Design and model identity
6063 CNC aluminium shell; dual-magnet, dual-cavity design.
Fosi Audio IM4
Click your selection again to undo.
Product information
At a glance
Emphasis: Bass emphasisTimbre: Warm toneListening: Relaxed listening
A candidate for listeners seeking bass weight and impact, warmth and body and calm, extended listening.
Technical / Musical 82 / 86Retained editorial scores16 Source recordsSignature evidence · HighPrice record date · 2026-10-10Evidence for the catalogue referenceListing price: USD 99.99 · 2026-10-25
Scores are retained editorial reference values, not laboratory measurements or arithmetic averages of review stars. A one-point difference does not establish absolute superiority. Signature confidence is separate from score certainty.
Read the scores and evidence ↗Core product facts
- Release month
- 2025-09
- Driver configuration
- 1DD (10mm Be-coated)
- Impedance
- 21Ω
- Earpiece connector
- 0.78mm 2-pin
- Catalogue reference · KRW
- ₩137,898USD 99.00
- Emphasis · timbre
- Emphasis: Bass emphasis · Timbre: Warm tone
A recorded reference amount, not a live lowest price.
Basic specifications
Specifications retained from product records; missing values are not estimated. Korean source wording is preserved where no verified translation exists.
| Driver configuration | 1DD (10mm Be-coated) |
|---|---|
| Impedance | 21Ω |
| Sensitivity | 109 dB stated; reference unspecified |
| Weight and scope | Officially 7 ±0.5 g per side and about 38 ±1 g including the cable. Earpiece and total weights are distinct.Specification source ↗ · fosiaudio.com |
| Nozzle diameter | No established value in the checked records. Value not established · checked source ↗ · fosiaudio.com |
| Included accessories |
|
| Cable conductor / material | 5N OFC silver-plated copperSpecification source ↗ · cdn.assets.prezly.com |
| Cable cores / braid | 4 cores · 392 wires totalSpecification source ↗ · cdn.assets.prezly.com |
| Cable length | No established value in the checked records. Value not established · checked source ↗ · fosiaudio.com |
| Earpiece connector | 0.78mm 2-pin |
| Source plug | 3.5 mm gold-plated · separate 4.4 mm cable not includedSpecification source ↗ · cdn.assets.prezly.com |
Retained product source ↗ · fosiaudio.com · Specification evidence · Research coverage
Package/cable records below retain the original source language. Purchase options, modular plugs and aftermarket accessories are distinguished; unverified counts and materials are not estimated.
공식본문 기본구성목록은3.5mm 케이블. 별도4.4mm 옵션을 동봉품으로 합산하지 않음.
Fosi Audio IM4 기존 제품 자료 ↗ · fosiaudio.comFosi Audio IM4 official package list ↗ · fosiaudio.comPrice and release evidence
These amounts use different bases. The KRW reference is used for catalogue sorting and filters; the listing quote uses the stated currency and option. Do not treat them as comparable current KRW checkout prices.
Listing price
USD 99.99
Checked: 2026-10-25 · Page-reported status: Reported in stock
Open listing ↗ · fosiaudio.comPublicly posted amount only. Options, region, shipping, tax, coupons and final checkout require separate verification. This does not validate the historical KRW reference or update its exchange rate.
Catalogue reference · KRW
Historical source for the KRW reference not secured
₩137,898
Retained USD reference. The current regular AliExpress price for the same option has not been verified.
Reference conversion: US$99 × ₩1392.91/USD → ₩137,898 · 2025-09 monthly rate
The original product-price URL was not retained for this reference amount. A general product page or an exchange-rate page is not proof of that exact selling price.
Exchange-rate data only ↗ · fred.stlouisfed.org
Pricing record date: 2026-10-10
This is the registered reference price, not a live lowest-price quote. Option, shipping, tax, coupons and exchange-rate rounding may differ.
Driver and design evidence
1DD (10mm Be-coated)
Recorded model / design notes (original language): 6063 CNC 알루미늄 합금 셸, N52 듀얼 마그넷·듀얼 캐비티 구조입니다.
Product specifications / model-specific reference ↗ · fosiaudio.com
Additional product reference: Prime Audio · IM4 · primeaudio.org
Additional product reference: Pragmatic Audio — Fosi Audio IM4 · pragmaticaudio.com
Linked references are the existing model-specific specification/design records. Manufacturer, retailer and review sources are distinguished in the original pages. Driver counts alone do not establish sound quality; model generations and variants must match.
6063 CNC aluminium shell; dual-magnet, dual-cavity design.
A 10mm beryllium-coated DD with vented acoustics and two nozzle materials. Frequency emphasis and timbre are listed separately.
Representative character: Relaxed listening
2ann quick note
Author sign-inLoading note…
Sound, assessment & measurements
Technical evaluation 82 / 100
Bass88
Mids81
Treble80
Spatial presentation85
Evidence behind the technical assessment
Treble presentation: Black is gentler; brass can add sparkle and sharpness. ↗
Stage and separation: Open lateral space, with limits in complex layering. ↗
Read sources and disagreements ↗Musical enjoyment 86 / 100
Natural timbre84
Emotional expression85
Immersion88
Rhythm and dynamics90
Vocal and instrumental liveliness85
Long-session comfort84
Evidence behind musical enjoyment
Bass character: Thick, warm mid-bass; control varies with tips and nozzles. ↗
Vocals and mids: Natural to slightly recessed vocals with useful body. ↗
Read sources and disagreements ↗Sound and listening impressions
Design, bass, mids, treble, stage and differing reviewer impressions are presented together.
Sound classification
Representative listening character
Smooth flow and full, warm texture favour relaxed listening. It does not promise fatigue-free sound in every setup. This editorial browsing category is drawn from retained model-specific reviews; it does not exclude other listening uses.
Similar listening character ↗Frequency emphasis: Bass emphasis. Thick, warm mid-bass; control varies with tips and nozzles. Overall timbre: Warm tone. These are separate representative axes; fit, nozzle settings and contrary accounts remain in the reviewed evidence.
Differences by listening conditions: Brass nozzles and tips alter brightness and vocal position. Brighter analytical reports and bass-overload impressions remain valid dissent.
Concise English summaries distinguish product specifications, reviewed listening impressions and practical advice. Original source notes remain available below.
Bass quantity and texture
Thick, warm mid-bass; control varies with tips and nozzles.
Vocal placement and midrange
Natural to slightly recessed vocals with useful body.
Treble and fatigue
Black is gentler; brass can add sparkle and sharpness.
Stage, separation and imaging
Open lateral space, with limits in complex layering.
Disagreement and listening conditions
The bass, vocal and treble descriptions summarise reviewed impressions, not measured quality. Tips, volume, nozzle settings and source conditions can explain differences. Sample relationships and duplicate authors remain disclosed in the source records.
Strengths and caveats from reviewed sources
Supplementary notes retain the original Korean research wording.
Prime Audio · IM4 ↗ — 검정 노즐 기준 따뜻한 약한 V형, 중저음 강조와 부드러운 고음.
Pragmatic Audio — Fosi Audio IM4 ↗ — 따뜻한 저역과 약간 물러난 중역, 선명하되 비교적 안전한 고역의 재미있는 V형. 기본 알루미늄 노즐보다 황동 노즐이 밝아진다. 넓고 깊이 있는 무대는 장점, 엄밀한 음색 정확도와 최고 수준의 기술성은 제한적이라고 평가한다.
Listening suggestions and selection points
Start with calm pop, acoustic or vocal music and focus on continuity and flow. Balance the appeal of smoothness against whether you want more sparkle or stronger impact.
These are editorial starting points derived from the existing sound descriptions, not results of a genre-by-genre test. Recordings and arrangements vary even within one genre.
How to choose this product
Preferences that match
- bass weight and impact · warmth and body
- calm, extended listening
Consider alternatives first if you prefer
- lean, restrained bass ahead of weight
- a leaner, cooler tone ahead of warmth
A preference guide based on the existing classification. Fit and enjoyment vary with listener, music and tips.
Products to compare
Candidates selected by classification and proximity of registered reference prices, not direct A/B auditions or performance rankings.
Fit and connection checks
Information retained from registered sources. Where verified wearing photos or individual fitting observations are unavailable, consult the product photo and the specification scope.
Listening checklist
- Compare vocal masking at matched volume.
- Use familiar music to separate bass quantity from decay.
- Check treble comfort after matching tips and seal.
Cable, plugs and drive
- Earpiece connector: 0.78mm 2-pin
- Source plug: 3.5 mm gold-plated · separate 4.4 mm cable not includedSpecification source ↗
- Cable length: No established value in the checked records. Value not established · checked source ↗
- Impedance: 21Ω
- Sensitivity: 109 dB stated; reference unspecified
Included accessories
- Included accessories: IM4 earpiecesStock 3.5 mm cablePortable pouchUser manualQuick guideBrass nozzleBalanced tipsBass tipsDeep Bass tips
- Cable conductor / material: 5N OFC silver-plated copperSpecification source ↗
- Cable cores / braid: 4 cores · 392 wires totalSpecification source ↗
Frequency-response graph
MeasurementSource notes
Reading limits
These values are approximate digitization of a source image; small decimal differences should not be overinterpreted. Seal, tips, nozzle/filter, insertion and rig can change the shape. Bass speed, natural timbre, resolution, separation and stage are not established by FR alone.
Evidence at a glance
Registered source records
16
May include specifications, retail pages, reviews and notes. This is not a count of independent listening reviewers.
Specifications and sourcesMeasurement curve
Registered
Different fixtures, tips and insertion depths are not a controlled comparison. Check the recorded conditions.
Specifications and sourcesProduct video links
31
Link count is not a watched-video count. Each link states whether metadata, captions or scenes were checked.
Specifications and sourcesAssessment status
Retained editorial assessment
Signature evidence and certainty of the score are separate.
Specifications and sources- Video · linked_written_review
Home / Warm tone / IM4
Reviewed reviews
Listening review 14 · All records 20Listening review 14 · Reference 6
- 1 Fosi Audio IM4 측정치 및 노즐에 대한 고찰 ↗ · 0db.co.krReference
Exact-model title found in search. The body was not secured in this pass; listening details, author and supply relationship remain unconfirmed.
Reference link - 2 뒤늦게 써보는 Fosi Audio IM4와 ACTIVO SCOOP 간단한 후기 ↗ · 0db.co.krReference
Exact-model title found in search. The body was not secured in this pass; listening details, author and supply relationship remain unconfirmed.
Reference link - 3 1. primeaudio.org · Original source ↗ · primeaudio.orgListening reviewSource notes
Prime Audio · IM4
검정 노즐 기준 따뜻한 약한 V형, 중저음 강조와 부드러운 고음.
- 4 2. www.audiophile-heaven.com · Original source ↗ · audiophile-heaven.comListening reviewSource notes
Audiophile Heaven · IM4
유연하고 편안한 음색, 탄력 있는 저음과 절제된 고음.
- 5 3. www.pragmaticaudio.com · Original source ↗ · pragmaticaudio.comListening reviewSource notes
Pragmatic Audio — Fosi Audio IM4
따뜻한 저역과 약간 물러난 중역, 선명하되 비교적 안전한 고역의 재미있는 V형. 기본 알루미늄 노즐보다 황동 노즐이 밝아진다. 넓고 깊이 있는 무대는 장점, 엄밀한 음색 정확도와 최고 수준의 기술성은 제한적이라고 평가한다.
Fosi Audio 리뷰 제품 제공
- 6 4. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
포시 오디오 IM4 이어폰 리뷰
풍부하고 두툼하며 느리고 잔향 긴 저음, 약한 보컬 마스킹·반발짝 뒤 보컬. 넓은 공간을 자연스럽게 채우지만 완전 개방은 아님. 황동 노즐에서 보컬 존재감·부드러움 증가, 베이스팁 매칭 선호.
Fosi Audio 샘플 제공, 가이드라인 없이 작성 명시.
Read the rendered Naver article body at an existing source URL; no new search was performed.
Fosi supplied the unit; bass-tip and nozzle conditions disclosed. Notes bass masking vocals and slight vocal recession, while praising natural space.
2026-10-25 - 7 5. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
FOSI IM4 - 호방한 대륙의 기상이 느껴지는 인이어 이어폰
두툼한 저음·비교적 가까우면서 편안한 중역·열린 고역. 저역팁 사용, 황동 필터 미사용. 복잡한 대편성·후반 합창/악기 중첩에서는 규모와 공간 표현 한계.
직접 구입했다고 명시. 제품 제공·원고료 고지 없음.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 8 6. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
포시오디오 IM4 오픈백의 시원한 스테이지 사운드
블랙 노즐+밸런스팁은 풍부한 저음·중역 덜 강함·부드러운 고역의 편한 V형. 황동 노즐에서 중역 단단함과 밝고 뻗는 고역 증가. 공간감 긍정.
제품 제공·자비 구매·원고료 여부 본문에 명시 없음.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 9 7. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
Fosi Audio IM4 인이어 모니터링 이어폰
실제 청감과 그래프를 종합해 약간 중저역 강화·고역 비자극의 균형형 평가. 날카로운 강V와 거리가 있고 아주 밝은 소리 아님.
제품 제공·자비 구매·원고료 여부 본문에 명시 없음. 스펙 추론 부분은 제외하고 실제 청감 부분만 반영.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 10 8. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
26.05.05 셰에라자드 소니스토어 이어폰샵 방문 청음 리뷰
청음샵의 IM4 블랙필터: 무난한 균형과 좋은 소리 디테일이나 저음 양감 과다 지적. 나머지는 무난.
청음샵 방문 시청, 구매 리뷰 아님. T71/FiiO M21 장비와 볼륨 설정 명시.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 11 9. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
Fosi Audio IM4 후기 - 좋은 이어폰이 아니라 무서운 이어폰
음악을 해부하는 듯한 많은 정보량·분리·윤곽, 보컬 전진·충분한 저음 평가. 피곤할 수 있어 분석용으로 선호. 기존 느리고 따뜻한 합의와 차 큰 소수 의견.
구매·제공·원고료 명시 없음. 청음 장비·음원·노즐 조건 미기재, 낮은 가중치.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 12 10. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
가성비 오픈백 IEM 멸망전 HE 소교 vs 포시 IM4
HE Xiaoqiao와 IM4를 모두 들여 비교. IM4 알로이 노즐에서 저역 마스킹 정돈·정위감·개방감 긍정. 상세 비교는 예고 단계.
두 제품을 들였다고 기술하나 자비 구매 확정 고지 없음. 후속 224193315384에는 IM4를 BA 고역처럼 잘못 설명한 실질 오류가 있어 그 글의 기술 주장 가중치 낮춤.
Read the rendered Naver article body at an existing source URL; no new search was performed.
- 13 11. blog.naver.com · Original source ↗ · blog.naver.comListening reviewSource notes
Fosi IM4
조금 고역으로 무게중심이 간 무난한 밸런스, 저음 빠짐 없이 치찰음은 가끔 약하게, 자연스럽게 사라지는 울림과 넓은 공간감을 보고한다. 특출난 해상도/강한 댐핑은 아니라고 명시한다.
들어봤다는 직접 청취. 제공·구매 관계 미표기.
Existing Naver candidate articles were opened and read individually.
- 14 12. www.reddit.com · Original source ↗ · reddit.comListening reviewSource notes
Fosi Audio IM4 Review: A Bold First Step into IEMs
따뜻한 V자 음색, 펀치·극저음 울림과 낮은 중음 두께를 보고한다. 검정 노즐은 부드럽고 금색 노즐은 고음·치찰음이 증가한다. 무대는 평균보다 넓되 복잡한 합창에서 레이어가 섞인다고 실제 곡으로 설명한다.
Fosi 제품 제공 명시.
Original article body opened and read.
- 15 13. www.reddit.com · Original source ↗ · reddit.comListening reviewSource notes
Fosi Audio IM4 Review - Open-Back IEM Done Right?
일부 곡의 저음 과잉 때문에 보컬 명료도가 낮아지고 고음이 가끔 날카롭다고 보고한다. 모든 기본 팁·두 노즐을 써도 취향에 맞지 않았으며 Valorant 앞뒤 구별도 평균적이었다. Bad Guy와 Bohemian Rhapsody의 차이를 설명한다.
수 주 직접 테스트. 제품 제공/구매 여부 미표기.
Original article body opened and read.
- 16 14. note.com · Original source ↗ · note.comListening reviewSource notes
■Fosi Audio IM4紹介
따뜻하고 두꺼운 베이스에 자연스러운 보컬, 고역 반짝임과 넓은 공간. 최고 분리력이라는 평가는 아님.
Fosi Audio 제품 제공 명시.
원문 open 청취 본문·제공 고지 직접 확인 (turn699view3); 금 노즐/KBEAR07/FiiO M21, 영상 시청 아님.
Fosi Audio 제품 제공 명시.
- 17 15. cafe.naver.com · Original source ↗ · cafe.naver.comReferenceSource notes
닥터헤드폰 · FOSI IM4. 저역이 어마어마하게 부풀려져있네요
Campfire Vega 2020 직후 IM4를 들었을 때 저역이 크게 부풀고 부담스러웠다는 소유자의 인상이다. 짧은 상대 청취이며 팁·소스 조건이 없으므로, 강한 저음의 반례로 남기되 모든 청자에게 같은 양감이라고 일반화하지 않는다.
Personal purchase stated.
카페 내부 검색 후 사용기 본문 직접 열람. 구매후몇개월보관뒤재청음·직전Vega2020; 소스·팁·음량미명시.
After Campfire Vega 2020, this owner finds IM4’s bass excessively inflated and uncomfortable. It is a brief comparative impression with unspecified tips and source, supporting a bass-heavy counterpoint rather than a universal conclusion.
Original setup and disclosure (Korean)구매후몇개월보관뒤재청음·직전Vega2020; 소스·팁·음량미명시. · 직접 구매 명시
- 18 16. cafe.naver.com · Original source ↗ · cafe.naver.comReferenceSource notes
닥터헤드폰 · GEEK WOLD GK20 PRO 이어폰 사용기입니다. — Fosi IM4 비교
IM4를 밝고 탄탄하게 음이 나오는 제품으로 짧게 묘사한다. 대역별 양감이나 공간 설명이 없어 기존 따뜻한 중저음 평가를 이 한 문장으로 뒤집지는 않는다.
IM4실제청취문맥; 구매·제공·광고관계미명시
카페 내부 검색 후 사용기 본문 직접 열람. GK20PRO중심다기종비교; IM4정확소스·팁·노즐미기재.
IM4 is briefly described as bright and firm-sounding. With no frequency breakdown or spatial detail, this single sentence does not overturn existing warm, mid-bass-rich reports.
Original setup and disclosure (Korean)GK20PRO중심다기종비교; IM4정확소스·팁·노즐미기재. · IM4실제청취문맥; 구매·제공·광고관계미명시
- 19 Search scope and exclusions ↗Reference
- 20 Full Naver review scope ↗Reference
YouTube videos for this product
31 itemsVerification level: A registered link does not mean completed audiovisual analysis. Check the scope on each video.
- 1 헤드폰 같은 공간감이 예술인 10만 원대 이어폰 Fosi Audio IM4 리뷰 ↗Metadata checked · audiovisual analysis incomplete
- 2 소리 튜닝빨 제대로 받았다! 포지 첫 오픈형 이어폰 공개 " FOSI AUDIO IM4 IEM " ↗Metadata checked · audiovisual analysis incomplete
- 3 1600만원 펀딩 성공! 오픈백 인이어 Fosi Audio IM4 리뷰 | 15만원 가성비 끝판왕 ↗Metadata checked · audiovisual analysis incomplete
- 4 2가지 노즐 x 3가지 팁 = 6가지 사운드, 포시의 첫번째 야심작 | Fosi IM4 ↗Metadata checked · audiovisual analysis incomplete
- 5 결국 정착하게 되는 이어폰들의 공통점… Fosi Audio IM4 (feat.MD3) + 구독자 이벤트 ↗Metadata checked · audiovisual analysis incomplete
- 6 이어폰 하나로 6가지 소리를? FOSI IM4 & DS3 ↗Metadata checked · audiovisual analysis incomplete
- 7 $100 미만 IEM 본좌 등장, Fosi Audio IM4 ↗Metadata checked · audiovisual analysis incomplete
- 8 다기능 소형 CDP와 베릴륨 유선 이어폰의 매력 FosiAudio Merak CDP & IM4 ↗Metadata checked · audiovisual analysis incomplete
- 9 제가 들어본 차이파이 중 가장 잘만든 제품 – Fosi Audio DS3 & IM4 ↗Metadata checked · audiovisual analysis incomplete
- 10 开放带来的弥散，镀铍振膜的音色，Fosi Audio IM4 动圈耳塞快评 | TDShorts 中文台 ↗Metadata checked · audiovisual analysis incomplete
- 11 那个做了很多前端的Fosi Audio，做了一款开放式监听耳塞？！Fosi IM4测评分享 ↗Metadata checked · audiovisual analysis incomplete
- 12 Brilliantly Designed IEM: Fosi Audio IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 13 FOSI AUDIO IM4 REVIEW ↗Metadata checked · audiovisual analysis incomplete
제품/구매링크 중심 설명; 대역별 판단 미가산
- 14 Fosi Audio IM4 Review: A Bold First Step ↗Metadata checked · audiovisual analysis incomplete
동일 작성자 Reddit 본문에서 punchy bass/organic V/금색 치찰음. 영상 자체 미확인
- 15 TheHopelessGeek — Fosi Audio FIRST IEM IM4 Review ↗Metadata checked · audiovisual analysis incomplete
가격·제품 평가만 있고 대역별 청취 정보 부족
- 16 How did $100 IEMs get this good? Fosi IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 17 Fosi IM4 IEM Review - $99 Open-Back Choose-Your-Own-Adventure IEM ↗Metadata checked · audiovisual analysis incomplete
- 18 I LOVE these IEMs! Here's why... - Fosi Audio IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 19 This $100 IEM Could've Been The BEST. Fosi Audio IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 20 Fosi Audio IM4 Review — Professional, AIRY & balanced IEM ↗Metadata checked · audiovisual analysis incomplete
- 21 But Can They Make IEMs? Fosi Audio IM4 and DS3 Review ↗Metadata checked · audiovisual analysis incomplete
- 22 A new $100 FAVORITE OPEN BACK | Fosi Audio IM4 OPEN BACK IEM Headset Review ↗Metadata checked · audiovisual analysis incomplete
- 23 Are Open-Back IEMs Worth It? | Fosi Audio IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 24 Fosi Audio IM4 - In-Ear Monitors Review ↗Metadata checked · audiovisual analysis incomplete
- 25 Do These OPEN-BACK IEMs Sound Better?? - Fosi Audio IM4 Review ↗Metadata checked · audiovisual analysis incomplete
- 26 Massive Soundstage!? Fosi Audio IM4 IEM Review ↗Metadata checked · audiovisual analysis incomplete
- 27 Fosi Audio IM4 Open-Back In-Ear Monitor:ULTIMATE REVIEW // Worth YOUR Attention 🔥 ↗Metadata checked · audiovisual analysis incomplete
- 28 Fosi Audio IM4 In-Ear Monitor Headphones: The Best Budget Gaming IEMs? ↗Metadata checked · audiovisual analysis incomplete
- 29 Open Back In-Ears! : Fosi Audio IM4 ↗Metadata checked · audiovisual analysis incomplete
- 30 Fosi Audio IM4: A "Mediocre" HiFi IEM, but a GOD-TIER Gaming Earphone? ↗Metadata checked · audiovisual analysis incomplete
- 31 Fosi Audio IM4. Explained simply. ↗Metadata checked · audiovisual analysis incomplete