KIWI EARS Singolo

Specifications

Model: Kiwi Ears x Crinacle Singolo.
Driver: 11mm custom dynamic driver + KIWI Acoustic Resonance System (KARS).
Frequency response: 20Hz- 20kHz.
Sensitivity: 108dBSPL/mW.
Impedance: 32Ω.
Capsule material: Resin.
Cable length: 1.2 meters.
Connection interface: 0.78mm.
Plug type: 3.5mm SE.



The Kiwi Ears x Crinacle Singolo is another collaboration from Crinacle with his signature sound and an interesting innovative technology the (Kiwi Acoustic Resonance System).
The Medical grade resin is comfortable and despite the short nozzles I found the isolation good as well as the fit. The Singolo comes with the units, a cable and some tips. accessories are sparce and the silver-plated cable is just fine but nothing special. It does have those odd 7Hz style curved horn shaped two pin connectors. The Singolo has a 11mm custom LCP dynamic driver that was made in Japan for them.





Here are my impressions of the Kiwi ears Singolo:

Bass: is the subject of focus here. The 11mm driver and Helmholtz resonator give a clean and deep Bass response with Sub-Bass front and center with good depth and a healthy rumble, Bass in general is well textured and Mid-Bass has a speedy and notable impact but is not the most accurate.

Midrange: While not the most technical the Mids do have a natural tonality and present almost Neutral. There is a little recession in the lower Mids and a mild warmth, upper mids are transparent and neutral for the most part. body and vocal energy are above average.

Treble: The Highs are relaxed with a decent but lackluster amount of energy and sparkle, there is enough air and details but ultimately it is a smooth and relaxed extension.

Soundstage: Is decently Wide with less depth and good imaging and separation. this is not a technical IEM but it does good enough here.

Equipment Used:
I use a large variety of devices but mostly I used the Fosi SK02, Burson Funk, Tempotech V6, Pixel 8 pro, Pixel 7, the Questyle M15, ifi GoBar, Diablo-2 and Gryphon for most of this.

My final thoughts:
I like the enjoyable signature of the Singolo for Jazz and K-pop music, not that it didn't work on rock and Pop, but I think there are others in the price range that do a better job. that said the Bass is fantastic on these. I think they would be a good travel companion.

It is very likely that your experience with this IEM would be very different from mine.

The most tricky thing about reading and writing reviews of IEMs is that they are personal audio devices. The “personal” aspect here goes beyond one’s preference for a a particular musical genres, a band, or a singer. No. It’s the shape of one’s ears, the place where they listen to music, the device from which they get the audio signal, and even the loudness at which they listen that paints a very different sonic picture for each listener.

That has been the case for every IEM, but these new IEMs from KiwiEars, the Singolo, are more challenging than most. It is a shame because behind the challenging fit lies an impressive skill in shaping the frequency response of a dynamic driver that is almost unseen until now.

Forewords​

• What I look for in an IEM is immersion. I want to feel the orchestra around my head, track individual instruments, and hear all of their textures and details. I’m not picky about tonality, as long as it is not make the orchestra, violin, cellos, and pianos sound wrong.
• I rate IEMs within with a consistent scale from 1 (Poor) to 3 (Good) to 5 (Outstanding). An overall ranking of 3/5 or above is considered positive.
• Ranking list and measurement database are on my IEM review blog.
• Terms used in my reviews are consistent with the glossary by Headphonesty
• This review is based on a review sample from Linsoul (Thank you!). I have no affiliation with or financial interest in Linsoul or KiwiEars.
• The unit retails for $79 at the time this review was published. Unaffiliated link: https://www.linsoul.com/products/kiwi-ears-x-crinacle-singolo

General Information​

At the heart of Singolo is a single 11mm dynamic driver (DD) with a Liquid Crystal Polymer (LCP) diaphragm. You might have already heard LCP drivers in some Sony IEMs or the classic Moondrop Aria 2021. The diameter of the DD is slightly larger than usual, but other than that, its simply a decent DD. The way KiwiEars tunes this driver is where things get interested.

Looking closely at the transparent shells of Singolo, you would see an 3D-printed sound tube connected to the back vent of the DD. This tube folds upon itself multiple times before connecting to a small vent hole on the IEM shell. KiwiEars calls this system “Kiwi Acoustic Resonance System” (KARS).



You might ask: “what’s the big deal?”

I’m glad you asked. Let me geek out a bit. If you have ever dabbled in DIYing a pair of flathead earbuds or modding your IEMs, you would have undoubtedly engaged in tuning DD to reach an agreeable frequency response. The thing about DD is that there is not much you can do (or at least I can do) to force it to conform to a target, besides applying a parametric EQ profile. Here are some ways you can tune a DD:

• Change the driver: each driver has its own characteristics and idiocrasies that you can take advantage. Ideally, you would want a driver to be as close to your ideal sound as possible as the starting point.
• Change the shells: unlike balanced armature (BA) drivers, DD relies a lot on the shape of the shells, particularly the acoustic chamber that holds the driver. For example, in the flathead earbuds world, one of the trick is drilling a hole at the back of the shells to create a bass tube at the back of the driver (are you seeing that KiwiEars KARS resemblance?)
• Chock the back vent with filter: As you know, a DD generally has an opening at the front to release the sound and a vent hole at the back to release or balance the pressure behind the diaphragm. When the pressure is higher, the diaphragm is more “dampened.” One way to increase this pressure is to put a thicker filter to “choke” the driver. This trick makes it harder for the DD to vibrate, which can lead to “tighter” transient response.
• Chock or open the front vent next to the nozzle: this prevents the excess pressure from escaping, significantly increase the midbass and lower mid. Alternatively, you can increase the openess of the front vent to reduce the bass.
• Putting foams and filter in the nozzle: this might be the most familiar trick used by manufacturers. The idea here is to cut back the energy in the treble region. If you can change the inner diameter of the nozzles, you can change the shape of the upper midrange too. Again, for amateurs like myself, this activity is more trial and error than exact science.

Looking at these options, it’s obvious that KiwiEars has applied the first option by choosing a particular LCP driver for this project. The KARS system simultaneously implements all of the remaining options to shape the frequency response of Singolo. Here, instead of using a filter, KiwiEars use the air volume inside the KARS tube to dampen the back vent. In conjunction with another tube at the front of the DD to release excess energy coming out of the DD, KiwiEars can precisely fine-tune the response of the DD without relying on any foam or nylon filter, thus preserving the integrity of the transients.



Another purpose of the KARS tube is acting as a Helmholtzs resonator. As you can see, when the diaphram inside the DD vibrates, it would vibrate the air volume inside KARS tube. When it vibrates, it can make sound (think of the time when you blow air across the opening of a bottle). By carefully control the parameters of this resonator, KiwiEars can push the resonance frequency of the system down to the subbass region. Another IEM utilising this technique was AFUL Magic One.



In summary, by careful manipulation of the KARS tube, KiwiEars managed to create a single DD IEM that is tuned almost identically to “well-tuned” multi-driver IEMs, such as Monarch MkII from subbass up to around 6kHz. And they did it without any electronic crossover, any foam or nylon filter.

To me, this is quite a feat of engineering.

Non-sound Aspects​

Packaging and accessories: Quite modest. In fact, I would say Singolo is downright below average on this aspect. Inside the small box, you have the earpieces themselves, a flimsy 3.5mm cable, and two sets of ear tips that likely wouldn’t work with your ears.



Ear pieces design: This is where all of the woes of Singolo come from, in my opinion. On the plus side, the earpieces are quite small and smooth, so they wouldn’t create any ear pain. On the negative side, the nozzles of Singolo are simply too short. Moreover, the bulk of the DD tend to force the nozzle to sit at a slightly awkward angle. As a result, short ear tips likely fail to seal because they don’t reach deep enough into the ear canals. Longer ear tips might not be able to seal either due to the angle of the nozzles. As you know, if you cannot get a seal, an IEM is not usable.

Ear tips recommendation: Let me describe how the lack of seal sound before we talk about some good ear tips. With the stock ear tips, I cannot consistently seal the ear canal, leading to a “no-bass” experience. With SpinFit CP100 and W1, the stickiness of the tips make it feels like I have achieved a decent seal, and it is true that I can hear some bass. However, there is a strange hollowness in the lower midrange, and the soundstage feels oddly wide but hollow. Moreover, the upper midrange can sound harsh with some tracks.

In the end, I settled for two options:

• Comply foam tips
• Divinus Velvet silicone tips

Driveability​

Singolo is not hard to drive. Its impedance (32ohm) and sensitivity (108dB/mW) are neither too high or too low, putting it within the sweat spot of many portable DAC/amp devices. However, it does sound better with better DAC and more powerful amplifiers. Using Victory (Live) from the Live album by Two Steps from Hell as an example, I hear the following changes:

• Apple dongle: Singolo sounds acceptable but not particularly interesting or good. “Slightly mushy” would be the keyword that I use to describe the presentation across the frequency spectrum.
• HiBy R3II (4.4mm, high gain): The mushiness is mostly gone. I also start to hear some resemblance of depth and layering in the stereo imaging (i.e., separation between closer and further sounds in a mix).
• iBasso DX300 (4.4mm, medium gain): Singolo sounds quite good. The bass line is highlighted. Bass attacks feel sharper and more defined. Instruments are more spread out across the stage.

Subjective Experience​

Testing setup:

• Sources: DX300
• Cable: NiceHck Black Cat 4.4mm
• Ear tips: Comply foam tips

Timbre, tonality, and tonal balance: Singolo embodies the almost cliche “well-tuned” signature with a distinct bass shelf, flat lower midrange and a slight tilt toward the upper midrange. However, it lacks the treble extension after around 8kHz. I sometimes joke that this IEM is a simulation of hearing lost that younger audiophiles would eventually have.

In practice, it means this IEM is unlikely to sound “wrong”, unless you haven’t been able to achieve a proper seal. The piano in Goldberg’s Variations by Lang Lang sounds balanced and realistic, making it relatively easy for me to follow individual voices. Tokyo Kosei Wind Orchestra sounds correct and natural, though lacks a certain “shine” that I expected due to the more subdued treble response of Singolo (no, silicone tips do not improve the situation here).

However, the timbre of the violin is a bit off, as if there is a bit imbalance towards the upper midrange and likely a bit too much energy around the 3kHz, when I listen to four seasons by Janine Jansen and ensemble. The same observation was found when I listen to Bomsori: Violin on Stage album. The situation was a little bit better with Bach: Sei Solo by Leonidas Kavakos. Still, if you pay a lot of attention of violin, this IEM is not an ideal option.



The theme of slightly unbalance midrange carries over to vocal musics. For example, when I listen to = album by Ed Sheeran, I miss a bit richness in his voice and find that the shoutiness of his voice was highlighted more than my preference. At the same time, there is a lack of “shine” of high-frequency energy. To put it bluntly, Singolo makes this album sounds a bit dull. On the plus side, it provides a very comfortable listening experience, almost free of sibilance even with harsh recordings in this album like “Shivers.”

In summary, I would consider the tonality of Singolo to be good (3/5).

Bass and perceived dynamic: The bass of Singolo is a highlight of its presentation. For instance, when I listen to Gundam Build Fighter OST by Yuki Hayashi, I can hear and feel positive and definite “thumps” from the bass line. Some tracks such as Iori Hobby Shop is downright entertaining with Singolo due to the physical sensation of the bass notes. My only complain is that the perceived dynamic of Singolo is not as impressive as bass response. Simply put, the transients (volume spikes) are not snappy and sharp, likely due to the more subdued treble response.

Still, I would say the bass of Singolo is pretty great (4/5).



Resolution: To me, “resolution” can be broken down into three components: (1) Sharpness, incisiveness, or “definition” of note attacks (see the figure above). (2) The separation of instruments and vocals, especially when they overlap on the soundstage. (3) The texture and details in the decay side of the notes. The first two give music clarity and make it easy to track individual elements of a mix. The last provides music details and nuances.

To be honest, I’m a bit disappointed by the resolution of Singolo. Whilst the zero dampening design does a decent job at preserving the micro details at the decay end of the notes, the perceived resolution was held back by the weaker performance of both the definition of note attacks and separation of instruments and vocals. In direct comparison against the Moondrop Aria, I was disappointed to find that not much progress has been made on the resolution front.

At the end of the day, the resolution of Singolo is acceptable (2/5), but uninspiring.



Stereo imaging and soundstage: Stereo imaging or “soundstage” is a psychoacoustic illusion that different recording elements appear at various locations inside and around your head. Your brain creates based on the cues in the recording, which are enhanced or diminushed by your IEMs, your DAC, and your amplifier. In rare cases, with some specific songs, some IEMs can trick you into thinking that the sound comes from the environment (a.k.a., “holographic”)

There are not much to say about the stereo imaging ability and soundstage shape of Singolo. The stereo image is not blurry but not particularly pin point. The soundstage is mostly in the head with more width (left-to-right separation) than depth (front-to-back separation) and height. Layering is not significant due to the weaker instrument separation. Even when boosted by the DX300, the stereo imaging and soundstage of Singolo is acceptable (2/5) but left me wanting more.

Multimedia usage: Given the uninspiring soundstage performance with music, I did not have much expectation for the performance of Singolo in FPS gaming. However, I was pleasantly surprised by how competent it is. In both CS Go and CS2, I can sense the direction and distance of the sound from all angle, even the front where most IEMs tend to sound flat and closed in. The muted treble response also reduce fatigue.

Frequency Response Analysis​

Frequency response of Crimson against Helios and the Harman in-ear target. Measurements were done with an IEC-711-compliant coupler and might only be compared with other measurements from this same coupler. Above 8kHz, the measurement might not be correct. Visit my graph database for more comparisons.



It is helpful to think of an IEM as a filter that highlights or subdues different parts of the incoming audio signal. This effect can be measured objectively by the squiggly lines above, called Frequency Response (FR) graphs, which measure how loud an IEM is at different frequencies from 20Hz (bass) to 20kHz (upper treble). Subjectivity is how your ears and brain interpret the effect of that filter on your music and decide whether it is “enjoyable.” There are some “rules of thumb” when it comes to tonality, but most interesting IEMs usually bend the rules masterfully.

Usually, I would have elaborated analysis and discussion. However, I think the graph speaks for itself in this case.

Conclusions​

I’m conflicted about the Singolo. On the one hand, it demonstrates a fascinating level of technical expertise that is objectively verifiable. On the other hand, beside the great bass response, the actual sonic performance does not reach beyond the “acceptable” level established by the old guards like the Moondrop Aria. And then, we have the fit problem mentioned by many users. Whilst I’m very enthusiastic about the technology and technique presented here, I cannot recommend Singolo in 2024 unless you are would like to support the company and the tuner.

What I like about this IEM:

• Bass
• Technology

What could be improved:

• Fit
• Lack of treble energy

Absolute Sonic Quality Rating: 3/5 - Acceptable

Bias Score: 3/5 - I’m lukewarm about this IEM



Updated: May 12, 2024

Introduction

Kiwi Ears are a small international group of engineers with the sole aim of producing the best sounding audio solutions for musicians and audiophiles. They focus on developing the latest driver technology innovations with refined tuning strategies that reveal all the nuances of music and performance. This time, they have collaborated with Crinacle, one of the world's most reputable audio critics, to create the new Kiwi Ears Singolo. The Singolo is a custom 11mm dynamic driver IEM featuring the revolutionary Kiwi Acoustic Resonance System (KARS). KARS is a discrete bandpass filter that manipulates the airflow to the driver, regulating the low-frequency output. This patented innovation features an elaborate labyrinth-like network of tubes that has been designed based on numerous scientific and physical models to perfectly calculate the right resonance point for the Singolo transducer. The KARS makes a tight subwoofer shelf possible, something that was previously impossible in a single-transducer IEM. Unlike traditional crossover filters that use multiple transducers with RC (resistor-capacitor) networks, KARS uses Helmholtz resonance to regulate their tuning. The airflow to a dynamic transducer regulates how much the diaphragm can respond, but also requires additional calculations of flow rate, direction and volume. The KARS allows precise regulation of this airflow to manipulate the sound as desired. While capacitors and resistors provide a calculated medium for crossover solutions, they also add unwanted artefacts to the sound in the form of distortion, especially when using cheap SMD components. With KARS, the sound you hear comes directly from the transducer itself, resulting in a pure, higher resolution audio experience without the encumbrance of passive electrical components. KARS is 3D printed to an accuracy of 1.0 micron. The Singolo incorporates a custom Japanese liquid crystal polymer (LCP) diaphragm driver. This 11mm dynamic transducer has been custom created for the KARS, with unique front and rear acoustic chamber profiles. The Singolo is tuned according to Crinacle's tonal signature. It is a synthesis of all the best tuning profiles found in the world's most successful headphones over the years. With an 8 dB sub-bass boost, the bass is incredibly punchy and powerful, but cuts off impeccably at 300 Hz. This allows for a neutral midrange that articulates the natural sound of vocals and instruments without any artificial distortion. The treble follows the perfect compensatory curvature of the pinna, with a clean peak at 3 kHz and a natural roll-off into the upper treble.
After all that talk, let's see how the Crinacle Kiwi Ears Singolo really perform.



Specifications

• Model: Kiwi Ears x Crinacle Singolo.
• Driver: 11mm custom dynamic driver + KIWI Acoustic Resonance System (KARS).
• Frequency response: 20Hz- 20kHz.
• Sensitivity: 108dBSPL/mW.
• Impedance: 32Ω.
• Capsule material: Resin.
• Cable length: 1.2 meters.
• Connection interface: 0.78mm.
• Plug type: 3.5mm SE.
• Mouthpiece inner diameter: 4mm.
• Suitable ear tip size: 4-4.5mm.
• PRICE: $79.00 USD.

Packaging

The Kiwi Ears Singolo comes in a medium-sized box with a mix of blue and black background. Its dimensions are 146x122x38mm. On the main side you can see, at the top, the logo of the brand and also the Crinacle logo. In the centre there is a real photo of the capsules on gold ink brushstrokes. At the bottom is the model name and a short description of the model, all in white ink. On the back, at the top left, are the logos of all the certifications held by the product. To the right is the brand logo in large print. In the centre, the model name and description are repeated. At the bottom are the brand name, e-mail address, web address and distributors. Removing the cardboard cover reveals a black box with a silver brand logo in the centre. After opening the lid you can see the IEMS with the cable inside a black foam mould. Underneath is a black cardboard lid with the brand logo in silver. Under that cardboard is the rest of the cable and accessories. In a nutshell:

• The Kiwi Ears Singolo x Crinacle.
• A silver-plated single-strand cable coated with clear PVC.
• Three pairs of black tips sizes SxMxL.
• Three pairs of white tips sizes SxMxL.
• One instruction manual.

And nothing else. For a set costing around $80, there is no storage bag or pouch. The cable is just average, with a tendency to stiffness, although I like the curved design of the plug sleeve, as well as the 2Pin 0.78mm connectors, and the cylindrical metal cover installed on all these parts. The tip set is standard, completing a limited accessory set for the price.



Construction and Design

The capsules of the Kiwi Ears Singolo are made of resin. They do not have a semi-custom shape, but a classic one, with a triangular outer shape with rounded corners and a smooth, but continuously curved inner side. The outer face is blue on a fluid micro glitter base that varies in shades of blue to white, with almost pinkish tones in between. In the centre is the brand logo in silver. The capsules are relatively thick compared to the small-medium size of the set. The inner face is completely transparent, emphasising the visibility of the internal construction and those ducts that make up the KARS. You can see a duct that connects the driver output face to the base of the driver and then that labyrinth-like duct that connects a plate above the base to the output at the edge of the capsule. Enlarging the photo you can see the steps of the KARS made with 1 micron precision. The driver is relatively large, 11mm, coated in metal, while on the side near the apex you can read the name of the brand written on that cylinder. The inner side is very rounded and the transparency allows you to see the driver diaphragm at the base of the mouthpiece. The mouthpiece is metallic, with a minor diameter of 5.3mm and a crown of approximately 6.55mm. The total length is around 4mm and they are protected by a multi-perforated metal grille. Finally, the 2Pin 0.78mm connection interface is fully integrated into the rim of the capsules and is gold-plated.
The cable is a simple transparent strand whose conductor looks like silver-plated copper. It is somewhat stiff although not very thick, which is classic when it comes to this translucent PVC coating. All connector sleeves are curved and made of a whitish plastic. They are small parts with a cylindrical metal cover. The gold-plated 3.5mm SE plug is located near the cable outlet. On the 2 Pin 0.78mm connection interface it is at the base of the two gold-plated pins. The pin is at 90 degrees while the sleeve of the 2Pin connectors does not reach that many degrees, although it is clearly curved. The splitter is a smooth metal cylinder and the pin is a translucent plastic piece with a double through-hole. It is effective enough to hold the adjustment.
As you can read in the introduction, Kiwi Ears seems to have gone all out on the interior design of the capsule, with the patented KARS replacing any electronic crossover filter. In the end, it looks like a simple labyrinthine duct that has been seen in other IEMS. Otherwise, the capsule's exterior design is pleasing, very rounded, with generous nozzles in diameter although somewhat short. The cable, given the price and the scarcity of accessories, could be better. There is no choice of balanced plug.



Adjustment and Ergonomics

The size of the capsules is small-medium, somewhat thick. Their weight is very light. All this, together with a very rounded shape, fits very well in the pinna. The problem comes with the diameter of the mouthpieces and their length. Their projection is very good, as is their inclination. But the thickness can be a bit big for some ear canals. Not for mine, whose diameter is quite large. Using my large tips filled with a lot of foam, I get that classic occlusive and long-lasting surface insertion. The good shape of the capsules limits rotation and the isolation, using my homemade tips, is very good. However, it is clear that the use of these specific tips, together with the diameter of the mouthpieces, can lead to some fatigue over the hours, despite the large size of my ear canals. Nevertheless, the ergonomics are more than remarkable and quite durable.



Sound

Profile

The profile of the Singolo is somewhat peculiar, oscillating between a V-U, with that excitement in the sub-bass and midrange. However, the highs are quite nuanced and, perhaps, that is the crux of the matter. Thanks to the KARS, the bass is the star of the show. Designed to sound like a subwoofer, the Singolo's bass is big, voluminous and wide, even if it has a distinct drop-off as it enters the low-midrange. The first half of the midrange feels a little sunken and the midrange stays there until a gentle rise up to 4kHz. From that point on, there is an abrupt drop and the treble softens up a lot. It is not a dark profile, but rather a more nuanced and softened profile in brightness, sounding a bit dry and sparse, a bit forced.
Finally, the Kiwi Ears Singolo are somewhat difficult to move.



Bass

Without a doubt, the bass of the Kiwi Ears Singolo is big and voluminous. The low end is certainly intrusive and permeates the entire soundstage. It's a bass with range, medium speed, that lingers in the room. It is relatively agile, but its strength and effect is felt in the air and in volume, it stays in the head and is not so quick to collect itself. This makes the spin more impressive, but the hit is effective, well-drawn and very punchy. It is not a dry hit, but juicy, but relatively well defined. It has a good dose of texture, plenty of bounce and power, both physical and sensory. And that shows in the very low frequency pure tone test. The low end is quite sensory with an audible undulating part. But, that sensory point possesses a good degree of power that comes to stun, like a dull kick. You can clearly perceive the power in the sub-bass and its sensory power. As the frequencies increase, this energy becomes more audible, but remains shattering and vast. Are the Singolo IEMS for bass heads? From their overwhelming behaviour in the sub-bass, I would say yes. That mix of sensory and physical power, coupled with the volume it generates, makes me think it can be included in this category.
Finally, in the test of dirty bass, unfiltered bases, complex and mixed bass lines, the Singolo's proved remarkably adept. Despite the grandeur of their bass, it is true that their intonation stops at the point where the midranges begin. From 20Hz to 250Hz there is a 10dB drop designed to deactivate the bass in the midrange. Does it succeed? It's tricky, but it works up to a point. On the plus side, the Singolo's are able to execute complex passages with a good level of definition, without clumping and without sounding drowned out or muddy. Admittedly, there is a lot of rumble and it is not one of the fastest basses to recover. But there is some ability to follow the lines, as long as they are not too fast. But, it is also true that the lines can get stuck together due to their own power and the volume they occupy in the atmosphere. This makes it not the cleanest when it comes to reproducing fast bass lines or layers. But, so much power is not easy to make disappear.



Mids

The brand itself says that "the bass is impeccably cut at 300Hz. This allows for a neutral midrange that articulates the natural sound of vocals and instruments without any artificial distortion." The truth is that the first half of the midrange feels relatively sunken, more so, if the music has bass. In electronic music with vocals it is clear that the power of the bass affects the ambience and tends to crowd out the vocals. For a male range that already feels medium-distance, with a lean body, a somewhat dry sonority due to limited harmonics, the Singolo would not be the best choice if you want to enjoy it. When the bass is not very present, there is a tendency to want to turn up the volume to bring these male voices closer, because their sonority, although somewhat sparse, is felt in an analogue but muffled way. This implies a release of full sibilance, but leaves them with an unjuicy, mostly dry, dark-leaning body. On the other hand, the female voices don't stretch towards brightness either, despite the emancipation of the pinna gain. It is true that they are favoured, but they remain on a plane that is not entirely protagonist. Feminine sibilance can become subtly visible in those songs prone to it. But it's a thick, rounded, nuanced sheen, never penetrating, and brief.
In the rest of the instrumentation, this dull, dry, nuanced quality persists. In my opinion, the natural sound is more vivid and also more sparkling, without being annoying, of course. However, the Singolo's are too secure in this respect, as well as being somewhat distant. Do they sound good? As I say, there is a tendency to turn up the volume to enhance the fullness of the midrange and, as long as the bass doesn't appear, they can come across as fuller and more balanced. At that point, more enjoyable midranges appear, slightly soft, dark, yet musical. But that does not detract from the imbalance in the bass.



Treble

To describe the high end, I refer again to the manufacturer's notes: "The treble follows the perfect compensatory curvature of the pinna, with a clean peak at 3 kHz and a natural decay towards the upper treble". Are the treble natural? Perhaps I could say they are naturally smooth. It is true that I have been commenting that the sound is muffled, dry and nuanced, that the harmonics are not felt very much. However, if we talk about pure treble, it is true that it is there and expressed in a more natural way than I had thought. With that initial peak at 4kHz and a steep drop of another 10dB, the treble is stretched into the air zone by means of a controlled undulation. The result is a high end that doesn't have a lot of energy, but is more homogeneous and realistic than expected, sounding smoothly natural and analogue. It is also descriptive and extensive enough to provide a good level of information. The downside is that the treble also feels a bit off from the midrange, hence the harmonic hollowness in the central range. In addition, their low energy also means that more power is needed to perceive them individually. The effect on the rest of the music is that their presence is relatively average.



Soundstage, Separation

The scene is predominantly frontal, a clear sense of volume at the bottom giving it a good level of depth. However, it is not too wide. There is a correct lateral sensation and not too much headroom. The feeling is of a more compact and unified sound, where the separation is not very obvious, nor is the layering or stratification. Beyond the volume and space occupied by the bass, the midranges feel homogenous and fairly cohesive, something that keeps the sound from being too technical or possessing too much resolution. If the songs have enough treble, the ensemble responds in a more airy way. Otherwise, the feeling of dryness, sparse and relatively dark sound, will detract from the detail. With corresponding power, detail can come to the fore and the sound becomes cleaner. But, even in that scenario, the detail is somewhat coarse and not very well defined, declaring a medium resolution and a rather average technical behaviour. It is clear that the Singolo are more musical and fun in their bass section, than technical.
The image is just OK and not very remarkable in this department either.



Comparisons

TKZK Ouranos

The TKZK Ouranos struck me as IEMS that were in the middle of the tuning of the late 2022 and early 2023 TinHiFi's (T2 DLC 2022, T4 Plus, C2 and C3). They were the softest in treble and with a bass in the middle. Personally, I have to say that I liked them a lot. Their ergonomics are a notch above the Singolo, due to their semi-custom shape. The cable is almost on a par, although the Ouranos is stiffer. In terms of accessories, both are very sparse, but the Ouranos come with a small cloth bag. The current price of the Ouranos is $55 compared to $79 for the Singolo.
What can you see from the comparison of the two frequency responses? You could almost say that the Ouranos are a Singolo with a softened subwoofer. Their curve is more balanced and rounder, with slightly more irregular treble. Subtly more sensitive, the Ouranos' profile seems more homogeneous, balanced and fuller. There is some similarity in the way the bass of the two IEMS performs, neither is too fast and the power control found in the Ouranos gave it a certain amount of joy and vigour. In the Singolo this character is clearly enhanced and it does feel like a more exaggerated Ouranos in the sub-bass, but also less compact and staying more in the room. The LFOs work quite well on both IEMSs, executing the pure tones very well, but with that familiar sensory and physical superiority of the Singolo. But so much power is difficult to dissipate and with a texture that is also complex to smooth out.
The midrange is more disconnected from the bass on the Ouranos, but they have that nice, musical warmth, which gives it more body, a more physical part and more presence. The first half of the midrange is closer in the Ouranos and male voices appreciate it. In the Singolo there is a point of sinking in that first half of the midrange, which unbalances the central range, leaving a certain gap. At that point, the Ouranos seem more natural and with better timbre. They are relatively equally dark. That they are thinner in that first half gives a point of clarity to the Singolo, less warmth in exchange for being leaner and thinner. That warmth of the Ouranos is also transmitted to the midrange and the female voices also feel fuller and rounder. I think the midranges, despite the dark and warmth of the Ouranos, are better than on the Singolo. However, the highs of the Singolo are better achieved than in the Ouranos. They don't sound the same, despite the similarity. I find the high end of the Ouranos a bit more strident, while the Singolo's treble reproduction is more homogeneous, even coherent. In the Ouranos I feel a certain disconnection in some points, while the Singolo show a more balanced behaviour throughout the range.
On a technical level the Ouranos dare to hint at the micro level. Despite the darkness and its softness, there is more space between layers and a richer background can be glimpsed. In it, certain details can be noticed. Those same details are more buried in the Singolo's because they sound flatter and tighter. That level of layering gives the Ouranos more of a sense of depth throughout the range. Therefore, I think there is a point more resolution and detail, even though the Singolo's seem more defined because they are thinner.
The scene is more voluminous in the Singolo, but I find the presentation of the Ouranos to be more spacious, with that better layering. Their better balance between bands means that, by giving them more power, there is no imbalance and you can see the size of their scene and better laterality.



Conclusion

Every brand seeks to innovate and in this regard, I find Kiwi Ears' work in creating the KARS commendable. It is clear that their bass is distinctive, creating IEMS that combine a power for bass heads, along with a tuning that tries to be smooth and natural. Thanks to the KARS, the Singolo's bass comes close to the behaviour of a subwoofer. But that very power makes them a specialised IEMS, which distinguishes them from an all-terrain IEMS. Kiwi Ears may have sought to create IEMS for bass heads, but without sacrificing a certain degree of naturalness and realism. In this sense, it succeeds in the treble. However, the clear intention to disconnect the bass from the midrange makes the first half of the middle range relatively hollow. On the other hand, it is more musical and smooth than technical. And in the price range in which it moves there is a lot of competition with very good resolving abilities. But I think the Kiwi Ears Singolo need not compete with them, but with that other IEMS range for bass heads that lacks that more audiophile level. The Singolo's niche is in that area, not in the wide range of IEMS based, more or less, on the Harman curve. And that is where they excel and should be taken into account.



Sources Used During the Analysis

• Hidizs S8 Pro Robin.
• EPZ TP50.
• Burson Audio Playmate 2.
• Aune X8 XVIII Magic DAC + EarMen ST-Amp.

Purchase Link



You can read the full review in Spanish here