In-Ear MonitorOverreview

THIEAUDIO Monarch MKIV

A flagship do-everything tribrid with a two-in-one tuning switch — technically stunning, and quietly one of ThieAudio's most polarizing sets.

13 sourcesUpdated
$1,149Typical US price

Score aggregates reviewer opinions across topics.

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THIEAUDIO Monarch MKIV

The short version

What to know.

A $1,149 flagship tribrid IEM (two 8 mm IMPACT² dynamic drivers, six Sonion balanced armatures and two Sonion electrostatic tweeters per side, 4-way crossover) and the first Monarch with a STANDARD/RUMBLE tuning switch. Reviewers broadly agree on the core strengths: reference-grade resolution and detail for the price (a point even its harshest critic concedes), a wide, holographic soundstage with precise imaging, a standout CNC T6-aluminum build, easy drivability (≈10 Ω / 100 dB — happy off a phone dongle), and a genuinely useful switch that adds about 3 dB of sub-bass on demand. Where they split — and this is a polarizing set (RedditRecs 59% positive) — is on almost everything about its character: whether it's a warm, versatile all-rounder or a neutral-bright, revealing set that isn't the 'warm' IEM some expect; whether the standard-mode bass is clean and fast or lean and unremarkable (and rumble mode fun or a touch overbearing); whether the natural midrange is a highlight or, to one prominent critic, 'dry and sterile'; whether the extended treble is airy detail or hot and fatiguing; and whether the large shell and thick 6.3 mm nozzle fit at all — its size is the single most common complaint. Value is contested too: a legitimate kilobuck endgame to some, hard to justify to others now that $120–300 sets get close. A tip swap, the RUMBLE switch and a slightly warm source are how most owners settle its brighter, leaner edges.

About this product

The 2025 fourth-generation Monarch — a 2DD + 6BA + 2EST tribrid (two 8 mm IMPACT² dynamic drivers, six Sonion balanced armatures, two Sonion electrostatic tweeters, 4-way crossover) and the first Monarch with a STANDARD/RUMBLE tuning switch. Not the outgoing Monarch MKIII or the classic Monarch MKII (different drivers and tuning, and no switch on the older sets), and not ThieAudio's pricier Valhalla or V16 Divinity flagships. It shares its IMPACT² subwoofer with the far cheaper Hype series but adds the BA/EST array and the metal shell.

The THIEAUDIO Monarch MKIV is the $1,149 fourth-generation Monarch — the flagship all-rounder of ThieAudio, the in-house brand of retailer Linsoul. It's a ten-driver tribrid per side (two 8 mm IMPACT² dynamic drivers, six Sonion balanced armatures and two Sonion electrostatic tweeters, on a 4-way crossover), wrapped in a CNC-machined T6-aluminum shell — and, for the first time in the line, it carries a hardware tuning switch that flips between a studio-neutral STANDARD mode and a bassier RUMBLE mode. It's the set the far cheaper Hype series has been chasing.

The Monarch has spent years as a default 'endgame all-rounder' recommendation, and the MKIV keeps most of that reputation: near-universal praise for its resolution, soundstage, build and the versatility of the switch. But it is genuinely divisive — only about three in five Reddit owners rate it positively. The arguments aren't about whether it's competent; they're about its character. Is it a warm, versatile all-rounder or a leaner, brighter, more revealing set than the 'warm' IEM many expect? Is the extended treble airy detail or simply too hot? Does the big metal shell even fit? And is a kilobuck worth it now that $120–300 sets get so close? Plenty of praise to average, and a real fault line to map.

A good fit for

  • Detail and technical listeners who want resolution, air, a wide stage and precise imaging over outright warmth
  • Buyers who want one versatile all-rounder for every genre — with a switch to go from neutral to basshead
  • Owners who'll actually use the RUMBLE switch, which turns the neutral tuning warm and punchy on demand
  • Listeners upgrading from mid-fi who want a clear step up in resolution, stage and build
  • People who want flagship-tier tribrid sound they can drive straight off a phone dongle or DAP

Think twice if

  • You have smaller ears or want all-day comfort — the shell is large and the 6.3 mm nozzle is chunky (demo first)
  • You're treble-sensitive or listen loud — the extended top end can turn hot or fatiguing
  • You want a warm, laid-back, forgiving tuning — in STANDARD it's neutral-bright and unforgiving of poor recordings
  • You're price-sensitive — many feel $120–300 sets now get you most of the way, and this is the first Monarch to raise the price
  • You want basshead slam in the default tuning — STANDARD is deliberately lean in the mid-bass, so lean on RUMBLE

The reviewer consensus

Agreement &
disagreement.

6 / 12topics divide opinion
detailsoundstageimagingdynamicsbuildtonalitybassmidstreblecomfortvalueisolation
1 Strong agreement4 Mostly agree6 Divided opinions1 Limited evidence

Common ground5

  • Reference-grade resolution and detail for a kilobuck — clean and consistent, a strength even the critics concede.
  • A wide, deep, holographic soundstage with precise imaging and separation — repeatedly singled out as a highlight.
  • A genuinely useful tuning switch (STANDARD ↔ RUMBLE) that adds about 3 dB of sub-bass on demand — praised as two tunings in one.

Points of contention6

  • Tonality: a warm, versatile all-rounder vs a neutral-bright, revealing, energetic set that isn't the 'warm' IEM some expect.
  • Bass: deep, clean and versatile via the switch vs lean and unremarkable in STANDARD (or a touch overbearing in RUMBLE).
  • Mids: natural, rich and lifelike (a highlight) vs technically clear but 'dry and sterile' / too forward.

A closer listen.

12 topics · 6 divided
Left: criticalRight: positiveTighter lines: more agreementDashed: limited evidence

Tonality

Leans positiveDivided opinions
Reviewer sentiment11 supporting sources
CriticalNeutralPositive

Band: opinion spread · Dot: weighted average

The most contested question about the set: warm all-rounder or bright, revealing one? In STANDARD mode most hear a studio-neutral, mildly V-shaped balance with sub-bass lift and upper-treble air; the RUMBLE switch adds warmth and slam on demand. Fans call it balanced and versatile; a sizeable camp (including listeners who expected the older Monarchs' warmth) hears it as leaner, brighter and more energetic than they wanted.

Measured

ThieAudio voices STANDARD to a studio-neutral target with a ~10 dB sub-bass shelf cut sharply at 150 Hz and an airy upper treble; the RUMBLE switch adds ~3 dB across the sub-bass shelf (to ~13 dB) plus ~2 dB at 200–500 Hz, making the profile thicker and warmer. On the B&K 5128 (Hawaii Bad Boy's database) it reads as an upward-tilted, sub-bass-boosted set, not a warm/dark one.

Where it splits
A balanced, versatile all-rounder — studio-neutral in STANDARD mode, with the switch adding warmth and slam on demand.55%

“Despite its V-shape, it is both very balanced and very natural.”

Hifitopia, HiFiTopia
Leaner, brighter and more revealing than a 'warm all-rounder' — neutral-bright and energetic in standard mode, not the laid-back set some expect.45%

“flips it from a neutral-bright sounding IEM into one that presents bass first, midrange second.”

Fc-Construct, Headphones.com
Link to this topic

The hardware

Specifications.

Checked

Design

Type
In-ear monitor
Drivers
2 × 8 mm dynamic (IMPACT² isobaric composite-diaphragm subwoofers) + 6 × balanced armature (Sonion) + 2 × electrostatic (Sonion, retuned to 10-40kHz)2DD + 6BA + 2EST
Tuning
Switches · 2 options
Housing
T6 aircraft-grade aluminum alloy shell, CNC-machined

Electrical

Frequency response
10 Hz – 44 kHz

Connection

Cable
Detachable
Connector
2-pin
Plugs supplied
3.5 mm, 4.4 mm balancedmodular

Manufacturer-published figures, not measurements · from thieaudio.com, linsoul.com, headphonezone.in.

Follow the evidence

Sources 13

1–6 of 13 sources

Read with context

Limitations & method.

As of

What to keep in mind 6

  1. This is a read of where opinion sits as of July 2026; the kilobuck IEM space keeps moving, and newer rivals shift the value math.

  2. It shares the Monarch name with the MKIII and the classic MKII, but the drivers, tuning and the new switch make it a different set — check which version a listing or review actually means.

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