Letshuoer S12 PRO English Review


PRO Level At A Fair Price




Construction and Design




  • The S12 PROS are one of the fullest sounding planar IEMS I have tested to date.
  • Letshuoer has improved the frequency response in areas that were subtly critical in the S12.
  • The build quality is maintained, the cable is improved and it is now modular, with 2.5/3.5/4.4mm connectors.
  • The sound is more pleasant, harmonious and suitable for all-round and continuous use.




  • I still miss a bit more detail, a more analytical character, a bit more scene-setting and expansiveness.


Purchase Link




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Due to the sixth anniversary of the brand, Letshuoer has seen fit to revise one of its latest successful models: the S12. And of course, the model could not have a different name than the Letshuoer S12 PRO. For this new model, the highlights are the new Space Blue colour and the inclusion of a new modular cable, which can change its connectors to 2.5/3.5/4.4mm. It’s true that the changes are not only on the physical side, but the sound has also received a slight tweak. As far as I’ve been able to tell, the mouthpiece filter has been changed, resulting in some subtle alterations to the overall tuning of the set. Broadly speaking, the sub-bass has been raised slightly, resulting in a cleaner transition into the mids. The mid-highs are subtly softer and the treble has been slightly lowered in both exposure and extension. The changes may not be so obvious, but they are sure to be a clear success, as both the modular cable and the changes in tuning will be eagerly awaited by users who were still hesitant to buy the S12. With the S12 PRO version, a more accurate profile has been achieved in some critical and sensitive areas. We will see all of this in the next review.





  • Driver Type: Planar 14.8mm
  • Frequency Response: 20Hz-20kHz.
  • Sensitivity: 102dB/mW
  • Impedance: 16Ω±1%.
  • Distortion: 0.5%±0.1%
  • Cable length: 1.25m
  • Cable type: 392-wire silver-plated monocrystalline copper cable.
  • Interchangeable jack connector with a choice of 3.5mm Single Ended, 2.5mm and 4.4mm Balanced.
  • Capsule Connection Type: 2Pin 0.78mm





Not much has changed in the presentation of the new model. The Letshuoer S12s come in an eminently white box, measuring 152x104x67mm. On the front side there is a large real image of both capsules, without any cables. On the top left is the logo and the brand name in black ink. On the bottom left is the model name and on the right the Hi-Res. logo. On the back side, starting from the top, is the slogan, in larger letters. Underneath are the specifications, in several languages, including English and Chinese. From the centre to the bottom, there are the brand’s markings, more logos and the certifications that the product meets. There are also a couple of seals of authenticity.
With the outer cardboard removed, the white box is revealed with the brand name between the main face and one side. The catalogue is the first thing you can see, after lifting the lid. Underneath are the capsules encased in dense black foam rubber, located at the top. On the bottom is a transparent plastic case with foam tips inside. On the bottom is another layer of foam with the rest of the accessories. In a nutshell:


  • The 2 S12 PRO capsules.
  • 1 silver-plated monocrystalline copper cable with 392 wires and 4 strands, 2 to 2 strands, with three interchangeable connectors.
  • 1 oval, black, zippered carrying case.
  • Instruction manual.
  • Brand card.
  • Warranty card.
  • Quality control card.
  • 1 set of grey silicone tips, sizes SxMxL.
  • 1 set of transparent silicone tips with black core, sizes SxMxL.
  • 1 set of black foam tips, sizes SxMxL.


There are not many differences from the S12, the changes are subtle. I keep commenting that the grey silicone tips are too soft for my taste. But I must also comment that the inclusion of foam tips and the zippered case are to my liking.



Construction and Design


Except for the colour (Space Blue), little has changed externally on the capsules. Constructed from aluminium alloy and machined with a 5-axis CNC, the finish is smooth and micro-sandblasted. The legend on the rim, written in white ink, now includes the brand name in capital letters on the top line and the model on the bottom line, as well as the R or L channel inscription.
The capsules, on the outside, are almost triangular in shape, with very rounded corners. In reality, there is only one flat side and the rest is a single curve. The outer face is flat, but there is an overlapping rectangular piece, which houses the 2Pin 0.78mm connection. This connection is shallow and the connectors are inside a piece of translucent plastic, which in turn are inside the capsule. Next to this connection, there is a hole that goes all the way through, but is protected by an internal gold-plated grille.
After a slight edge, the rim is also rounded and the line separating the two sides is visible. There is another hole in the centre of the inner face.
The nozzles grow from the centre of the inner face, although they are not very long. They have two tiers and are 4mm high. The first tier has a smaller diameter of 5.25mm. The second and outermost tier has a diameter of 5.85mm. The mouthpiece is protected by a perforated metal grid.
All in all, the capsule lines are rounded and smooth, but the mouthpieces are somewhat short.
The cable is made of silver-plated monocrystalline copper with 392 wires and 4 strands, two by two, with three interchangeable connectors: 2.5/3.5/4.4mm. The colour is matched to the capsules. The plug is relatively large and the interchangeable connectors are press-fitted. They have 4 gold-plated pins and a guide for easy fitting. The removable part is completely cylindrical. The fixed part has a rough edge. There is a Velcro strap to collect the cable. The dividing piece is a smooth cylinder, in the same blue colour as the plug sleeve. It is 13mm long and almost 8mm in diameter. Repeated shape and appearance for 2Pin 0.78mm connector sleeves. The plastic base on which the pins sit is red for the right channel, transparent for the left channel. On this occasion, this piece is completely flat. The cable, at this end, has a semi-rigid guide on the ear. Finally, the pin is a simple piece of translucent plastic, small, cylindrical, with an 8-shaped hole inside, through which the cables pass.
The cable is now modular with 3 interchangeable pins, has more wires, but a very similar design to the S12 model.
As you can see, the changes are minimal, but the improvement of the cable and the colour change are worth mentioning. Since the mouthpiece filter has been modified, a pair or three screw-in filters could have been created, as the D13 model has, and several subtle tuning changes could have been added to the set, in one model.



Adjustment and Ergonomics


If the model is the same, the fit and ergonomics do not change. The different cable does not affect this. I still find the fit very good, the minimal rotation inside the bell is maintained. The mouthpieces are somewhat short and unchanged, there is little to comment on this. The insertion remains shallow. The level of isolation is maintained and will depend on the tips used. With my homemade foam-filled tips they have a good level of seal and occlusion. The fit, although simple, may require a little tweaking, but the sensation in the ear is very good. Both the surface and the rounded shape make contact and rubbing pleasant. Also, its contained size raises the level of comfort and ergonomics. It is pleasant to wear for hours on end and I repeat that only the weight can be a slight inconvenience if you make quick or more abrupt movements.







As I mentioned in the introduction, the S12 PRO’s profile has been accentuated at the sub-bass end, with a subtle lowering of the transition into the mids. The mid-highs have been very slightly shaded, as have the highs, which have been rounded down to between 8 and 10kHz. All in all, the U-profile has been pivoted to the bass side and the high end has been softened. There is still energy in the treble and its linearity is still maintained, but the slight adjustments in all ranges can give the impression of a more restrained touch in that upper region.
I still think both frequency responses fit my ideals. But I must admit that the S12 PRO tweaks still fit more closely with my imagined reference FR in SquigLink, even though it may be elevated in the sub-bass. But the ideal of a frequency response curve can be just that, an ideal. Because such a profile must be supported by the actual sound of the headphones. And what do we have here? Well, what I like most about the S12 and also the S12 PRO is the feeling of fullness across the entire range. Without a doubt, it’s a full-bodied, seamless, thick-as-a-wall sound. I still maintain that the S12 PROs are not very detailed, but very enjoyable, musically speaking.
Finally, I would like to talk about both the tone and the timbre of this ensemble. Natural and appropriate timbre is always spoken of, although I understand that it is never clear that this matches the reality. I myself, to be honest, might feel unable to speak accurately about these terms. Because these properties can vary greatly from headphone to headphone and many reviewers would argue that most of the time they are natural.
My idea of the S12 PRO’s timbre is its restrained and realistic nature. As I think its tuning is quite good, without seeming bright or dull to me, I think it has a neutrality that holds a bit of warmth. Overall, I find the timbre inoffensive, I don’t think about it, nor do I judge it. It’s just its timbre. And that can be a reference. I am left with the idea that things sound as they should, to a fairly large degree.





I could describe the bass of these planars as the best hybrid combination of a BA driver and a DD driver. There are characteristics from both sides. The sonority is much better than a dedicated BA driver for bass. At least in this price range. When playing pure tones, the performance can be reminiscent of the vibration of a BA in the distance. But the result is better. There is a subtle colouring that does not affect the music. On the good side is its technical ability and speed. On the dynamic driver side it acquires its physical ability, forcefulness, punch, even its colour. It doesn’t give the feeling of moving as much air, nor is it as deep, but the combination of all these aspects elevates the bass almost to the excellent.
I’m talking about the S12 PROs as if I haven’t reviewed the S12s before. Now, I take a break and reread my opinion about them. And it’s no coincidence that the idea of this planar bass keeps resurfacing in my mind. Words like precision, definition, speed, dryness, fast decay and tight execution keep coming back, both in my head and in my writing. I still miss some more roughness, texture, but I think it has gained a point of physicality, depth and overall bass presence. I’d even say it’s a little cleaner in its midrange roll-off, something that refines its behaviour. That amount of extra punch takes over my little bass-head heart and raises the score over its original siblings.
I should also point out that the S12 PROs don’t shy away from anything; there’s no hint of equivocal performance, lack of power or inability to execute saturated, dirty or dangerous bass lines without flinching, even at high volumes. In line with the best dynamic range drivers and a total reproduction insurance. Moving up.





I continue to be amazed by the planar ability to split frequencies. It is admirable to discern a hard sub-bass line from vocals and not feel that they blend at all. I think there is an improvement in that respect, without any loss of fullness in the setting. I again miss a little more definition, a little more analytical edge to bring out more obvious micro detail, but it’s still not there. I notice that I have this feeling of a complete wall of sound again, but without it being completely flat. I think there is a point of greater transparency, even if it is not its greatest virtue. Thus, there is a noticeable clarity in the vocals, and a good level of precision in the instruments. But, while everything seems to be there, everything is well executed, well presented, I’m still looking for a little more three-dimensionality and space between elements. Depth is not as evident in the mids and despite the precision of the playing and positioning, I find the volatility and gas around the voices and instruments lacking. The tuning still seems very good to me and I like the weight of male and female voices, as well as their balance with the instrumentation. A certain distance to the listener is respected, without the mids seeming too intimate and not in the foreground, but occupying a noticeable overall space between all the elements. And back to the beginning, combining and rendering all the music with a good level of presence and separately, still seems to me to be the best virtue of the S12 PRO. Now, slightly improved. And that’s what elevates these IEMS as one of the best options for many usage scenarios and music genre playback.





If the treble of the S12s already seemed good to me, it is now superior. Some peaks have been reduced and linearity has been improved, just a little bit of air has been lost. There is a slight softer nuance that gives it a superior value over the original, at least in my opinion. It’s not a remarkable change, but it is something that can be noticed over the hours, as a smoothness that allows for more extended use. The idea of a plateau persists in its presentation, allowing for a more extended travel and improved overtone execution.
The great balance between presence, precision, delicacy and sparkle of its predecessor is maintained, offering a range as a reference in the balance of energy, projection and extension, maintaining control without the need for artifice or limitation in its presence. Perhaps you might assume that such a plateau could be elevated or contain a dangerous level of power. But this is not the case for me. I prefer this more homogeneous representation, rather than inequalities that alter the naturalness of reproduction. Not that I am a staunch supporter of the flat response, but I do support this type of representation in this band, as long as the energy level is in accordance with the rest of the bands. And this is the case. The result is an exquisite example of how to reproduce sibilance: pure control and finesse. Not to mention the overall range as a whole. Within the reach of few drivers.



Soundstage, Separation


The sensation of a wall of sound offers a large and wide stage. With noticeable headroom, even. I still find that this is not the deepest, most three-dimensional, separated and airy sound in this price range. The presentation is front-facing, with a noticeable stereo feel, with great side detail. Positioning is adequate, although the relationship between elements feels somewhat fixed, without much three-dimensional space between them. Many elements remain well defined, not crowded, but feel somewhat immobile in their projection. It’s a scene that’s shown all at once, striking at the outset for its lush presentation, its ability to recreate planes and layered layering with precision and fluency. The S12 PROs have a great ability to expose many elements without blending them together and without looking fuzzy. And the better the source, the better that ability will improve. At the limit, I still miss a point of greater depth, a more oval and concave presentation, as well as a point of more air, gaseous feel and volatility. But maybe that’s the thing about such a full, complete sound.





NiceHCK F1


Again, I use IEMS which I have not yet reviewed in a comparison. Many brands have jumped on the planar driver bandwagon and practically all brands have gone for it. NiceHCK has been no less. In this sense, it’s good to see that not all planars are the same, nor do they have the same profile. F1s have something that is not unique, three mouthpieces to change the tuning. For this comparison I have used the Silver mouthpiece, whose frequency response is flatter, both in the bass and treble areas. It could be said that from 200Hz to 1.5kHz, both FRs are the same, so there seems to be some commonality in these drivers. Although the F1’s FR is flatter, its profile is brighter. While the S12 PROs have a warm neutrality and noticeable bass punch, the F1s are lighter overall, but also more defined, precise, cooler and more analytical.
There is a clear superior bass punch in the S12 PROs, as well as greater depth. Whereas the F1s are more restrained and have a thinner bass, with less attack. Technically very good and with a more detailed expression, the F1s do not have anaemic bass, far from it, but I do notice a little more colour, more finesse, less density and physicality. The S12 PROs have a wider, bigger and heavier bass range, which tends to take up more space.
In the mid-range the S12s feel more neutral, but also a little warmer. That sense of naturalness and attachment predominates. While the F1s show more luminosity, transparency, though less body as well. They are lighter and more volatile, also cooler and more expansive. I find more separation and freedom in the F1s, as well as a higher degree of resolution. There is also more joy in the F1s, despite being cooler, the notes are more sparkling, the sound is crisper, even though the FR comparison seems to have a less energetic treble. Everything is less punchy, but there is also more separation, a more gaseous and volatile sound, also more delicate and analytical. In addition, they offer a larger stage feeling. If someone thinks the S12s are brilliant, I don’t recommend the Gold and Silver filters of the F1s. But you could definitely use the Black filter.
The F1s don’t offer that wall-of-sound feel that the S12 PROs do, but they can also feel a little more muted.
On the physical side, I have had trouble finding suitable tips for the F1, their mouthpiece is not very long and perhaps the orientation is not so suitable. They weigh less though. But I prefer the more occlusive and perfect fit of the S12 PRO.
Currently, the S12 PRO are cheaper than the NiceHCK F1, but there can always be price changes and offers on both models.





The brand’s sixth anniversary has served to give one of its most emblematic models a PRO version. And they have also taken the opportunity to make some improvements to a model that was already very good in itself. I think Letshuoer has taken the pulse of the current trend by adding an improved modular cable. But they have also listened to those fans who said that the S12s were a bit shiny. For them they have redefined the FR of the new PRO model, adding a more emphasised bass at the low end, with a cleaner midrange roll-off. In addition, they have achieved a more level and neutral sound, from that middle part, all the way to the end of the frequency range. The result is a bigger, juicier, even more balanced wall of sound, with a timbre that blends a hint of warmth with the innate naturalness of the early model. The fullness, presence, impact and punch of its presentation is evident from the very first moment. It’s hard to shake off that physical, corporeal sense of density, musicality, its full, spacious stage, without ever sounding congested and everything having its living room intact. At its core, the S12 PRO sounds like live music, surrounding and totally immersive, powerful and intoxicating. But all of it inside your ears, as if it were the most normal thing in the world. And, for this price, it’s really not. The S12 PROs are still at a level that few others can offer.



Sources Used During the Analysis


  • Aune Flamingo.
  • Earmen Angel.
  • TempoTec Variations V6.
  • Hidizs AP80 PRO-X Red Copper Limited Edition.
  • ACMEE MF02s.
  • xDuoo XD05 BAL.
  • TempoTec Serenade X + iFi Zen Can.