In-Ear MonitorOverreview

THIEAUDIO Monarch MKII

The kilobuck all-rounder that once topped Crinacle's list — near-universal praise for its tuning and midrange, a real split on bass punch, technical ceiling, fit and price.

63 sourcesUpdated
$999Typical US price

Score aggregates reviewer opinions across topics.

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THIEAUDIO Monarch MKII

The short version

What to know.

A $999 tribrid IEM (one 10 mm dynamic driver, six balanced armatures and two electrostatic tweeters per side) that became a default 'neutral kilobuck' recommendation. Across reviewers, forums and owners, the core is broadly agreed: a balanced, reference-leaning tuning with a sub-bass lift; a natural, highly detailed midrange; a mostly well-liked, extended electrostatic treble; clean imaging and layering; handsome, well-made shells (the gripes are the heavy stock cable, a few quality-control reports and the plain case); reasonably good isolation for a vented set; and easy drivability (36 Ω / 108 dB). Measurements back the reference reading: across 32 test rigs it tracks a mainstream target with a full sub-bass shelf, slightly less upper-midrange gain and a 5 kHz presence plateau. Where opinion splits is on bass punch (clean and enough versus lean and blunted), detail (elite versus bettered by cheaper sets), dynamics, fit (the shell is large and a real share of buyers sell it on fit alone) and value. Ear tips, seal and a low-impedance source move its bass more than anything else.

About this product

The second-generation Monarch, launched in late 2021 at $999 — a tribrid with one 10 mm composite-diaphragm dynamic driver, six balanced armatures (two sub-bass, four mid) and two Sonion electrostatic tweeters per side, in a resin shell with a 'lava' foil faceplate. Not the original 2020 Monarch, nor the 2023 MkIII or 2025 MkIV (both 2DD + 6BA + 2EST, with different tuning). It is still sold new alongside the MkIV, and turns up used for roughly half its price.

The THIEAUDIO Monarch MKII is the second-generation Monarch from ThieAudio, the in-house brand of the Chinese retailer Linsoul — a $999 tribrid with one dynamic driver, six balanced armatures and two electrostatic tweeters per side, launched in late 2021. It arrived as the retuned, better-behaved successor to the bass-heavy original Monarch, and Crinacle's IEM ranking list briefly put it at the very top; five years on, it still sits in his top tier with his highest tone grade, and it still sells new beside its MkIII and MkIV successors.

Its reputation rests on tuning: reviewers and owners overwhelmingly call it expertly balanced, with a natural, detailed midrange as its calling card. The arguments are about everything around that — whether the bass is clean and sufficient or lean and short on punch, whether its technical ability is top-tier or merely good for the money, whether the large shell fits, and whether a kilobuck is worth it when cheaper sets get close. Plenty of praise to average, and a real fault line to map.

A good fit for

  • Listeners who want a natural, reference-leaning tuning and a lifelike midrange over bass slam
  • Vocal, acoustic, jazz and classical listeners — the calling-card midrange suits them
  • Treble-sensitive listeners who still want extension — most find the top end smooth
  • Anyone after one safe, do-everything all-rounder at the kilobuck mark
  • Used-market buyers — sets often trade at well under the $999 list price

Think twice if

  • You have small ears or dislike large shells — fit is the most common reason owners sell it
  • You want visceral mid-bass punch and slam — a majority find it lean there
  • You want the last word in technical detail for $1,000 — some hear cheaper sets come close
  • You listen loud to shouty recordings — a minority find the upper mids and 5 kHz region fatiguing
  • You want a warm, thick or 'fun' signature — the MkIII or MkIV lean that way

The reviewer consensus

Agreement &
disagreement.

5 / 12topics divide opinion
tonalitymidstreblesoundstageimagingbuildisolationbassdetaildynamicscomfortvalue
7 Mostly agree5 Divided opinions

Common ground6

  • A balanced, reference-leaning tuning with a sub-bass lift — the reason it became a default kilobuck all-rounder (Crinacle's highest tone grade).
  • A natural, detailed midrange — repeatedly called the set's calling card, and why many prefer it to the MkIII.
  • A mostly smooth, extended electrostatic treble that most listeners find non-fatiguing.

Points of contention5

  • Bass: clean, controlled and sufficient vs lean and short on mid-bass punch — seal and tips move it a lot.
  • Detail: elite midrange resolution vs a technical ceiling that cheaper sets approach.
  • Dynamics: punchy with good contrast vs muted and a little sterile.

A closer listen.

12 topics · 5 divided
Left: criticalRight: positiveTighter lines: more agreement

Tonality

PositiveMostly agree
Reviewer sentiment28 supporting sources
CriticalNeutralPositive

Band: opinion spread · Dot: weighted average

The strongest point of agreement: a balanced, reference-leaning tuning with a sub-bass lift that nearly every reviewer and most owners call expertly done — 'one of the best tunings' for Chrono, 'impeccably balanced' for Fc-Construct. The dissent is about character, not correctness: a minority find it lean, dry or clinical, and even fans concede it can read as 'too normal.'

“The MKII possesses one of the best tunings I’ve heard on an IEM, and I like this tonality even more than that of the V16 Divinity.”

Chrono, headphones.com

“The MkII has an impeccably balanced profile”

Fc-Construct, headphones.com

“I find that it leads this to being just a sound that's a little bit too lean, a little too dry.”

Super* Review (video)

Measured

Across 32 squig.link rigs (normalised at 500 Hz, against the Harman IE 2019 target) the sub-bass shelf sits at target level (−0.6 dB median at 20–60 Hz), the 100–200 Hz region on target, the ear-gain peak ~2.8 kHz about 3 dB under target, with a 5 kHz plateau and a 6–7 kHz notch. Crinacle labels it 'Neutral with bass boost' with an S+ tone grade.

Link to this topic

The hardware

Specifications.

Checked

Design

Type
In-ear monitor
Drivers
1 × 10 mm dynamic (composite diaphragm) + 6 × balanced armature + 2 × electrostatic (Sonion)1DD + 6BA + 2EST

Electrical

Impedance
36 Ω
Sensitivity
108 dB/mW≈ 122.4 dB/V

Connection

Cable
Detachable, 1.2 m
Connector
0.78 mm 2-pin (not recessed)community-sourced: socket depth
Plugs supplied
2.5 mm balanced, 3.5 mm, 4.4 mm balancedmodular

Manufacturer-published figures, not measurements · from linsoul.com, thieaudio.com. Socket depth not published by the maker — community-sourced from hands-on reviews: headphones.com, audiophileon.com.

Follow the evidence

Sources 63

1–6 of 63 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 September 2026. The MKII is still sold new at $999, but it has two successors (MkIII and MkIV) and turns up used for much less, so the price picture keeps moving.

  2. It shares the Monarch name with the original 2020 Monarch, the MkIII and the MkIV — different drivers and tuning — so check exactly which version a listing or review means.

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