64 Audio U12t VS ThieAudio Monarch MK4

The 64 Audio U12t lands exactly where its reputation suggests: a warm, laid-back, yet highly detailed all-rounder that stays engaging without ever turning fatiguing. With the apex M15 module, bass shifts toward a tasteful sub-bass lift that adds punch and body while keeping the midrange clean; vocals sit a touch relaxed, and the treble reaches high with smooth extension and air. Despite being an all-BA set, the low end carries surprising weight and macro-dynamics, and the overall presentation feels effortless and cohesive—“does-it-all” tuning done right.

Trade-offs are minor: timbre can sound slightly artificial at times, and dropping to the M10 module trims bass but also some excitement. Build is comfortable and compact, though the stock cable is annoyingly wiry and memory-prone. Against its stablemates, U12t stands as the benchmark: cleaner and less fatiguing than U18t, more versatile than the warmer Nio (with M15), and less head-stage wow than Trio but more universally balanced. End result: a confident 5/5 for a high-price IEM that actually feels worth chasing if this signature hits the brief.

Super* Review original ranking

ThieAudio Monarch MK4 comes in at $1,150 with a tribrid array—2 DD + 6 BA + 2 EST—a chunky stock cable with friction-fit swappable terminations, and a genuinely excellent, in-ear-operable “Rumble” bass switch. The new metal shells look tidy, but the fit is very large; on average ears it tends to sit a bit out of the concha and feel unstable (seal is doable, comfort is mediocre). Build details like the firm chin slider are nice, yet the cable bulk and loose termination retention detract from daily use.

Tonally, stock MK4 aims for a clean-neutral presentation with a meaty, sub-bass-focused lift, lively upper registers, and excellent extension. The flip side is a slightly dry / clinical character with a hint of treble hardness that can leave notes feeling a bit bodyless. Engaging Rumble mode thickens the curve from ~300 Hz down—more warmth and weight, bordering on “gigabass” territory—making the set fuller and more fun, though arguably too bassy for purists. Staging and imaging are solid, and resolution is high, but macro-dynamics land behind peers; compared side-by-side, sets like Dunu Glacier and 64 Audio U4S feel punchier, while Valhalla sounds warmer, smoother, and more effortlessly resolving.

Overall, MK4 is a technically capable tribrid with two distinct tunings on tap—clinical-clean stock and warmed-up Rumble—but it’s held back by fit size, cable quirks, and that slightly wooden bass texture. For listeners chasing a bright-leaning neutral with legit sub-bass reach (and who can accommodate a big shell), it’s a compelling try; in this lineup, though, it settles at a three-star recommendation next to more engaging or comfortable alternatives.

Super* Review original ranking

The ThieAudio Monarch MK4 presents a well-extended, refined treble that measures cleanly and feels more polished than earlier iterations, though the overall tonality can read a touch thin. Against its sibling Valaha, the MK4 trades warmth for a clearer top end, keeping the presentation crisp without obvious harshness.

Between the pair, the MK4 takes the edge on technical performance—notably resolution—thanks to a bit more upper-treble energy and a more controlled bass shelf, while the Valaha offers extra mid-bass thump and a slightly warmer tilt. Net result: the Monarch MK4 remains a standout around $1,000, balancing precision and extension better than its stablemate.

Precogvision original ranking

The Thieaudio Monarch MK IV presents two distinct tuning options, elevating its versatility. The balanced switch delivers a clean, smooth, and slightly airy presentation, offering a refined all-rounder sound that's very detailed, well-layered, and resolving – essentially a direct upgrade to predecessors like the Monarch MK3 and Top Pro, with slightly more treble detail and air. Conversely, the bass switch provides a significantly fuller, warmer low end with punchy, well-textured bass and a tamer upper midrange, addressing criticisms of thinness in earlier models and offering a specialized, engaging listen for bass-heavy genres.

Technically, the MK IV sits comfortably in the $1,000 tier, offering a slight bump in detail retrieval, refinement, and smoothness over the MK3 and MK2, comparable to the Dunu Glacier and Prestige LTD. While not a giant leap, the dual tuning options make it arguably a better all-rounder than single-tuning competitors; the balance switch excels with acoustic, classical, and cleaner genres, while the bass switch shines with rock, metal, R&B, and pop. Build quality is improved with an all-metal shell, though the flimsy cardboard case is a notable disappointment. Vocals are smooth, balanced, and enjoyable, though sets like the Monarch MK2, Mystic 8, RSV, or Arcanis offer more forwardness or unique character. Bass quality is excellent for most, though pure bass enthusiasts might prefer models like the Thieaudio Origin for its unique texture.

Ultimately, the Monarch MK IV is a highly compelling endgame option for the vast majority. It combines strong technical performance with exceptional versatility through its two excellent tunings, covering a wide genre spectrum effectively. While value-focused options like the Top Pro, Volare, or Mega5EST offer similar technicalities at lower prices, the MK IV's refinement, tuning flexibility, and slightly superior performance make it easy to recommend. It allows listeners to leave the hobby satisfied, provided they resonate with its sound – though chasing marginally better flagships involves steep diminishing returns. The king might be debatable, but the MK IV is undoubtedly a very solid $1,000 contender.

Jays Audio original ranking

Priced between $1,150 and $1,300 depending on custom faceplate options like the butterfly design shown, the Thieaudio Monarch MK IV boasts exceptional build quality with a large but well-contoured titanium shell offering a secure and comfortable fit. Key features include the innovative rumble switch for adjustable bass levels on the fly, a durable two-pin connector, and a solid feel that inspires confidence in longevity. While the included accessories are considered fair but unexciting, the shell's customization potential and rugged construction are major highlights.

Sonically, the Monarch MK IV delivers a detailed, exciting, and clean sound signature that stands as the best in the Monarch lineage. The rumble switch provides two distinct profiles: the red switch (no rumble) offers a balanced, tactful bass presentation, while the gold switch (rumble) adds a satisfying sub-bass shelf ideal for genres like hip-hop. Treble performance is notably improved over the MK III, though a 10k peak requires careful ear tip selection for some listeners. It trades blows with flagships like the $3,000 Annihilator (better sub-bass focus) and the $1,800 Elysian Apostle (more vocal forward), often matching or exceeding their technicalities while offering its unique tuning flexibility.

Scoring a top-tier 9.8, the Monarch MK IV earns its place through a compelling combination of premium build, the highly functional rumble switch, and outstanding sound quality that feels both special and refined. While acknowledging the high price, it represents significant value against competitors like the $2,000 Thieaudio Valhalla or the fiddly Grand Maestro, offering a feature-rich, durable, and sonically excellent package that justifies its position as a current summit-fi favorite.

Jaytiss original ranking

ThieAudio Monarch MK4 arrives with the usual hype and a clear step-up in presentation: a thick, high-quality premium cable with interchangeable terminations, plenty of tips and tools, and a handsome case. The shells move to an all-metal build with a resin faceplate and a bass switch, while the internals stack up to 2DD + 6BA + 2EST in a four-way crossover. It is a big set—more long than wide—so smaller ears should test fit first, but the overall finish and hardware feel decidedly upscale.

In quick listens, the normal mode is the sweet spot: clean, powerful and immediately great without obvious quirks. Flipping the switch to bass mode turns things thunderous—fun for a moment—yet can nudge vocals out of balance on bass-heavy tracks, making the standard setting the better choice for everyday use. Early take: a confident, polished evolution of the Monarch line that favors balance and refinement in normal mode, with optional low-end excess on tap for those chasing extra rumble.

Tim Tuned original ranking

The ThieAudio Monarch MK4 is a premium IEM that earns a spot in the S-tier for competitive gaming, offering a significant upgrade over its predecessor and A-tier competitors. It features a unique rumble mode switch that adds a satisfying low-end punch and weight without muddying the detailed, reference-grade tuning of the standard mode. While the CNC aluminum build feels exceptional, the design is a bit bulky and heavy, which can lead to some comfort issues during very long, multi-hour sessions.

For gaming, the technical performance is nothing short of phenomenal. The imaging is holographic and the depth perception is absolutely exceptional, providing a critical advantage in tactical shooters like VALORANT where tracking footsteps through walls becomes incredibly precise. The wide and deep soundstage pushes sounds off the player, creating an immersive experience. While rumble mode is preferred for titles like Call of Duty, the standard mode's clean and detailed signature shines in battle royales like Apex Legends, though the 2-4k range can make gunfire a bit shouty at higher volumes.

This is also an absolutely amazing set for music, delivering an elevated level of technicality and resolution. The standard mode offers a fast, clean, and neutral listen with great detail retrieval, while the rumble mode provides a weightier, more engaging bass profile for tracks that benefit from the extra warmth and punch. Ultimately, it's a very high-end IEM that delivers a top-tier experience for both competitive gaming and critical music listening.

Fresh Reviews original ranking

Monarch MK IV lands as a top-three set, sitting just behind the PMG APXSE and CP622B, and it earns that spot with an evolutionary design: a single, tactile rumble switch that can be flipped while the IEM is in-ear—no fiddly pins, no tools. In stock (red) mode it’s a vocal-friendly tuning with restrained mid-bass; engage the switch and the low end lifts, adding note weight without smearing the mids. The shell is metal, build is tight, and all the BAs are Sonion, signaling premium parts and execution.

Low-end performance nails both 808 drops and classic rock kick drums (“When the Levee Breaks”) with satisfying slam—better with the switch on—while bass guitar texture (pulls, plucks, string ring) stays articulate into the lower treble. Vocals are clean in stock mode and gain a pleasing husk and density with rumble engaged, making artists like Neil Young and Mark Knopfler pop. Upper mids/treble avoid glare and long-term fatigue, turning this into a true “sofa set” for hours-long sessions.

At $1,400 it competes shockingly well against far pricier summit-fi gear—no veil, no masking, just balanced resolution and a flip-to-taste bass shelf. Compared to Valhalla, the MK IV’s instant two-flavor flexibility pushes it ahead on value; bone-conduction curios like Origin feel more niche by contrast. Net: the best ThieAudio to date, an easy recommendation, and likely the new #3 overall—thanks to that simple, game-changing rumble switch that future proofs the tuning.

Bad Guy Good Audio original ranking