Welcome to META Sound

Ratings

Pros

• Very full sound based on the META curve.
• Good level of energy in the bass.
• Density, homogeneity, fullness in the mids, very enjoyable.
• Safe tuning.
• Comfort and ergonomics.
• Great sound level for the price.
• Excellent soundstage.
• Can be purchased in a pack for very little extra with the Allegro Mini dongle.
• The Allegro Mini dongle has two SE and BAL outputs for a very low price, plus a design that is very suitable for use with a smartphone.

Cons

• Can be soft in treble or dark.
• Single set of tips.
• Shallow case in relation to the size of the capsules.
• Soft micro detail, not an analytical profile.
• The Allegro Mini dongle has a somewhat fair power rating.

Purchase Link

https://www.linsoul.com/products/kiwi-ears-ke4

Link to the Store

https://www.linsoul.com/

Introduction

Kiwi Ears, the Shenzhen, China-based brand, has been among the first to jump on the bandwagon of the so-called META frequency response. This new reference curve has emerged thanks to Brüel & Kjaer’s new high-frequency head and torso simulator model 5128. The new measurements made with this new headband simulator have sparked a new debate in the world of headphones, as well as a revolution in what the new reference frequency response should look like. One way to simplify all this is to come to the conclusion of that response called META. And the Kiwi Ears KE4 has been tuned based on that frequency response. Actually, it’s not the first or the only one, but the KE4s follow that current trend that raises the bass, narrows and balances the vertical range of that frequency response, smoothing and homogenising bass, upper midrange and treble. The result is a tuning with a powerful base, upper midrange and smooth, slightly dark treble. Is this curve the new neutral reference? I would never have come to that conclusion with my ears. But, I must admit that neutral references have always been too bland for me and I welcome a more bass-juicy and balanced reference, as META represents.
After all this, it is worth noting that the Kiwi Ears KE4 are IEMS whose design starts from scratch. It integrates an isobaric subwoofer system of two 10mm dynamic drivers combined with two BA drivers, one full-range (RAB 32257) and the other used for the treble (Knowles RAD 33518). The KE4s feature a three-way passive crossorver and three independent sound tubes, which allow for precise frequency separation and mixing. The housings are made of durable medical-grade resin, while the faceplates are hand-finished.
As if that wasn’t enough, the Kiwi Ears KE4 can be paired with a small dongle called the Kiwi Ears Allegro Mini for just $10 more. This dongle costs $24 and is a curious T-shaped device with a USB Type-C connection in the centre of a bar with different audio connections (SE 3.5mm and BAL 4.4mm) at each end. It supports PCM 32bit/384kHz and DSD128 audio resolution.

Specifications

• Driver Type: 2 DD 10mm for bass, 1 custom BA RAB-32257 for midrange and 1 BA Knowles RAD-33518 for treble.
• Sensitivity: 102dB (±1dB).
• Impedance: 28Ω.
• Three-way crossover frequency.
• Jack connector: SE 3.5mm gold-plated.
• Cartridge Connection Type: 2Pin 0.78mm.
• Starting price: $199 (Kiwi Ears KE4), $223 (Kiwi Ears KE4 + Allegro Mini). Special set price $209.
• DAC: Built-in DAC/Amp chip.
• THD+N < 0.004% (32Ω load, A-weighted).
• Output power: ≥ 30mW (32Ω, THD+N < 1%).
• SNR: ≥ 114dB (32Ω load, A-weighted).
• Frequency response: ±0.2dB (20-20KHz).
• Noise floor: < 3μV (A-weighted).
• Supported Formats: PCM (up to 32bit/384kHz), DSD (DSD128, DSD64)
• Output: USB C to 3.5/4.4mm.

Packaging

As this is a double review I’m going to be a little more concise. The Kiwi Ears KE4 come in an eminently black box, measuring 131x112x66mm. On the main side is the brand logo at the top, the slogan on the right, a realistic photo in the centre and the model name at the bottom. The lettering is white and the design is in BN. The specifications are on the side, while the back side contains information about the brand and the certifications the product has. Once the cardboard is removed, the box is black with the brand logo in the centre in mirror silver ink. The IEMS are embedded in a foam plate lined with black cardboard. On the second layer is the brand’s classic case, in a narrow version, inside a foam mould. The complete contents are as follows:

• The two Kiwi Ears KE4 capsules.
• A black zipped case.
• One user manual.
• One 4-strand cable with SE 3.5mm connector.
• One set of white silicone Kiwi Ears Flex Eartips.
• Two pairs of filters for mouthpiece protection.

A single set of tips is too little for a 200$ model, even if they are of a particular model. On the other hand, brands should think about people with larger ear canals, because, unfortunately, even the L model doesn’t fit my morphology. The zippered case is too narrow for the size of the capsules. The brand itself has thicker cases that would have been more convenient. The cable is good, but I still miss a balanced version. Very fair accessories for the price.

The Allegro Mini comes in a small white cardboard box whose dimensions are 67x67x16mm. There is a drawing of the product profile in the centre of the main side, the logo is at the top and the model at the bottom, all in black lettering. On the back there are the brand’s contact details. Inside is a black card with product specifications in several languages. The dongle is inside a black foam mould. There is nothing else, no cables, no USB Type-A adapters.

Construction and Design

The capsules of the Kiwi Ears KE4 are made of black medical-grade resin, while the outer plates are hand-finished. The capsule design is semi-custom, yet thick, and the mouthpiece is short and metallic, in two steps. The inner diameter of the mouthpiece is 5mm, while the crown measures 6mm. The 2Pin 0.78mm connections are gold-plated and are embedded in the capsules themselves, so that they remain shallow. The outer face may be reminiscent of the African continent, albeit narrower. They are silver and shiny, with the logo engraved in the centre. On the rim of the capsule, on the narrow side, there is a regular hole protected by a metal grid. The inner side is ergonomically shaped, but without raised protrusions. The mouthpieces are slightly projected on an inclined base. They are made of metal and protected by a metal grid with straight grooves. On the inner side of each capsule is written the text C-1563 and the letter indicating the channel underneath, in gold ink.
The cable has four intertwined strands, each with a dark copper colour. The plug sleeve is a smooth, shiny metal cylinder. It has a recessed ring on the side of the 3.5mm SE gold-plated connector, while the other end has two and a transparent plastic shield that protects the cable outlet. The splitter piece is of the same type, but half the size. The pin is a shiny metal disc with two holes inside, it does a good job of fitting the cables, as it is not easy to slip. The sleeves of the 2Pin 0.78mm connectors are two smooth, shiny cylinders, with two slots near the cable exit, where their shape becomes slightly conical. The two pins are mounted on rectangular black plastic bases. The cable has ear guides.

The Kiwi Ears Allegro Mini is a slim, rectangular pickup with a lightweight, micro-sandblasted aluminium alloy housing. It features the brand logo in a depressed circle in its centre. On each narrow side face are the audio outputs. The 4.4mm balanced output is gold-plated, while the 3.5mm SE output is not. The USB Type-C connector is in the centre of the long side, while on its back is a black piece that also reaches the audio connections. On the underside of the dongle is engraved the model name. The dimensions of the rectangular dongle are 38x16x12mm excluding the USB connector, while if you count the width it reaches 24mm.

Adjustment and Ergonomics

The capsules are thick and have a pronounced semi-custom shape. They have a slender outer side, while the curves of the inner side are not very pronounced, so they are not too obtrusive. It is clear that they are looking for a coupling in our pinna, but, because the mouthpieces are short and not very projected, the insertion is quite shallow, at least in my case. In this way, the capsules anchor themselves quite naturally and smoothly to the outer parts of my ears. There is hardly any rotation once seated and the fit is occlusive and very durable. Being made of resin, their weight is low, which prolongs the comfort of the set. Despite their thickness, the integration with the cable is very well achieved and they are very suitable for daily and outdoor use, as well as for long listening. The level of insulation is high.

Allegro Mini Measurements

The specifications of the Allegro Mini dongle claim a power of 30mW, but do not specify the output, either SE or BAL. My measurements give a value for SE with no load of 0.94V RMS, while with a 33Ω load, the output is 0.925V RMS, which produces a power of 26mW RMS.

 
For BAL the output is just as powerful. With no load 0.94V RMS, with a 33Ω load it gives 0.927V RMS, which generates a power of 26mW RMS.
To give 30mW power at 32Ω 0.98V RMS is needed. The Allegro Mini is close.
On the other hand, it is strange that the power is the same for both SE and BAL outputs, when normally twice as much power is achieved by BAL. So one can wonder how this balanced output is actually implemented.

Finally, as can be seen in the pictures below, the output impedance for SE and BAL are less than 1Ω, which is very much appreciated.

 
In conclusion, the Allegro Mini is capable of driving the KE4s with ease, but 1V is a low output for some of the harder IEMS to drive. You could say it’s the standard minimum.

Sound

Profile

Well, the profile of the Kiwi Ears KE4 has been based on the new META curve achieved thanks to the new Brüel & Kjaer model 5128 high-frequency head and torso simulator. Transposed to our classic IEC60318-4 01 Occluded-ear Simulator microphone, the frequency response has a maintained emphasis on the sub-bass all the way to the mid-bass. The mid-range roll-off is slight and remains smooth from 200Hz to 20kHz, avoiding the classic IEMS V-shaped dip. The upper mids are slightly emphasised, while the entry into the treble is subtly decreasing down to the air zone. The amplitude of the entire frequency range is 10dB, which indicates how balanced the KE4’s response is. All this, extrapolated to music, implies that the KE4 has a strong, deep base, with balanced, even mids and smooth highs. Some might say that this is a somewhat dark sound, but it is not deliberately warm, although it is more so than bright. It is definitely a full, dense and complete sound.
For the following review I have used several dongles to maximise the potential of the KE4s and compared the Kiwi Ears Allegro Mini against another dongle in its price range.

Bass

Using a good source you get the full potential of the Kiwi Ears KE4. Where, at first, using the Allegro Mini, I felt the bass was a bit rubbery, springy and slower, with the Go Bar Kensei it feels very dry, precise and faster. True, the texture also becomes smoother, but it feels more technical, skilled and capable. I go straight to the very low frequency pure tone test expecting a great result. And so it is, at the 20Hz tone you get that mix of sensory vibration, barely audible, deep and far from unreal vibrational character. As the frequencies increase, the power and density rise, while maintaining that natural, deep and physical perception of the bass. Undoubtedly, the KE4s have a great behaviour when the source allows it, generating pure, firm, real, powerful and deep tones, far away from any unnatural vibratory character. It is canonic bass, but extended, with more body and volume. Its power is relatively high, I could never say that it is a neutral bass, because it has a very good presence in the overall music and quite a lot of punch. But it is also true that it appears when it is needed and has a great respect for the rest of the frequencies. Perhaps it is not the cleanest bass against the mids, as it drags body and warmth in that initial part of the central range. But that’s just the search for a much fuller, denser and more complete midrange. On the other hand, it could also be said that it is not the darkest of the basses and that is conditioned by that extended curve towards the mid bass. However, this gives it that extension, punch, body and volume to the range, but it also penalises it a little in terms of dissipation speed and presence in the environment. Those looking for that clean, completely dry, ambient-friendly bass may find the presence generated by the KE4 too much. But it’s also something that can be corrected with a bold source. As always, in that balance is the presence of texture, fun, elasticity, rumble, power, volume on the one hand and dynamism, decay, speed, dryness, resolution and precision on the other. The KE4s lean towards the first side and I like that.
In the unfiltered bass test, the quality of the KE4s is evident, showing itself to be skilful and very capable in the worst conditions. It is adept at recreating complex and dirty bass lines, maintaining control in the most difficult situations, always sounding natural, restrained, but powerful. Perhaps the bass is more noticeable than sensory, but even in this less advantageous scenario the KE4s don’t let up. In this delicate test, the bass generated by the KE4s never seems invasive, overbearing or unrealistic, drawing lines and layers that are very natural sonically, knowing how to stratify the bass drums and separating it from those dirty continuous bases. You even get the feeling that KE4 get better the more time they spend in this swampy, complex terrain. Excellent.

Mids

It is in the mids that this new META tuning is a success. Fans who have been reading my previous reviews will have noticed that one of the terms I have been repeating lately has been ‘hollowness’. In classical tunings, the upper mids are often emphasised in search of ‘forced’ clarity and transparency. On the other hand, the lower mids feel light, thin, lacking in body and physicality. And that’s something that creates that hollow feeling that I abhor. Sometimes it can be fixed by adding warmth and softening the upper area. But many times it results in a dark profile that doesn’t resolve the situation, and even harms the clarity of the sound. However, I think the KE4s have found the perfect balance throughout the range. I perceive the male voices as full, with a very precise, natural and realistic timbre. They have a deep, full, dense base, but never sound muddy or too close. Their presence is broad, balanced, complete from the base to the harmonics, showing their whole composition in a precise and homogeneous way. Best of all, this perception extends to all the instruments based in this first half of the mids. A real pleasure.
On the other side are the female voices. Being a purist I am obliged to say that they sound a little drier, warmer and with less sparkle. Maybe it’s habit, but my ears are more accustomed to perceiving that more vivid point of brightness in them. By contrast, the upper mids are neutral, subtly dark, but very musical. The female voices gain in texture, offering a richness in their base that I have rarely enjoyed. In their details, the projection is more restrained, with a more limited and less fine extension. Those looking for the metal edge in guitars won’t find it here, as the KE4s offer a much more restrained, drier, less juicy and very little splashy sound. Sibilance tends to zero and brightness is soft, though it’s not a dull sound by any means. The virtue of the KE4s’ upper mids is their level of resolution. Despite that wiry musical feel, the upper mids are not sterile, withered or wilted. Perhaps the more appropriate term is ‘neutral’. And anyone who doesn’t see it that way should look the other way.
It is only after a few hours with the KE4 and a good source that one realises the absorbing, three-dimensional capacity of its midrange. It is a very pleasant place, very musical, rich, immersive, surrounding and full of space, depth, without being analytical, cold or piercing. Perhaps, to put a downside, the micro detail is not the most resolute and you have to look hard to find it.

Treble

It could not be otherwise. The treble is somewhat softer and more nuanced than what I would consider neutral. I miss a little more sparkle and a slightly finer, sharper, more delicate and energetic presentation. Even so, the treble maintains a natural, slightly warm, calm and subtly thick sonority. It is a treble that does not crunch, but retains a good level both representative and informative, without losing sight of the extension or the level of resolution. In this way, it is very easy to succumb to this musical sonority.
Again, the surprise comes when playing my test tracks for treble: at first I missed that more penetrating brilliance. But as I played back the songs I realised that the KE4’s treble is much richer and more realistic than I first perceived. In Crescendo.

Soundstage, Separation

The Kiwi Ears KE4 are outstanding on soundstage. Without being too big in size, the surrounding and immersive feeling is something that grabs you. It’s easy to feel at the centre of the music with a good source. Thus, the scene can be perceived as semi-spherical, even slightly more so, with an incipient perception under the feet and better over the head and behind it. The sense of space and separation is evident, without being incoherent or exaggerated. On the other hand, the sound is deep, dynamic, with fast transients, tonally accurate and timbrally realistic. Perhaps it could be said to be a little dry in that respect. But the level of musical richness and the very pleasant feeling it provokes make these minor shortcomings forgivable. Including certain limitations in the expression of micro detail. The balance, the homogeneity and the size of the music make us forget those aspects more common in more analytical and cold profiles. Not forgetting that we are talking about $200 IEMS.
On the other hand, the positioning of the elements is surrounding. It is not too ethereal or vaporous to appear diluted, but the KE4s maintain a high level of cohesion to draw them in a concrete and precise way, displaying an excellent level of resolution. In this way, the elements have a real, corporeal and perceptible form. This reinforces the very natural immersive feel of the music.

Comparisons

Yanyin Aladdin vs Kiwi Ears KE4

Maybe the META curve didn’t exist, but warm and soft tunings in upper mids have always existed. And the Yanyin Aladdin was one of those models. Released in 2021, the Aladdin is a hybrid with 9.2mm 1DD and 3BA. They have a semi-custom shape and are built in resin, similar to the KE4, but are smaller. They came with two sets of tips, a leather pouch and a silver plated cable. Their starting price was around $250, if not more. But more expensive than the KE4’s. In terms of integration and ergonomics, the slightly smaller size makes the Aladdin’s integration in my ears somewhat better.
In terms of tuning, the Aladdin’s bass is subtly cleaner. They have a little more meat in the midrange, while the upper midrange is smoother, as well as the treble, with less extension than the KE4s. They need less energy to generate the same sound pressure.
The low end is very similar. The pure tone test establishes this. But the KE4s have a bit more body, darkness, volume, energy and rumble. The Aladdin’s are a bit cleaner and drier.
The Aladdin’s higher energy between 1000Hz and 2000Hz pushes the male voices, even partially the female voices, a bit more than the KE4s, achieving a bit more clarity in that respect. Then, despite the Aladdin’s lower energy in the upper mids, they sound very clean, close, transparent and clear. This is surprising comparatively speaking. The KE4s have denser mids, with more weight, with a more physical low end, even a bit darker. The Aladdin’s sound a bit freer.
The Aladdin’s highs seem more nuanced, but they have a bit of a highlight in the first highs, compared to the KE4s, so the sonority is not quite the same. After that, the KE4s have better extension and their sonority ends up being more coherent. I think there is a bit less control in the treble of the Aladdin.
The sense of density makes the KE4s seem to have less separation, but the scene is bigger, once you get inside their music. The perception of detail is very similar in both models. That softened, nuanced feel, with that darker, warmer point persists in both models and the micro detail suffers, though it’s noticeable in both.

Hidizs SD2 vs Kiwi Ears Allegro Mini

The Allegro Mini DAC/AMP is really cheap ($24) for having SE and BAL outputs. It’s a pity that it doesn’t have much power (just under 1V RMS and 26mW RMS according to my measurements for 33Ω). The Hidizs SD2 is priced at $40 and provides higher power (1.5V RMS and 68mW RMS for 33Ω by my measurements). But it has only one SE output. Both have a mic line and can be used with a cable that has a built-in mic. The Hidisz uses the ES9270 DAC, while Kiwi Ears does not specify the chip model used.
Is there much difference in sound between the two? No. The Allegro Mini drives the KE4s well, but for more demanding things I prefer the SD2 with more than twice the power.
One thing that can be a nuisance on the SD2 is the Fade-In it has when playback starts.
In the very low frequency pure tone test the behaviour of both is very similar. They are not the most controlled and realistic LFOs among the dongles I have, but the performance is very similar. Perhaps there is subtly more control in the SD2. The result is an adequate bass, without too many frills, tight and well executed in both models.
In the mids the Allegro Mini seems a little warmer, while the SD2s seem to have a point of better definition, a little more separation and transparency. That warmth of the Allegro Mini limits the stage feel, even sounding subtly more faded. The SD2s have a bit more light, a higher point of definition and resolution. And that’s something you notice in the mids and highs.
Macro detail is evident in both products, but the darker, better-defined background of the SD2s gives them an advantage when it comes to reproducing micro detail, which is sharper and more polished.

Conclusion

The new Meta reference curve has been one of the most talked about events in the audiophile world. Since then, a number of products based on it have started to emerge. The Kiwi Ears KE4 is one of them. Based on a great low end, with a dense and full transition into the upper mids, upper mids and smooth highs. The KE4s are very solid, homogeneous, balanced and full IEMS. For some, they may be dark and bass-excited. For me they are IEMS that fill the hollowness and emptiness I find in the lower mids of many models, while maintaining a remarkable level of energy in the bass. All of that is to my taste, including the smoothness in the upper mids and the balance in the treble. Perhaps I miss a little more sparkle or analytical ability. But, for now, in this price range you still have to choose between one thing (analytical profile) and the other (warmer, more musical profile). What is beyond doubt is how much I enjoyed listening to music while writing this review of the Kiwi Ears KE4. And I can’t always say that. Perhaps that’s the best praise.
On the other hand, the Kiwi Ears KE4 can be purchased in a bargain-priced bundle with a dongle called the Allegro Mini, just $10 more. Priced individually at $24, this dongle has a T-shape that houses the USB Type-C connection in the middle, a 3.5mm SE output on one side and a 4.4mm BAL output on the other. It’s capable of delivering 1V RMS on both ends and generates pretty good sound for its price, on par with slightly more expensive dongles. They may not be good enough to extract the full potential of the KE4s, but they can be a very economical, if not the cheapest, option with SE and BAL outputs, plus cable support with microphone. Little more can be asked for that price.

Sources Used During the Analysis

• Kiwi Ears Allegro Mini.
• iFi GO bar Kensei.
• Hidizs SD2.
• Burson Audio Playmate 2.
• Aune X8 XVIII Magic DAC + EarMen ST-Amp.