Tribute For The Headbangers

It has been a while since we last heard from underdog brand Roseselsa, but now they are back with a highly anticipated collaboration: the Roseselsa x Andy Audio Vault (AAV) CJ20. Malaysian top audio reviewer Andy has been teasing these IEMs for some time, and after the better part of a year in development, the final product has arrived, a planar magnetic IEM built specifically for rock and metal. Inspired by China’s flagship fighter jet, the Chengdu J-20, the CJ20 brings the stealthy, robust design of its namesake to life in IEM form. Tuned for an immersive hard rock and metal experience, the CJ20 offers a distinctive sound signature that may just challenge conventional notions of neutral tuning.

A huge shout-out to Rina from Roseselsa for the sample pair of the Roseselsa x AAV CJ20 for us to have an honest take. We are not affiliated nor taken any form of monetary exchange for this review and this review is solely an honest view of the product.

For more in-depth audio reviews and portable audio content, be sure to check out Andy’s official YouTube channel, Andy Audio Vault (AAV). Subscribe for amazing insights and updates.

https://youtube.com/@andyaudiovault?si=JryP5bxxcxI4Gx7h

Functions & Specifications

Before we start the review, here are the specifications of the Roseselsa x AAV CJ20 taken from their site;

The Roseselsa x AAV CJ20 can be purchased directly from their website and many other platforms worldwide.

ROSESELSA x AAV CJ20 Planar Magnetic Driver HIFI In Ear Monitors, 1PM Wired Earphones High Fidelity with Module IEM Cable 3.5mm/4.4mm Rock Metal

Packaging & Accessories

The packaging here is actually professional yet simple with a small rectangular box that has the AAV emblem printed on them. Pretty standard packaging and straight to the point. Here’s what’s inside the box;

• 1 × Pair of Roseselsa x AAV CJ20 IEM
• 1 × Detachable modular 4-Core Cable (0.78mm 2-pin) in 3.5mm & 4.4mm
• 3 × Pairs of wide bore silicone ear tips (S/M/L)
• 3 x Pairs of small bore silicone ear tips (S/M/L)
• 1 × Carrying case
• 1 x Polishing cloth
• 1 x cleaning brush
• 1 × User instruction card

Design

The design here is reminiscent of the previous hybrid release of Roseselsa, the Star City 5 Pro but in a more refined, robust way. The CJ20 is built from aluminum alloy and they are fully metal build that is robust yet lightweight. Fit here is superb with a rather small shell that possesses great ergonomics. The overall design is classy yet futuristic and has a distinctive look, different from the CIEM meta build.

At the heart of the CJ20 is a single custom 14.2mm planar magnetic that is co-tuned exhaustively with AAV to provide a robust lows, neutral mids and lively highs to suit AAV taste for rock and metal genre. These custom drivers promise ultra fast transients with minimal distortion, producing a clean and detailed overall sound.

The nozzle here is on the smaller and shorter side with a maximum of 4.5mm width. The short and slightly small nozzles do make eartips rolling a little hard for those wide and long 3rd party eartips. The nozzles are fitted with a nylon mesh to prevent dust and moisture from entering.

There is a rather large vent with metal mesh on the faceplates of the IEM to give the planar drivers some breathing room, increasing the soundstage and air. A secondary pinhole vent is on the bottom part of the large vent covered with gold plugs to reduce pressure build up. No flex is present which is great as they are a well vented IEM but be sure to not cover the gold plugs upon inserting as it may incur some driver flex.

The CJ20 has a standard flush 0.78mm 2 pin connection that is slightly tight and they are plated in gold.

Cable provided is a high end 4 core graphene plated Ohno continuous casting copper with grey nylon sleeve. The cable is a modular cable and a 3.5mm and 4.4mm balanced head is included. The cable is slightly thin but soft and pliable suited for everyday use. The sound quality of the cable is commendable as they are a neutral sounding type that enhances the overall clarity.

Gears Used for Comparisons

Songs list

Tone and Presentation

The sound presentation of the CJ20 is a classic, aggressive V shaped tuning, almost an L shaped with a big boost in the bass and energetic highs that lean towards a mildly dark tonality. They have a good amount of warmth in their midrange with excellent extension on both ends of the spectrum that gives a wide dynamic range possessing a great amount of air. The CJ20 is a truly musical presentation and has great technicalities that balance between technicalities and musicalities but more on the latter. The overall clarity of this set is superb with a clean and clear sound profile that is detailed and mostly accurate.

Soundstage

The soundstage here is expansive with a decent width and height partly due to their semi open back style, very competent in their price range. The CJ20 possesses a good 3D holographic spatial soundstage that is accurate which makes them a good pair of IEM for gaming and movies as the sound placements are accurate. They are an intimate and immersive IEM with a free field sound that projects sound forward similar to a near field monitor, giving a rather medium sized headroom with a good amount of air.

Separation and Timbre

Separation here is great with a wide dynamic range that gives a wide stereo sound with no crosstalk issues that is able to scale up better with balanced connectivity. The tuning here is unique giving a wide dynamic range sound but there is some gap from the bass to the midrange and with certain genres, it might affect cohesion mildly. Timbre here is rich and piercy possessing great energy especially in the low range. They have the technical prowess of a planar and are tuned to be natural sounding in their timbre and they do indeed have an organic sound that is free from any weird, unnatural planar timbre.

Drivability

Rated at 24 ohms with a 102 db sensitivity, they are easily driven by any source as they don’t need much power to sound great with adequate amount of loudness but they do scale very well with higher output source that gives better dynamics and transients. The CJ20 does not pick up noise easily for their lower sensitivity making them a good pair of IEM for casual usage. Matching is important especially and pair especially well with a neutral bright source but matching with some bassy source will actually make the bass a little too strong. The CJ20 is quite revealing and they are able to show some flaws in the recording, thus a good mastered track or higher bitrates files will actually give a cleaner overall sound. These are not stage or studio monitors, instead a pair of IEMs that solely made for music enjoyment especially for rock and metal genres.

The Bass (Low)

The bass is boosted north of being neutral and they are powerful and meaty with an authoritative slam. The bass here is the dominant part of the overall presentation and it’s a basshead IEM that is not for purists as they focus on the fun aspect of music reproduction. The bass is energetic and punchy with a tightness in their slam. The mid-bass lift here is actually lifted nicely and the overall are elastic and nimble, capable of keeping up with busy tracks with ease. Though the bass is dominant, they are well controlled and possess great texture alongside good layering that shows bass nuances well, typical of a great planar bass. Details and clarity here are great, producing a clean and clear bass response. Resolution here is vivid and has a decent transparency with a fast pace enabling them to handle busy tracks without being muddy or bloaty and also no bleed is present here. The bass does have a slow roll off that gives ample amount of air. Sub-bass has a boost as well to match the overall bass but the mid-bass is still dominant. Sub-bass rumble dives deep and it has a good amount of immersive rumble..

The Mids

Midrange here has a neutral sound that is recessed but they are neutral and balanced that has a focus in the lower midrange alongside a smooth transition in the upper midrange. The midrange here has a mild amount of warmth that gives the midrange a rich sound with some lushness and they are accurate in their presentation. Details here are good with strong macro and micro details retrieval capabilities with great clarity. The recessed mids actually do push back certain sound and some sound does feel thin but on the other hand, the midrange is spacious and inoffensively smooth. The resolution here is vivid with some coloration mixed into the and they managed to sound natural/transparent. Vocal presentation is fairly balanced with their smooth highs and boosted lows, they are able to give vocals good depth but they do have an average amount of brilliance due to the smooth upper midrange. Instruments sound mostly on point but for some higher range instruments, they do lack bite or brilliance.

The Highs

The high range here is a neutral flat highs that gas great extension well into the 20khz region and they are inoffensively smooth while still having a decent presence. Sparkle here is present with a mild crispness but they do lack a lively, spicy high range despite the 2kHz spike, instead they are leaning more towards a laid-back type of high range that is fatigue free that suits treble sensitive users. Details here are good with high nuances portrayed well without any sibilance or hiss and the high range here has the capabilities to resolve high range nuances cleanly. The pace here is rather quick and they are able to play well with piercing sound like ACG or metal genres smoothly as intended and they possess a natural timbre that isn’t plagued with planar metallic overtones. Resolution here and transparency here is good and they are able to sound accurate with an organic high range timbre. That being said, for those users who seek for a smooth, fatigue-free sound signature may find these a solid choice.

Comparisons

VS Letshuoer S15 (USD250 at 2026)

My pick for best planar IEM in terms of performance. Released around 2024 with a 3D printed shell by HeyGears. The accessories included are slightly better with a hardcase but at a higher cost versus the CJ20.

High range

• S15 has better sparkly presence and bite
• Details are similar but the S15 is clearer
• Both has great extension with similar air
• CJ20 high is smoother and less piercy with a touch more air.

Mids

• S15 is better balanced with a more forward mids
• CJ20 is slightly thicker and spacious but recessed
• Details and clarity on S15 is better
• Upper mids on S15 is livelier but CJ20 is more forgiving
• Vocals on CJ20 sounds deeper while S15 excels better on female vocals

Bass

• Bass amount in CJ20 is bigger and meatier with a tighter slam alongside bigger sub-bass that dives deeper
• Bass on S15 is more neutral and sounds more natural and accurate
• CJ20 is more immersive and fun suited for bassheads

Soundstage

• Soundstage are similar with the CJ20 maybe more open sounding for their larger back vent

Vs Kiwi Ears Aether(149USD)

My pick for best Planar IEM in the price versus performance index. One of the biggest planar with their custom 15.4mm driver. Accessories included on the CJ20 are better for their modular high end cable. Fit on CJ20 is better due to their smaller shell size.

High range

• Aether has a livelier sparkle and crisper. Details and clarity are better but not as smooth as the CJ20
• CJ20 has better extension with greater air
• Treble on the Aether sounds more balanced while CJ20 is more laid-back

Mids

• Aether has more details and clarity with better transparency
• CJ20 is more resolving and spacious
• Aether has a more forward mids
• Timbre on the CJ20 is more organic
• Vocals sounds cleaner on the Aether while the CJ20 is more natural
• CJ20 able to handle complicated, fast instruments better

Bass

• The bass amount on CJ20 is bigger and meatier with more energy
• Sub-bass amount is slightly bigger on CJ20 but depth are similar on both
• Aether has a more textured, cleaner and clearer bass but lack authority
• CJ20 bass has better immersion while Aether is more natural in amount

Soundstage

• Similar in width and height but air is better on CJ20

Synergy

Good synergy: Neutral balance, bright sources

Examples: 7HZ Artemis39, Qudelix T71, Hidizs S8 Pro, Questyle M15, VE Devastator, Kiwi Ears Allegro Mini, EPZ TP30

Not so good synergy: Bassy sources

Examples: FiiO Q15, FiiO KA5, EPZ TP35 Pro

Power requirements: Easily driven with average scalability

Who Is It For?

Suitable genres: Metal, rock, hip-hop, classicals, ACG

Suitable Usage: Drummers, gaming, movies, bassheads, casual listeners

Not suitable genres: Acoustics, EDM, pop

Not suitable usage: Monitoring, critical listeners, purists, treble heads

Final words

The Roseselsa x Andy Audio Vault CJ20 is a purpose-built planar magnetic IEM that unapologetically prioritizes fun over neutrality, delivering aggressive V to L-shaped, bass focused sound with authoritative slam and fatigue-free treble specifically tuned for rock and metal enthusiasts. Its robust all metal construction reflects genuine engineering care and though the recessed mids and forgiving treble that make metal so enjoyable will naturally disappoint purists seeking analytical precision. Ultimately, the CJ20 succeeds because it pays tribute to the headbangers who want to immerse oneself in the music rather than merely analyze it, proving that specialization and honest execution still have a vital place in today’s crowded IEM market.

I would rate this product a 4 over 5 ⭐⭐⭐⭐

Pros

• Solid build with great finishing and origin design
• Lightweight & ergonomic
• Superb separation with a wide dynamic range
• Organic timbre, great musicalities
• Wide, tall and airy soundstage
• Good overall clarity and details
• Highly resolving, fast transients
• Strong, meaty, punchy dominant bass with deep, rumbly sub-bass
• Clean lows
• Spacious, natural and clean mids
• Good high range presence with smooth, fatigue-free sound
• Natural, sparkly, crisp high range
• Laid-back treble
• High quality modular cable
• Perfect for hard rock & metal enthusiasts

Cons

• Bass might be too strong for purists
• Recessed mids
• Some gaps present from bass to mids
• Mids may sound a tad thin with certain sources
• Not for monitoring
• Genre specific
• Short nozzles (nit-pick)
• A hard case would be better (nit-pick)