Audiowords
TANCHJIM Fission

TANCHJIM Fission

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

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.

OverreviewIn-Ear Monitor17 sourcesas of 2026-07-27

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.

The overview

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.

Where they agree

  • 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.
  • The package punches above $130 — light all-metal shells and an unusually good modular cable with 3.5 mm, 4.4 mm and USB-C DSP plugs.
  • The bass dial only ever removes bass; the stock Atmosphere position is where nearly everyone ends up.
  • The three nozzles change the sound, but only slightly — about a decibel, not a new tuning.
  • Isolation is average, as it is for most vented dynamic drivers; tips and seal do the work.
  • It is easy to drive and does not need a dedicated amp.
  • You get a cloth pouch, not a case — the one accessory complaint everyone shares.

Where they split

  • 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.
  • Dynamics: punchy and well textured, versus pillowy and short on slam.
  • Character: most hear neutral with a hint of warmth, but one detailed review calls it cold and dry and another hears it as bright and V-shaped with recessed vocals.
  • Fit: comfortable for hours for most, fussy and seal-dependent for a minority, thanks to a shallow shell lip.
  • Value: a bargain against the Origin, or undercut by cheaper rivals like the Simgot EW300.
  • Which nozzle-and-dial combination is actually best — recommendations run from stock silver at Atmosphere to brass with the dial moved.
  • The USB-C DSP: a second IEM in the box, or a convenience that gives up resolution?
The verdict, mappedEvery aspect on one axis — criticized to praised. Hover a point for its spread; click to jump.
CriticizedNeutralPraised

By aspect — in detail

Bass

Contested · 12 src

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

Mids

Moderate · 10 src

The most consistent praise in the set. Vocals sit forward, read natural, and almost never turn shouty; male and female voices are usually said to fare equally well. One review dissents sharply, hearing the voices as recessed.

“The midrange shines with excellent vocal clarity and natural timbre”

Pragmatic Audio

“Midrange is smooth and soft, it is very addictive and beautiful sounding on both vocals and instruments.”

Leonarfd, Head-Fi

“Vocals sit forward enough to stay engaging without ever sounding shouty or recessed.”

AudioNaut18, Head-Fi

“This mid range offers some of the best transparency with very good clarity.”

Suman Sourav Meher, The Headphone List
Measured

Ear gain peaks at +8.6 dB around 3.45 kHz relative to 500 Hz — present, but a couple of decibels under a Harman-style in-ear target, which is the usual recipe for vocals that are forward without being shouty.

⚠ vs. listeners — One outlier hears the opposite: Audiophile Heaven reports 'a dip right in the middle, which sucks out the voices a bit'. The measured curve shows no such dip, and no other source hears one, so it is recorded here as a minority read rather than folded into the average.

Treble

Moderate · 11 src

Broad agreement that it is safe: extended and clean, without sibilance or hot peaks, and comfortable for long sessions. The dissent is about air — some find it well extended, others find the top end closes in — and one review hears it as outright bright.

“Highs is also very well elevated, Fission is definitely one of the better single DDs for clean and well extended treble.”

Leonarfd, Head-Fi

“the treble provides good extension and detail without harshness”

Pragmatic Audio

“The treble is smooth and well extended with no distracting peaks.”

AudioNaut18, Head-Fi

“it definitely gets slightly darker in the upper treble region”

Suman Sourav Meher, The Headphone List

“Can be rather sharp and will reveal harshness and grain really easily”

Audiophile Heaven
Measured

Upper treble rolls off in the stock fit: -2.6 dB at 10 kHz and -4.8 dB at 16 kHz relative to 500 Hz. Below 8 kHz all eight measured nozzle-and-dial configurations sit within about 1.5 dB of one another; above 8 kHz, insertion depth alone swings the response by more than 10 dB (a shallow fit puts +8.7 dB at 12 kHz, a deep one +9.1 dB at 10 kHz).

⚠ vs. listeners — The rig explains why one treble gets so many different descriptions. Everything below 8 kHz is stable no matter which nozzle or dial position you choose, but how deep the Fission sits in your ear moves the 8–12 kHz region more than any of the tuning controls do. The 'safe and smooth' majority and the lone report of a bright 12 kHz peak may simply be seating them differently.

Tonality

Moderate · 11 src

The majority reading is neutral with a touch of warmth and a vocal-forward tilt. The level of approval is consistent; the label is not — one detailed review calls it cold and dry, another hears it as bright and V-shaped, which is why this stops short of a firm consensus.

“a slightly warm-neutral signature with excellent technical performance across all frequencies”

Pragmatic Audio

“It barely had any warmth as it leans towards a more neutral tonality.”

Suman Sourav Meher, The Headphone List

“TanchJim Fission sounds fairly bright, Deep, V-Shaped, crisp and fun.”

Audiophile Heaven

“Bass is too relaxed with a slightly congested low midrange, average detail and soundstage, and there are stronger alternatives at a similar price.”

Audio-In Reviews, via IEMRanking
Measured

The stock trace is close to textbook neutral: a ~+5.6 dB bass shelf, -0.4 dB at 1 kHz and a +8.6 dB ear-gain peak at 3.45 kHz, all relative to 500 Hz. Nothing in it supports a V-shape, and nothing suggests a bright tilt below 8 kHz.

Soundstage

Contested · 9 src

Cleanly split into two clusters with nothing in between: one group is surprised by how open it sounds for a single dynamic driver, the other calls it plainly intimate and normal for the class. Depth is the more common complaint of the two.

Where it splits
intimate — close-in and class-typical51%

“Soundstage is a little intimate, not in a bad way just that the stage is not very wide and deep.”

Leonarfd, Head-Fi
unusually open for one dynamic driver49%

“The soundstage is surprisingly spacious for a single dynamic driver IEM, with good width and depth”

Pragmatic Audio

Imaging

Strong consensus · 7 src

The clearest technical strength. Instrument placement is consistently called precise and stable, and it is the reason the set keeps getting recommended for gaming and dense mixes even by reviewers who are lukewarm elsewhere.

“Imaging is a relative strength for the price, making positional cues feel clear and stable”

IEMRanking (9-review aggregate)

“Instrument placement though is very good.”

Suman Sourav Meher, The Headphone List

“The layering and separation remain excellent regardless of tuning choice, maintaining clarity even in busy passages.”

Pragmatic Audio
Measured

Left and right channels track each other to within 0.58 dB across the whole 20 Hz–8 kHz span on an independent rig — unusually tight matching at this price, and the physical basis for a stable centre image.

Detail

Contested · 11 src

The most evenly split aspect in the set. One half calls the resolution class-leading for $130; the other calls it the Fission's weak spot and puts it mid-pack for the bracket. Both halves include careful, comparison-driven reviewers.

Where it splits
class-leading resolution and clarity for the money52%

“Tuned to deliver class leading resolution and definition this IEM can sound slightly cold and dry at times.”

Suman Sourav Meher, The Headphone List
modest — resolution is the weak spot, average for the bracket48%

“even if Fission is decently technical it cannot pick up as much details in the music as DX1”

Leonarfd, Head-Fi

Dynamics

Contested · 7 src

Sources split on slam. Most hear enough punch and good texture; a substantial minority — including the harshest critic in the set — hear the bass attack as pillowy and the presentation as short of bite.

Where it splits
punchy and well textured60%

“it has lots of texture and dynamic range is quite large”

Leonarfd, Head-Fi
pillowy — short on slam and bite40%

“the bass attack reads a touch pillowy and the whole presentation stops short of truly incisive”

Super* Review, via IEMRanking

Comfort

Contested · 9 src

Most reviewers find the small, light metal shells comfortable for hours, several explicitly calling out the CIEM-like contour. A real minority reports the opposite problem: a shallow lip that makes the seal fussy and depends heavily on tips.

Measured

Fit matters more here than the tuning controls do: shallow versus deep insertion moves the 8–12 kHz region by over 10 dB on the same rig, while a nozzle swap moves the response about 1–1.5 dB. Pragmatic Audio also flags the 6.4 mm nozzle diameter as potentially large for smaller canals.

Where it splits
small, light and comfortable for long sessions83%

“The Fission features a compact shell design that fits comfortably in most ear shapes”

Pragmatic Audio
fit is picky — shallow lip, seal depends on tips and ear shape17%

“the fit can be a challenge for some as the shell lacks a pronounced lip, and the nozzles can be tricky to remove and replace”

Jaytiss, via IEMRanking

Isolation

Strong consensus · 3 src

Consistently described as average — normal for a vented dynamic driver. No source rates it a strength or a failing; how much you get comes down to tips and seal.

“Isolation is decent but not exceptional, which is typical for vented dynamic driver IEMs”

Pragmatic Audio

“Medium passive noise isolation”

Audiophile Heaven

“the shell/nozzle design is often described as having a less pronounced lip, so seal depends heavily on tips and ear shape”

IEMRanking (9-review aggregate)

Build

Strong consensus · 9 src

Broad agreement that the package overdelivers: light all-metal shells, a glass faceplate, and a modular cable that several reviewers single out as the best they have seen under $150. The one shared complaint is the accessories — a cloth pouch instead of a hard case.

“The build quality of the Fission is excellent, featuring full metal shells with a matte finish that prevents fingerprints and scratches”

Pragmatic Audio

“this is definitely one of the most beautiful looking cables with an IEM priced under $150”

Suman Sourav Meher, The Headphone List

“the build quality on everything from the IEMs themselves to the accessories is exceptional”

Z-Reviews, via IEMRanking

“Accessory bundle and carry solution feel undercooked for the price, and the nozzle changes are subtle if stronger treble shaping is expected.”

Audio Amigo, via IEMRanking

Value

Contested · 12 src

Genuinely divided, and the division is about rivals rather than the Fission itself. One side sees flagship-adjacent tuning plus a DSP cable for $130; the other points out that cheaper sets deliver similar technical ability with more bass. Scores across nine expert reviews cluster in the sixes.

Measured

The aggregate reflects the split rather than resolving it: nine expert reviews average 6.8/10, and the aggregator notes the spread itself — ratings are moderately scattered, roughly 6.0 to 7.3 out of 10 across several reviewers.

Where it splits
outstanding — most of the Origin, plus a DSP cable, for half the money52%

“Considering the significant price difference, the Fission represents remarkable value”

Pragmatic Audio
a tougher sell — cheaper rivals match it on sound48%

“The EW300, in particular, offers more bass, tuning variety, and similar technicalities for half the price, making the Fission a tougher sell”

Jays Audio, via IEMRanking

Best 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.

Skip 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.

At a glance

↳Consensus
76 / 100weighted mean across 17 sources — an aggregate, not a single verdict
↳Type
IEM
↳Sources
17 · 6 classes
↳As of
2026-07-27
↳Owner rating
4.3/5 · 19small, self-selected sample — skews high

Where to buy

Sources17 reviews across 6 classes. Weight reflects expertise × independence; echoes collapsed.
  1. s1Tanchjim Fission IEM — measured review of all tuning modes (FR, channel matching, distortion)Pragmatic AudioEditorial2025-07-23w0.95
  2. s2Tanchjim Fission — raw frequency-response exports, 8 configurations (nozzles, dial positions, insertion depth, L/R)Super* Review squig.link databaseMeasurement2025w1.00
  3. s3Tanchjim Fission Review: Prioritizing Mid Range Details and ClaritySuman Sourav Meher, The Headphone ListEditorialunknown2025-07-06w0.80
  4. s4TANCHJIM Fission — Oxygen for cheap (3/5; volume-matched comparison against the Letshuoer DX1)Leonarfd, Head-FiCritical2025-06-08w0.90
  5. s5TANCHJIM Fission Review – A Mid-Centric Detail Monster with a Gentle Touch (3.5/5)MD Rohit, Head-FiCriticalaffiliate2025-07-05w0.70
  6. s6Tanchjim Fission Review - The All Rounder (5/5)AudioNaut18, Head-FiOwnerunknown2025-10-20w0.60
  7. s7Fifth Generation Dynamic Driver Sound – TanchJim Fission IEMsAudiophile HeavenEditorialaffiliate2025-08-12w0.60
  8. s8TANCHJIM Fission — r/iems comment aggregation (70% positive across 20 impressions)RedditRecsCommunityaffiliate2026-07-27w0.70
  9. s9Tanchjim Fission — 9-review score aggregate (6.8/10, B tier)IEMRankingEditorialaffiliate2026w0.50
  10. s10Tanchjim Fission — critical video verdict (6/10; pillowy bass attack, novelty dial)Super* Review, via IEMRankingCritical2025-09-05w0.85
  11. s11Tanchjim Fission — video review (6.6/10; open stage, modest resolution, prefer the DSP connector)Paul Wasabii, via IEMRankingVideo2025w0.65
  12. s12Tanchjim Fission — video review (6.5/10; cheaper Origin, but the EW300 undercuts it)Jays Audio, via IEMRankingVideo2025w0.60
  13. s13Tanchjim Fission — video review (6.3/10; neutral and versatile, but relaxed bass and average technicalities)Audio-In Reviews, via IEMRankingVideo2025w0.60
  14. s14Tanchjim Fission — video review (6.8/10; warm controlled bass, undercooked accessories)Audio Amigo, via IEMRankingVideo2025w0.60
  15. s15Tanchjim Fission — video review (6.3/10; near-Origin sound, but a fit that fights some ears)Jaytiss, via IEMRankingVideo2025w0.55
  16. s16Tanchjim Fission — video review (7/10; brass nozzle plus Pop mode, flagship-tier package)Z-Reviews, via IEMRankingVideo2025w0.55
  17. s17TANCHJIM Fission — Head-Fi owner star aggregate (19 ratings averaging 4.3/5, range 3.0–5.0)Head-Fi showcaseOwnerunknown2026w0.55

Limitations & method

Consensus-of-sources synthesis · as of 2026-07-27 · not a measurement verdict or ground truth.