The Letshuoer S12 PRO has been a reference single-driver planar-magnetic IEM since they launched in 2022. Featuring a substantial 14.8mm planar-magnetic driver, it excels particularly in bass performance. The housing is crafted from CNC-machined aluminum alloy and is both compact and comfortable. Additionally, there is a supplied high-quality cable equipped with exchangeable termination connectors.
LETSHUOER S12 PRO SPECIFICATIONS
- Driver: 14.8mm planar-magnetic driver
- Impedance: 16Ω±1Ω
- Sensitivity: 102dB
- Frequency Response: 20Hz – 20KHz
- Distortion: 0.5% ±0.1%
- Connector IEM: 0.78 dual pin
- Cable termination: 2.5mm / 3.5mm / 4.4mm swappable
- Cable: 392-strands silver plated monocrystalline copper
- Chassis material: Aluminum alloy
- Machining process: 5-Axis CNC
- Accessories: Memory foam, standard and transparent ear tips. Each set comes in three sizes. Cable and adapters. Faux leather carrying case
LISTENING IMPRESSIONS
I used two amps during this session: The RME ADI-2 DAC FS as a DAC/amp and the Sparkos Gemini hybrid tube amp with the RME as a source.
Georgia Lee by Tom Waits
The S12 PRO renders Tom Waits’ voice with lots of texture. All the ambient sounds and details are presented clearly. It’s a coherent and balanced delivery.
Graceful Touch by Tord Gustavsen Trio
This piano trio piece sounds very good, the bass has lots of texture and definition. The piano is very crisp and clear, with a very upfront tone. The soundstage and imaging are decent.
Merciful by S. Endresen and N.P.Molvær
This very short, slow female vocal-oriented jazz track sounds good, but there is a slight dryness to the vocals with the RME. It’s not an issue with the Gemini amp. The singer’s voice is very textured, and it balances on the right side of sibilance.
Midnight City by M83
The S12 PRO handles the complexity of this track well. The bass is very satisfying, laying a foundation for the rest of the music without dominance. However, again, there’s this slight dryness with the RME amp but not the Gemini. The separation of instruments is good.
Sit Down Stand Up by Radiohead
Everything is nicely balanced. The bass is especially impressive. It’s very tight, and there’s a lot of texture. Vocals and percussion are quite crisp, occasionally bordering on sibilance.
Terminal 7 by Tomasz Stanko Quintet
The percussion is very snappy. The trumpet has lots of nuance and texture. The bass is felt as an inspiring force rather than stealing the show. Imaging is good. Cymbals might sound a tad splashy with the RME, but not with the Gemini amp.
Viaticum by EST
Again, the bass is impressive. It’s not massive, it’s just there. Like a foundation for the rest of the music. Well defined and not in any way overpowering the music. The piano is very crisp and clear. I like the S12 PRO, especially with the piano.
Young Vivaldi RV 813 I. Allegro by Ensemble Modo Antiquo
The strings have a lot of articulation, texture, and bite. There’s good separation, and the presentation is quite upfront-sounding.
COMPARISONS
KIWI EARS QUARTET vs S12 PRO
The Quartet is a large resin-body IEM with a dedicated mini subwoofer. It has two tuning switches, which give a total of four optional tuning variations. I keep it in stock configuration only (bass on, treble on / 1-1) for this comparison.
The S12 PRO and the Quartet have a very similar sound signature. The Quartet has a slightly softer treble but a similar amount of presence, something you might appreciate if you are sensitive to crisp treble. The bass and midrange presence are also very similar.
S12 PRO is cleaner and clearer sounding. It does, however, have a slight dryness to its mid-range that the Quartet doesn’t have.
Basically, the S12 PRO is the next step up from the Quartet if you want a similar sound signature and, importantly, have a relatively powerful amplifier. The Quartet is easier to drive.
In terms of practical differences, the Quartet is significantly larger. It is actually a very large IEM. However, it does have tuning switches, which is a plus. The S12 PRO comes with a much higher quality cable with replaceable termination jacks.
- Buy on Linsoul: Kiwi Ears Quartet
- Buy on Amazon: Kiwi Ears Quartet
SIMGOT EM6L vs S12 PRO
Like the S12 PRO, the Simgot EM6L has a sound signature with elevated bass and treble. However, they diverge in the treble response, where the EM6L is closer to the Harman 2019 curve.
Further, they have different strengths. The S12 PRO delivers a tighter bass and crisper midrange, albeit occasionally verging on sibilance in the treble. On the other hand, the EM6L offers a slightly fuller bass and warmer midrange, as well as a more balanced treble response not prone to sibilance.
The EM6L has slightly better macro-dynamics, particularly in the bass, while the S12 PRO excels in explicit detail and micro-dynamics. The S12 PRO leans towards a drier, more textured sound, while the EM6L provides a slightly warmer and more organic timbre.
- Buy on Amazon: Simgot EM6L
- Buy on Linsoul: Simgot EM6L
SENNHEISER IE200 vs S12 PRO
The Sennheiser IE200 also features elevated bass and highs with relatively less pronounced mids. However, there are significant differences in how they sound compared to the S12 PRO.
The IE200 offers smoother-sounding treble compared to the S12 PRO, which tends to be crisper and more pronounced. It is often perceived as brighter and is more vulnerable to sibilance.
In the midrange, the IE200 exhibits a velvety, polite character, while the S12 PRO delivers crisper, more textured midrange with better articulation, albeit at the expense of smoothness.
The IE200 boasts a more powerful bass in the lowest regions, whereas the S12 PRO offers more detail, texture, and a generally tighter bass response.
Regarding soundstage and imaging, these are relatively similar, with the S12 PRO feeling slightly more open and often more precise with regards to imaging, seemingly due to its crisper sound.
They are both detailed, but the S12 PRO has stronger microdynamics, sounding crisper and more textured, while the IE200 presents detail in a smoother, more refined manner with a more laid-back feel.
- Buy on Amazon: Sennheiser IE200
SENNHEISER IE600 vs S12 PRO
The IE600 is the IE200’s bigger brother. They share the same driver but have a different housing with slightly different acoustic tuning. The IE600 is also made of 3D printed metal while the IE200 is all plastic.
As with the IE200, compared to the IE600, the S12 PRO has a wider soundstage, and the bass is less full-bodied. The S12 PRO also generally is brighter-sounding. The IE600 has significantly more refinement in the treble region, and except for the wider soundstage, I prefer the IE600 overall. It’s like an IE200 with better bass and treble definition.
- Buy on Amazon: IE600
AMPLIFICATION
Most people will, of course, use the S12 PRO in a portable setup. Even though I tend to use my desktop rig because of convenience and to be absolutely certain to give the IEMs I am testing the best possible source, it is of course not necessary to use a desktop tube amplifier to make the S12 PRO sound great.
My good old LG V40 phone, known for having one of the best headphone outputs of any smartphone, just didn’t cut it. It gets loud enough, but details and dynamics are seriously lacking.
I tried the XDuuo Link2Bal but only in unbalanced mode, and that didn’t cut it either. I assume it’d be a lot better with the more powerful balanced output
The AudioQuest Dragonfly Red is a powerful and slightly warm-sounding USB dongle that pairs very nicely with the S12 PRO. It certainly delivers a warm tonality, but it also delivers the amount of detail and dynamics needed. Another USB dongle that does the job is the THX Onyx. It’s almost on the same level as the Dragonfly, although not quite as warm-sounding. Both dongles’ volume stay at 50-60%.
WRAPPING IT UP
Sound Signature
The Letshuoer S12 PRO has a strong bass, elevated highs, and relatively less presence in the mids, a tuning that is quite typical of many modern IEMs.
Treble
The treble is crisp and clear, with a good amount of detail and articulation. However, there are sometimes tendencies toward sibilance, and occasionally I can find it a bit splashy. This depends on the amplifier, though. With several solid-state amps, the S12 PRO can sound a bit dry, but with the Rebel Amp or especially the Sparkos Gemini, the treble is quite liquid and smooth.
Midrange
The midrange is detailed and has lots of texture. It can, however, like the treble, sound a bit dry with certain amps. With warmer sounding solid state amps, or even better, the Sparkos Gemini hybrid tube amp, I think the midrange is great. I don’t think it’s correct to call the midrange of the S12 PRO “warm sounding”, although the bass gives the total experience a warm feel. Many IEMs have a more organic sounding midrange, but the S12 PRO is great for what it is: Crisp, clear and textured.
Bass
The S12 PRO has fantastic bass quality, with excellent definition, and a very textured presentation. In terms of quantity, the bass is powerful, but without stealing the show. It is never bloomy or bloated, always tight. Even though the bass is elevated, it sounds quite natural and has the right presence.
Soundstage and Imaging
The soundstage of the S12 PRO is quite open, and the imaging is pretty good for this price range. There are better IEMs for imaging, if that’s very important, but the S12 PRO is absolutely adequate for most listeners.
Detail, Dynamics and Timbre
The S12 PRO definitely can throw a punch and offers well articulated details. It’s not a smooth and lush sounding IEM, though. In terms of timbre, the S12 PRO is a bit on the dry side. It depends a lot on the amp, but there’s probably always going to be a hint of that dryness. Not that it’s a bad thing, that tonality is what gives the S12 PRO such a high sense of raw texture.
CONCLUSION
The S12 PRO delivers an impressive bass that is both powerful and tight. The midrange is crisp and clear. The treble is detailed and energetic without becoming too bright, even though it occasionally verges on sibilance.
With regards to timbre, it’s more textured and crisp than organic and smooth. Sometimes it can feel a bit too dry, but this depends on the amplifier. I found it very enjoyable with warmer-sounding amplifiers, especially my Gemini tube hybrid. The S12 PRO needs some power to shine.
If you pair the S12 PRO with a matching amplifier, it’s a great IEM with impressive bass control and a genuinely engaging presentation.
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