort and security are not strong suits. Tip rolling helps; AZLA AirFit Light tips improved seal and tamed occasional treble bite.

Sound: A neutral, mid-forward tuning with a tasteful sub-bass lift, clean lower treble, and excellent extension. Midrange detail pops with fine micro-contrast, while treble remains smooth—evoking that easy, HD600-like effortlessness. Stage is wide with standout imaging and layering. The trade-off is a lean lower-mid/mid-bass region (that “Harman dip”), which can make non-bass-heavy music feel a bit dry and clinical, reducing perceived depth and visceral impact.

Comparisons & verdict: Versus Moondrop’s stable, Blessing 2 still offers a fuller, more linear low end and remains the more all-round pick; S8 brings superb treble and mid detail with similarly lean bass; Campfire Aura dazzles with holographic imaging and surprisingly satisfying BA bass, though its tonality is quirkier. Monarch MKII earns a solid 4/5 for tonal balance, resolution, and imaging—but the size/fit caveat is serious, and the lean bass means it won’t dethrone Blessing 2 for those craving warmth or body. Demo first; if it fits and that crisp neutrality appeals, it’s a fantastic listen.

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The 64 Audio U4s hits a compelling sweet spot: a 1DD+3BA hybrid around $1,100 that echoes the lush, bass-tilted character of the Nio while fixing key drawbacks. Packaging and accessories feel improved, with multiple tip options and the included M12 APEX module; APEX not only tailors bass but also relieves pressure for long sessions. Fit follows 64 Audio’s comfortable triangular shell; the vented DD asks for a slightly shallower insert than the all-BA models. Sonically, expect a sub-bass-oriented shelf and a treble profile that’s more lively and “zingy” than the Nio, with extra energy around the upper treble. The big caveat is 64 Audio’s muted 2–4 kHz region, which can set soprano vocals a step back on the stage.

Against the brand’s full-BA staples (think U12t/U6t), the U4s trades some pinpoint imaging and coherency for unmistakable DD slam and tactile “air pushing.” Extension at both ends is excellent, with upper-treble energy that makes micro-detail and reverb trails pop. It’s not the clean, conventional neutrality of something like a Monarch-style tuning; rather, it’s a deliberate, colored signature that delivers fun plus technical chops. Crucially, it fills a missing niche at its price and, in many respects, outperforms the pricier Nio, making the U4s a standout recommendation for listeners who want bass authority, sparkle, and engaging dynamics without going all-in on the flagship tier.

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Build & accessories: Compact shell with a slightly old-school shape and flat 2-pin connectors, secure fit, and a nozzle some may find a bit much. The package includes Thieaudio’s large, sturdy case, multiple tips, a cleaning brush, and a fabric-sheathed stock cable with a solid chin slider and a durable Y-split. The cable’s modular plug system (2.5/3.5/4.4) locks in confidently and feels well made.

Sound: a neutral foundation with a dash of fun—clean upper mids, tasteful sparkle, and tight, articulate bass. Unit variance shows on graphs (his sample reads a bit bassier with slightly more treble vs other measurements), but the core tuning stays intact: rich mids, smooth presence, and airy extension that present music as natural, wide, and open. Versus Monarch MKIII, this MKII feels less bright and less fatiguing, with fuller mids. Compared to Annihilator 2023, MKII is flatter and more even (Annihilator hits harder and has a 10k zing some hear as “fake”). Against Lime Ears Tera, MKII is a touch warmer and easier; versus the pricier Europa, it tracks similarly on paper but wins on comfort and value; and it offers more body than budget darlings like Hexa, which can come off lean.

Verdict: a high-tier all-rounder prized for midrange timbre, air/detail, note weight, and imaging. It reads neutral-natural with just enough excitement to stay engaging over long sessions. Personal taste and fit still matter—always demo if possible—but within this preference space, Monarch MKII remains a special, well-balanced choice that continues to earn its spot among top IEMs.

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The 64 Audio U4s hits a compelling sweet spot: a 1DD+3BA hybrid around $1,100 that echoes the lush, bass-tilted character of the Nio while fixing key drawbacks. Packaging and accessories feel improved, with multiple tip options and the included M12 APEX module; APEX not only tailors bass but also relieves pressure for long sessions. Fit follows 64 Audio’s comfortable triangular shell; the vented DD asks for a slightly shallower insert than the all-BA models. Sonically, expect a sub-bass-oriented shelf and a treble profile that’s more lively and “zingy” than the Nio, with extra energy around the upper treble. The big caveat is 64 Audio’s muted 2–4 kHz region, which can set soprano vocals a step back on the stage.

Against the brand’s full-BA staples (think U12t/U6t), the U4s trades some pinpoint imaging and coherency for unmistakable DD slam and tactile “air pushing.” Extension at both ends is excellent, with upper-treble energy that makes micro-detail and reverb trails pop. It’s not the clean, conventional neutrality of something like a Monarch-style tuning; rather, it’s a deliberate, colored signature that delivers fun plus technical chops. Crucially, it fills a missing niche at its price and, in many respects, outperforms the pricier Nio, making the U4s a standout recommendation for listeners who want bass authority, sparkle, and engaging dynamics without going all-in on the flagship tier.

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Thieaudio Monarch Mk2 stays a top-tier pick by balancing excellent tonality with solid, price-appropriate technicalities. The tuning sits close to the current meta, with a slight dip in the lower mids and a noticeable 6 kHz emphasis that adds sparkle and energy. It’s the “spice” to the Mega5-EST’s plain water—still coherent and controlled, but with extra fizz that makes music feel lively. While resolution doesn’t chase the extremes of Elysian Annihilator or Softears RS10, within the $999 bracket the performance remains compelling, making it an easy recommendation among kilobuck IEMs.

Build and accessories are straightforward: a full-resin shell with metal nozzle, a cloth-sheathed cable featuring interchangeable 3.5 / 2.5 / 4.4 terminations, and a proper case with silicone and foam tips. The fiery orange faceplate is the sole colorway. The catch is fit—the shell is large, and for smaller ears that can be a deal-breaker; no sound quality matters if it won’t seal comfortably. For those wanting a near-perfect meta hit with less treble spice, Hisenior Mega5-EST is noted as the safer tonal bullseye.

Choose Monarch Mk2 if a slightly V-leaning, meta-aligned tuning with engaging upper-presence appeals, and if the ear geometry can handle the chunky shell. Skip it if chasing max detail retrieval above all else, craving a more pronounced V-shape (consider Monarch Mk3 instead), or if fit is uncertain. The overall verdict: impeccable tuning paired with good—if not summit—technical chops keeps Monarch Mk2 at the top of the ranking conversation without needing boutique pricing.