In-Ear MonitorOverreview

Moondrop Chu II

The $20 metal IEM everyone hands a beginner — agreed on fit, tuning and value, split on whether its treble is clean or sharp and on how long its brass nozzle survives your ears.

44 sourcesUpdated
$23Typical US price

Score aggregates reviewer opinions across topics.

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Moondrop Chu II

The short version

What to know.

A single-dynamic-driver IEM with a zinc-alloy shell, brass nozzle and detachable cable, now about $23. Reviewers and measurements agree on the tuning: close to the Harman in-ear target through the midrange and presence region, with a few dB of extra bass and an upper-treble lift — a mild V that reads as fun but not extreme, and a clear move toward fuller bass from the original Chu. Most also agree the small shell is comfortable (stock tips aside), detail and imaging are good for the price, and the value is hard to beat, though a minority call it a sidegrade to other $20 sets. The treble is the main sonic split: a slim majority hear it as clean and non-fatiguing, a large minority as bright or sibilant out of the box, and one or two as too restrained; insertion depth, tips and a few weeks of listening all move it. Build splits too: the shell itself is praised, but the brass nozzle tarnishes, moisture builds up behind it, and a steady run of owner reports describe one side going quiet months in — the most-mentioned negative on Amazon. Soundstage divides between 'good for the price' and 'narrow, in-head'; isolation is average.

About this product

The plain 3.5 mm Chu II, released July 2023 at $18.99 and now $22.99 at most stores — a single 10 mm dynamic driver with an aluminium-magnesium alloy composite diaphragm, in a zinc-alloy shell with a screw-off brass nozzle, and a detachable 0.78 mm 2-pin cable (the original 2022 Chu's cable was fixed). Not the USB-C Chu II DSP (in-line mic, app EQ, its own tuning), the original Chu, or the Chu III that followed in August 2026.

Moondrop's Chu II arrived in July 2023, a year after the original Chu had shown that a $20 in-ear could have a metal shell and a carefully measured tuning. The sequel kept the small zinc-alloy body, added the detachable 2-pin cable the first one lacked, gave it a screw-off brass nozzle, and moved the sound from a lean, bright-neutral balance to a fuller one with noticeably more bass.

Three years on it is still one of the most recommended first IEMs, and one of the most measured: more than forty hobbyist rigs hold a graph of it. That long record also holds the arguments — about a top end some hear as clean and others as sibilant, and about nozzles that turn green and earpieces that go quiet once moisture gets in.

A good fit for

  • First-time IEM buyers who want a safe, well-measured mild-V tuning
  • Small ears, side-sleeping and long sessions — the shell is compact and smooth
  • Anyone who wants a metal build and a replaceable cable for about $23
  • Listeners happy to try a few tip sizes to get the seal (and the bass) right

Think twice if

  • You're treble-sensitive and won't tip-roll or EQ — a sizeable share hear it as bright or sibilant at first
  • You live somewhere humid or sweat heavily and won't dry and store them carefully
  • You want a wide, out-of-head soundstage or forward, lush vocals
  • You already own a Wan'er, Zero 2 or Hola — several reviewers call it a sidegrade

The reviewer consensus

Agreement &
disagreement.

3 / 12topics divide opinion
bassmidstonalitydetailimagingcomfortdynamicsisolationvaluetreblebuildsoundstage
9 Mostly agree3 Divided opinions

Common ground7

  • A small zinc-alloy shell with a brass nozzle that feels far above its price, and a detachable 2-pin cable — the fix the original Chu needed.
  • A mild V that measures close to the Harman in-ear target, with a few dB of extra bass and an upper-treble lift.
  • Fuller, better-textured bass than the original Chu, kept out of the midrange — though how much you hear depends on the seal.

Points of contention4

  • Treble: clean and non-fatiguing to a slim majority, bright or sibilant to a large minority, and too restrained to a few — energy above 10 kHz that fit depth, tips and time all change.
  • Build: an overbuilt shell to launch reviewers versus owners reporting green nozzles, moisture behind the filter and one side going quiet months in.
  • Soundstage: decent for the price to some, narrow and in-head to slightly more.

A closer listen.

12 topics · 3 divided
Left: criticalRight: positiveTighter lines: more agreement

Treble

Leans positiveDivided opinions
Reviewer sentiment28 supporting sources
CriticalNeutralPositive

Band: opinion spread · Dot: weighted average

Sources split three ways on the same top end. A slim majority hear it as clean, energetic and non-fatiguing — several Head-Fi reviewers even mention an upper-treble roll-off. A large minority hear it as bright, spicy or sibilant, especially out of the box, and it is the most common sonic complaint among critics and in the Reddit tally. A single reviewer finds it too restrained. Insertion depth and tips move the band in question, and some owners report it softening after a few weeks.

Measured

Across eight squig.link rigs diffed against the Harman IE 2019 target, 6–10 kHz sits between −2.1 and +0.6 dB and 10–16 kHz runs +1.3 to +4.6 dB above it, after a 4–6 kHz dip of −0.7 to −3.4 dB. ASR's GRAS 45CA measurement shows the same thing as 'some overshoot around 14 kHz', which Amir equalised down. SoundGuys' own rig instead reads a 'relative under-emphasis above 5500Hz'. A shallow fit raises 4–6 kHz by about 3 dB over a deep one on sl0the's coupler; tip swaps barely move 6–10 kHz on a coupler, which always seals.

vs. listeners — The graphs show neither a hot presence region nor a big 8 kHz spike — the energy sits mostly above 10 kHz, where rigs and ears disagree most. That is why the same unit draws 'upper treble roll-off' from one listener and 'very sibilant out of the box' from another. Fit depth changes the band that matters, and several owners say it eased over the first weeks ('the treble has ever so slightly become rounder and less piercing'), so there is no single true treble.

Where it splits
Clean, energetic and non-fatiguing — enough sparkle without harshness.53%

“The Chu II also shifts some energy from the upper treble to the mid-treble, which helps provide some of the sparkle that the Chu lacked.”

Bedrock Reviews
Bright, spicy or sibilant — piercing on some tracks, a problem for treble-sensitive ears.42%

“These have spicy treble and instruments can be piercing at times.”

AudioNotions
Too restrained — polite and short on energy, which costs detail.5%

“Its not as dark as the Artti R1 reviewed last week but its still a little restrained for me.”

HiFi Mai Tai
Link to this topic

The hardware

Specifications.

Checked

Design

Type
In-ear monitor
Drivers
1 × 10 mm dynamic (aluminum-magnesium alloy composite diaphragm)
Housing
ZN alloy

Electrical

Impedance
18 Ω
Sensitivity
119 dB/V≈ 101.6 dB/mW
Frequency response
15 Hz – 38 kHz

Connection

Cable
Detachable
Connector
0.78 mm 2-pin
Plugs supplied
3.5 mm

Manufacturer-published figures, not measurements · from moondroplab.com, shenzhenaudio.com.

Follow the evidence

Sources 44

1–6 of 44 sources

Read with context

Limitations & method.

As of

What to keep in mind 6

  1. This is a read of where reviews, owners and measurements land as of October 2026, for a set that has been on sale since 2023 — the $20–25 bracket keeps moving, and the Chu III, Truthear Gate, Tangzu Wan'er and 7Hz Zero 2 are the usual cross-shops.

  2. Fit decides a lot here. The bass depends on getting a full seal (several owners heard almost none until they changed tip size), and how deep the nozzle sits changes the treble — try every tip size before you judge either.

Where to buy Product & retailer links

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