In-Ear MonitorOverreview

Letshuoer S12 Ultra

The S12 with the treble filed down: the smoothest, most comfortable, best-boxed version of a budget-planar legend — and the one that finally splits its fans on whether it lost the plot.

63 sourcesUpdated
$169Typical US price

Score aggregates reviewer opinions across topics.

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Letshuoer S12 Ultra

The short version

What to know.

A $169 single-planar IEM tuned warm of the S12 formula: a sub-bass-first shelf about 12 dB over the lower mids, an ear-gain peak that arrives early and sits 5–6 dB under the Harman curve through 3–4 kHz, and a 5–8 kHz plateau with the 8 kHz peak trimmed but not removed. Reviewers broadly agree on tight, fast, textured bass that reaches deep without bloom; a treble that is smooth, sibilance-free and non-fatiguing where earlier S12s were sharp; class-leading comfort from a small, light metal shell; a bulletproof build with one of the best stock cables under $200; and strong value — the ranking sites, the community and most critics call it the S12 to buy. The fault lines are the midrange (organic and full to most, recessed, thin or emotionally flat to a vocal minority), the treble (smooth and right to most, too polite for planar fans or still hot and grainy to the treble-sensitive), the soundstage (wide and layered versus intimate and in-the-head, an even split), and how much power it wants — it plays loud from the bundled dongle, and several reviewers hear it tighten and open up with a stronger source. Versus its siblings the graphs are unambiguous: it is the S12 2024 to within a decibel below 6 kHz, and about 2.5 dB quieter at 8 kHz than the S12 Pro.

About this product

The fourth and, per Letshuoer, final S12 (2025): the same 14.8 mm planar driver and CNC-aluminium shell as the S12, S12 Pro and S12 2024 Limited Edition, retuned warmer and smoother, with a 392-core silver-plated-copper cable whose plug screws between 3.5 and 4.4 mm and a bundled DT01 Pro USB-C dongle. In Gunmetal Gray or Mocha. It measures within a decibel of the S12 2024 below 6 kHz on every shared rig; it is not the brighter S12 Pro (covered separately), the smaller S08 or the newer Astralis.

Letshuoer's S12 has been the default answer to 'best planar under $200' since 2021, through the S12 Pro and the gold S12 2024 Limited Edition, and its bright, fast, slightly aggressive top end was always the argument. The S12 Ultra, launched in autumn 2025 at $169 as the series finale, keeps the same 14.8 mm planar and the same small aluminium shell but pulls that treble in, adds a touch more sub-bass, and packs the box with a screw-locked modular cable, two tip families and a USB-C dongle.

Twelve months on, almost everyone agrees it is the easiest S12 to live with: comfortable, superbly built, tight and deep in the bass, with no sibilance and no planar zing. The argument is about what the softening cost. One camp hears the most natural, organic midrange a cheap planar has managed; another hears vocals pushed back into a scoop with nothing to anchor them — and the graphs show why both can be right.

A good fit for

  • Listeners who wanted the S12's speed and bass but were put off by its treble
  • Long, relaxed sessions — vocal, rock and jazz libraries that suit a warm-neutral tilt
  • Small ears and all-day wear: the shell is among the easiest planar fits going
  • A first planar with everything in the box — modular cable, tips and a dongle — for $169

Think twice if

  • You want forward, intimate vocals — the upper mids sit a step back by design
  • You are a treble-head or a detail-first listener: the S12 2024, S12 Pro and Timeless II resolve and sparkle more
  • You want a big, tall, holographic stage rather than a wide-but-close one
  • You already own an S12 2024: the graphs and most ears say the two are near-identical

The reviewer consensus

Agreement &
disagreement.

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

Common ground6

  • Deep, fast, textured sub-bass that reaches lower than the S12 Pro and never bleeds into the mids
  • The sharpness and sibilance of earlier S12s are gone — it is the least fatiguing S12 by a distance
  • A small, light, flush-fitting aluminium shell that ranks among the most comfortable planars

Points of contention5

  • Midrange: the most natural, organic vocals a budget planar has managed, or a scoop that leaves vocals thin, distant and emotionally flat
  • Treble: smooth and finally right, too polite for anyone who liked planar sparkle, or still hot and grainy for the treble-sensitive
  • Soundstage: wide and layered with real depth, or intimate and in-the-head with height and depth cut back from the S12 2024

A closer listen.

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

Bass

PositiveMostly agree
Reviewer sentiment57 supporting sources
CriticalNeutralPositive

Band: opinion spread · Dot: weighted average

The most consistently praised region: deep, fast, textured and controlled, a sub-bass-first shelf that reaches lower than the S12 Pro without bleeding into the mids. The caveats are about quantity and character rather than quality — mid-bass slam is lighter than a dynamic driver's, a few hear it as slightly boomy on dense mixes, and a small minority (mostly on weaker seals or sources) hear it as lean.

“The bass is stunning. It’s powerful but not overpowering; it’s detailed and textured.”

Chris, The Headphoneer

“In real music, the result is a very compact bass, with quite a punch, dry, tight, very fast and with hardly any decay.”

cqtek, HiEndPortable

“I think all of these have a little bit too much bass for my personal taste, but it's fun.”

Super* Review (video transcript)

“I think the number one issue that some folks will have with the S12 Ultra is that the mid-bass doesn’t have that forward and profuse slam that some may like.”

Chris Love, Mobileaudiophile

“Excellent IEMs for its price. Clear mids and highs. Bass are on the weaker side.”

Amazon customer (in the listing's review highlights)

Measured

Twelve-rig average, 500 Hz-normalised: +11.8 dB at 20 Hz (sd 0.9), +10.4 at 40 Hz, +8.7 at 60 Hz, +6.0 at 100 Hz, +2.4 at 200 Hz — 2.8 dB above Harman IE 2019 at 20 Hz and 1.5–1.9 dB above it from 60 to 250 Hz. Versus the S12 Pro on seven shared rigs it has +2.2 dB at 20 Hz and about 1 dB less from 100 to 250 Hz: more sub-bass, slightly less mid-bass.

vs. listeners — The shelf is sub-bass-first on every rig, yet a few listeners describe punch without rumble or a lean bottom end; with a bass region this consistent across rigs, a shallow seat or leaky seal is the likelier explanation than unit variation.

Link to this topic

The hardware

Specifications.

Checked

Design

Type
In-ear monitor
Drivers
1 × 14.8 mm planar magnetic
Housing
aluminum alloy

Electrical

Impedance
16 Ω
Frequency response
20 Hz – 40 kHz

Connection

Cable
Detachable, 1.2 m
Plugs supplied
3.5 mm, 4.4 mm balancedmodular

Manufacturer-published figures, not measurements · from letshuoer.net, linsoul.com.

Follow the evidence

Sources 63

1–6 of 63 sources

Read with context

Limitations & method.

As of

What to keep in mind 8

  1. A read of where the reviews land as of mid-September 2026, a year after launch. The written and video verdicts cluster in October and November 2025; the owner reviews run through the summer of 2026 and are, if anything, a little more mixed than the launch-month critics were.

  2. The owner ratings skew positive because they come from people who chose to buy a warm planar: Amazon's 4.4 is from 83 ratings pooled across both colours, Letshuoer's own store shows 4.96 from 23, and Head-Fi's 27 reviews average 4.3 — twenty of those were loaners or review units from the maker or its review tours.

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