The Fosi Carbon 12 (Carbon12) is a single dynamic driver in-ear monitor (IEM) priced at 149 USD.
It has a 12 mm dynamic driver with a carbon diaphragm and a dual-chamber design. Fosi claims the Carbon 12 is the world’s first IEM with a UTPT diaphragm. “Ultra Thin Ply Technology” results in an unusually thin and rigid diaphragm.
The shells are made of titanium alloy and have a rectangular design.
FOSI CARBON 12 SPECIFICATIONS
- Type: in-ear monitor
- Driver: 12mm dynamic driver with UTPT™ thin-ply carbon diaphragm
- Impedance: 37 ohms
- Sensitivity: 108 dB/Vrms
- Frequency Response: 20Hz–40kHz
- THD ≤ 0.5% @1kHz
- Cable: silver-plated oxygen-free copper cable
- Cable connectors: 2-Pin 0.78mm
- Cable termination: 3.5 mm jack
- Housing Material: TC4 titanium alloy with carbon fiber faceplate
- Balanced eartips, bass eartips,treble eartips
- Tuning foams & tweezers included
- Travel pouch
- Weight: 7.5 grams (per earbud)
Disclaimer: The review unit was provided in exchange for an honest review.
- Fosi Audio: Carbon12
BUILD AND DESIGN
The Carbon 12 features unusually shaped rectangular shells that are slightly rounded on the inside. They fit well in my ears, although fit is always a personal matter. In my case, I wouldn’t want them to be any larger.
The shells are made from TC4 titanium alloy, with carbon fibre backplates. Besides adding a nice visual touch, the carbon fibre has acoustic benefits, as it is non-resonant. Despite their solid construction, the shells are very lightweight at just 7.5 g.
The Carbon 12 comes with a nice silver-plated OFC cable that uses 0.78 mm 2-pin connectors and terminates in a 3.5 mm jack. It is light and flexible.
An unusual feature of the Carbon 12 is that it comes with replaceable nozzle tuning foams. There are three types of foams: low, medium, and high density. There’s also a pair of tweezers included to help you swap them. Higher density softens the upper treble, while lower density adds more brightness. I didn’t try tweaking the sound with the foams, nor did I feel the need to, but it’s great to have the option.
There are three types of ear tips included, in three sizes each. They are claimed to offer different bass responses, but differences between tips are usually subtle. I didn’t test them myself because I used my own third-party tips, as I always do to ensure optimal fit.
A soft, envelope-style black pleather storage and transport pouch is also included.
LISTENING IMPRESSIONS
Associated equipment:
- Amplifier: Topping A90
- DAC/Amp: Ferrum Erco mk2
Alt e bra by Building Instrument
Very pleasant tuning. The highs are detailed but not sharp or fatiguing. The bass is powerful enough without being too dominant. The midrange is nicely present. It all feels very neutral and natural.
In the Mountains by Espen Eriksen Trio
Very nicely balanced. The bass is powerful enough, the piano is delicate but nicely present, and the treble is detailed without being overly bright.
Re-Melt by Tord Gustavsen Trio
Again, I really like the bass. It’s nice and warm, but not too much so. The piano is very natural, and the percussion is relatively snappy but still smooth.
Teardrop by Massive Attack
Tight but quite full bass. Spacious, very pleasant sound profile. Delicate vocals without sibilance.
The Hidden Camera by Photek
Rich but tight bass. Percussion is textured but not dry.
Spontaneous Compositorius by Thomas Agergard
Very pleasant, nicely balanced. The bass is rich, the saxophone is natural, and the percussion is not overly bright.
Eye of The Day by Marta del Grandi
The vocals are warm and upfront but still have nice texture and nuance. The instruments are well balanced, and everything feels coherent.
Come Away With Me by Norah Jones
Here too, the vocals are upfront in a very nice way, and the mix feels coherent.
Sujet Tabou by Renaudin and Cahours
This is a very dynamic track with percussion and acoustic guitar. It feels natural and coherent, but not as explosive as I have heard it on certain other earphones.
Limit to Your Love by James Blake
Vocals are great. They can often sound a bit too bright and crisp, but not with the Carbon 12. The bass can be a real challenge, but the Carbon 12 does a good job.
Like Suicide by Soundgarden
Very good. Slightly dark and with a warm low end, but not muffled or unclear.
Vicarious by Tool
The rich low end suits this track well. It’s also not sharp or dry, rather on the darker side, but in a good way.
Never Enough by Loren Alred
The vocals on this track can often sound bright and sharp, but not with the Carbon 12. They sound natural and very good.
Young Vivaldi by Modo Antiquo
Nicely warm and rich string timbre.
Summer 3 Vivaldi Recomposed by Max Richter
The Carbon 12 definitely gives one of the warmer and darker renditions of this track, but it still works well, in a smooth and laid back manner.
WRAPPING IT UP
Sound Signature
The sound signature is neutral to warm.
Treble
The treble is detailed but slightly laid-back in a nice way.
Midrange
The midrange is full and rich while retaining good detail.
Bass
There’s a nice bass shelf, but it’s not overly boosted. It feels warm and rich, but also tight and punchy.
Soundstage and Imaging
The soundstage is reasonably large, and the imaging is quite good.
Detail, Dynamics, and Timbre
The detail level is very good for the price, but it is not always overly articulate. The sound signature makes detail come through in a smoother rather than sharper manner.
Dynamics are good but not extraordinarily impressive.
Timbre feels natural across the frequency range, in a neutral, slightly warm manner.
COMPARISONS
Associated equipment:
- Amplifier: Topping A90
- DAC/Amp: Ferrum Erco mk2
SIVGA LYREBIRD vs FOSI CARBON 12
The Sivga Lyrebird is a quad-driver hybrid IEM that uses four drivers of four different types. It has an aluminum alloy housing with a wooden faceplate and is currently priced at around 149 USD, the same as the Carbon 12.
The Fosi Carbon 12 and Sivga Lyrebird are close in both build quality and sonic character, but comparing the two side by side, the Lyrebird is a bit spicier and more energetic, with slightly more bass and a sharper treble. It also has slightly stronger dynamics, often a bit better articulation, and generally offers a larger sense of space.
The Carbon 12 is the more neutral and smooth of the two, with richer, more forward mids, a slightly more laid-back treble, and what I find to be a somewhat more accurate and neutral timbre.
Both are great options at the 149 USD price point.
Read full comparison here:
Sivga Lyrebird vs Fosi Carbon 12 Comparison Review
- Amazon: Sivga Lyrebird
- AliExpress: Sivga Lyrebird
- Sivga: Lyrebird
CONCLUSION
The Fosi Carbon12 is a well-built IEM with an unusual rectangular shell design. They fit me well, but might be a bit large for some users.
The sound is on the warmer side, with excellent rich mids and a detailed but slightly laid-back treble. The bass is a bit elevated, but sounds very natural.
The Carbon12 isn’t the most technical and spicy sounding IEM, but it’s still very capable, with great detail, nice imaging, and good dynamics.
I really like the Carbon12 IEMs, and if you’re after a neutral-to-warm tuning, it’s an easy recommendation.
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- Fosi Audio: Carbon12
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