In-Ear MonitorOverreview

TANCHJIM Fission

Twelve tunings, one voice — and a bass dial that only ever takes bass away.

17 sourcesUpdated
$130Typical US price

Score aggregates reviewer opinions across topics.

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TANCHJIM Fission

The short version

What to know.

A $130 single-dynamic-driver IEM built on the same DMT5 driver as Tanchjim's pricier Origin, sold on adjustability: three screw-in nozzles, a four-position bass dial and a USB-C plug that adds app-driven DSP and parametric EQ. Sources agree on the essentials — forward, natural vocals, a safe treble with no sibilance, stable imaging, average isolation, and a metal-and-modular-cable package that reads above its price. They split on nearly everything else: whether the deliberately modest bass is correct or simply too light, whether resolution is class-leading or mid-pack, whether the stage is unusually open or plainly intimate, and whether $130 is a bargain or matched by cheaper rivals. Measurements settle one thing the marketing does not: every dial position other than the stock Atmosphere setting only removes sub-bass.

About this product

Tanchjim's $130 single-DD, not the pricier Origin it borrows the DMT5 driver from, and not the $20 Bunny. Later offered in a black co-branded edition alongside the original champagne finish.

Tanchjim built the Fission around a simple pitch: take the DMT5 driver from the $260 Origin, put it in a lighter aluminium shell, and hand the listener the tuning controls. Three screw-in nozzles, a four-position bass dial you turn with the included screwdriver, and a modular cable whose USB-C plug turns into a DSP module with app presets and parametric EQ — twelve advertised sound profiles, and rather more than that once the app is involved.

What arrived is less a chameleon than people expected. Reviewers converge quickly on what the Fission sounds like — vocal-forward, safely tuned, light on bass — and then diverge on almost every judgement that follows from it. The measurements are unusually helpful here, because several of the arguments turn out to be two descriptions of one curve.

A good fit for

  • Vocal-first listening — rock, indie, acoustic, classical and singer-songwriter material.
  • Anyone who wants a safe, non-fatiguing tuning they can wear for a full working day.
  • Tinkerers: between the dial, the nozzles and the app PEQ, few sets at this price are as adjustable.
  • Gaming and dense mixes, where stable imaging matters more than bass slam.
  • Listeners drawn to the pricier Tanchjim Origin who want most of that voicing for less.
  • Phone-only listeners — the USB-C plug means no separate dongle.

Think twice if

  • You want sub-bass rumble and slam for EDM, hip-hop or rap — the shelf is modest by design and no setting adds to it.
  • You are chasing maximum resolution at $130; several reviewers put it mid-pack there.
  • You want a big, out-of-head stage.
  • You would rather have one clearly right tuning than a dial, three nozzles and an app to work through.
  • Your ears are fussy about seal — the shallow lip makes tip choice matter more than usual.
  • You are on iOS: the DSP app is Android and Windows only, so the USB-C plug loses its best trick.

The reviewer consensus

Agreement &
disagreement.

6 / 12topics divide opinion
imagingisolationbuildmidstrebletonalitybasssoundstagedetaildynamicscomfortvalue
3 Strong agreement3 Mostly agree6 Divided opinions

Common ground9

  • Vocals are the strong suit — forward, clear and natural, and they rarely turn shouty.
  • The treble plays it safe: extended and clean, with no sibilance or hot peaks for most listeners.
  • Imaging is a real strength for the money, helped by channel matching inside 0.6 dB.

Points of contention9

  • Bass: deliberately clean and well-judged, or simply too light? It extends flat to 20 Hz but sits about 4 dB under a Harman-style shelf.
  • Resolution: class-leading for the price, or the Fission's weak spot? Reviewers split almost evenly.
  • Soundstage: unusually open for one dynamic driver, or plainly intimate and class-typical.

A closer listen.

12 topics · 6 divided
Left: criticalRight: positiveTighter lines: more agreement

Bass

Leans criticalDivided opinions
Reviewer sentiment12 supporting sources
CriticalNeutralPositive

Band: opinion spread · Dot: weighted average

Sources split hard. Everyone describes the same thing — deep but modest, mid-bass-led — and then disagrees about whether that is a well-judged neutral low end or the set's main limitation. The split tracks genre: acoustic and vocal listeners are content, EDM and hip-hop listeners are not.

Measured

Stock (silver nozzle, Atmosphere), the bass shelf measures about +5.6 dB at 50 Hz relative to 500 Hz and holds within a decibel all the way down to 20 Hz — genuinely flat extension, but roughly 4 dB less shelf than a Harman-style in-ear target. The dial spans 21.7 dB at 20 Hz across its four positions and only 3.9 dB at 200 Hz: it is a sub-bass high-pass, and the stock position is already the maximum.

vs. listeners — Both camps are reading the same curve. The sub-bass really is there — the trace is flat to 20 Hz — but there is simply less of it than a Harman-tuned rival, so 'well-extended' and 'not enough rumble' are both accurate; they weight extension against quantity differently. What no camp disputes is the direction of the dial: it subtracts.

Where it splits
too light — extension without rumble, and no setting adds any59%

“Bass is more focused in the midbass than sub bass, so it lacks a little sub bass extension and is noticeable when playing music like electronica or some hip hop.”

Leonarfd, Head-Fi
clean, punchy and correctly judged for a neutral set41%

“The bass response is clean, controlled, and well-extended, with the DMT5 driver delivering impressive sub-bass extension and punchy, articulate mid-bass.”

Pragmatic Audio
Link to this topic

The hardware

Specifications.

Checked

Design

Type
In-ear monitor
Drivers
1 × dynamic (5th-gen DMT5, inner and outer double-magnetic circuit, double-chamber)

Electrical

Impedance
16 Ω
Sensitivity
126 dB/V≈ 108 dB/mW
Frequency response
8 Hz – 48 kHz

Connection

Cable
Detachable
Connector
0.78 mm 2-pin
Plugs supplied
3.5 mm, 4.4 mm balanced, USB-C (DAC in plug)modular

Manufacturer-published figures, not measurements · from tanchjim.com, hifigo.com.

Follow the evidence

Sources 17

1–6 of 17 sources

Read with context

Limitations & method.

As of

What to keep in mind 6

  1. This is a read of where the reviews land as of July 2026. The sub-$150 single-DD bracket turns over fast, and the Fission gets cross-shopped constantly against the Simgot EW300, Truthear Pure, Kiwi Ears KE4 and Tanchjim's own Origin, Nora and Bunny.

  2. Owner star ratings come mostly from people who chose to buy the thing, so they skew positive — and the 4.3 average here rests on 19 ratings, which is a small sample. Weigh the written impressions more heavily than the number.

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