Out Of Phase Conduction

Ratings

Pros

• It is a product with a lot of potential if mistakes are corrected.
• Good high end tuning, with moderate sparkle, but well extended.
• Three sets of silicone tips and a flexible cable.
• Comfort.

Cons

• Incoherent/deficient implementation of the bone conduction driver and capsule resonance, generating unrealistic, dual and out-of-phase bass.
• The resonant and elastic effect of the bone conduction driver persists well into the mids.
• Difference in sensitivity between the dynamic driver and the bone conduction driver. The bone conduction driver needs less energy to activate, generating an imbalance.
• No carrying bag/case.
• The effect of the resonance of the capsules is clearly felt with a simple click of the teeth or a small blow on the capsules.

Purchase Link

https://keephifi.com/collections/in-ear-earphones/products/kbear-kb02

Link to the Store

https://keephifi.com/

Introduction

KBEAR brand was founded in 2014 in Shenzhen China by a passionate young team, committed to the development of hi-fi products. The KB02 model is their latest creation, it is a hybrid model that mounts a dynamic driver plus a bone conduction driver. The capsule has been 3D printed in resin, while the polishing, painting and finishing is done manually for a premium finish. The dynamic driver diaphragm is beryllium plated and is located close to the mouthpiece to enhance mid and high frequencies. A high purity OFC conductor with a 2Pin 0.78mm connection interface is used for the cable. Due to the bone conduction, coupled with the vibration of the capsule, the low frequency effect is particularly prominent and powerful. The treble is smooth while there is a deep sense of space, excellent soundstage spaciousness and a strong, realistic sense of ambience.
Let’s see how closely the manufacturer’s information matches reality with the following review.

Specifications

• Driver Type: 10mm dynamic driver with beryllium plated diaphragm + bone conduction driver with 10mm elastic piece.
• Frequency Response: 20Hz-20kHz.
• Sensitivity: 108dB SPL/mW.
• Impedance: 40Ω.
• Jack connector: 3.5mm SE gold plated.
• Cable material: 6N OFC.
• Capsule Connection Type: 2Pin 0.78mm.
• Cable Length: 1.25m.
• Starting price: $39.99.
• Available in three colors: Crystal Violet, Misty Blue and Maple Brown.

Packaging

The KBEAR KB02s come in a relatively small box of 131x106x31mm dimensions. Its background color is dark and blends in with the color chosen for the capsules, while a realistic photo of the capsules is in the center of the box. The brand logo is in the upper left corner. The model name and description is also on the left side, a little below center. On the bottom are the model characteristics. On the back side are the product specifications in Chinese and English. Also on the back are the brand’s contact details, as well as the importers. At the bottom are the logos of the specifications that the product meets. Removing the outer carton shows a black box with the logo inscribed in the center in silver holographic ink. After lifting the lid you can see the capsules encased in dense black foam. Underneath is a black cardboard box with the logo repeated in the center. In it are the accessories. Underneath is a manual. The complete contents of the set are as follows:

• The two KB02 capsules.
• One black cable with 3.5mm gold plated SE plug and 2Pin 0.78mm connection.
• Three pairs of white silicone tips sizes SxMxL.
• Three pairs of black silicone tips sizes SxMxL.
• Three pairs of gray silicone tips and red core sizes SxMxL.
• User’s manual.

It does not come with a bag or carrying case. The cable made up of four coiled strands is not bad, despite the simplicity. It comes with three sets of silicone tips that are quite generic, but are different enough to find the best fit and sound with them.

Construction and Design

The capsules have been manufactured in 3D printed resin and finished by hand. They have dimensions of 20x23x17mm. The drawing of the external face is formed by a fluid pattern of mixed colored paint, but with a predominant base. In my case it is the Crystal Violet model. In the center of the face is the logo of the brand highlighted by silver pieces. The shape of the capsules is semi-custom, very rounded, with a triangular external shape with rounded corners. Everything that is not the external face is black resin, while the mouthpieces are silver metal. The connection interface is fully integrated into the body of the capsule and consists of a rectangular transparent plastic plate with smoothly rounded corners. The two holes are gold-plated. Next to this interface there is a hole. There is also another hole in the center of the inner face. This face has a slight protrusion at the end opposite the mouthpiece, although it is light, smooth and rounded. The center is slightly depressed while the nozzles emancipate quickly. The nozzles are metal and have two diameters. The lower is 5.3mm, while the crown is 6.5mm. The approximate length of the nozzle is 4mm. These nozzles are protected by a perforated metal plate.
The cable consists of four coiled strands coated with black PVC. The connector jacket is a black metal cylinder with 5 grooves near the cable outlet. The cable outlet is protected by a relatively elongated black cylindrical rubber sleeve. The 3.5mm SE connector is gold plated. The splitter piece is the same but a little more than half as long. The pin is an oval black plastic piece. It has one hole for each set of two wires for each channel. The fit is quite tight, so it’s hard to slip, but it holds the cable securely in place for the day. The sleeve for the 2Pin 0.78mm connectors are two metal cylinders similar to the splitter piece, but with a smaller diameter and only two slots. They have a white letter to indicate the channel, as well as a coating on the cable to give the over-ear shape.
The cable is simple, but of good quality, with a simple but effective finish. It is flexible and manageable, with low microphony. It is serious and sufficient.
The capsules are quite nice, with a medium size, though thick. I really like that flowing pattern of paint and micro glitter, and the silver logo formed by silver metallic plates gives it a more attractive look.

Adjustment and Ergonomics

The KB02 have a triangular shaped capsule with a semi-custom inner face, with a small protrusion at one end. The rounded resin construction gives it a very high lightness, as well as a soft touch and very pleasant to my ears. The protrusion is not very pronounced and hardly rubs, so the set integrates very well, pleasantly and is very suitable for long listening. The fit is effective, without rotation. The insertion is shallow, it could be medium if the ear canal is wide, but as the mouthpieces are thick it is not very possible. The fit is very occlusive with my home-made large foam-filled tips and an intense sound isolation sensation is generated. What happens is that the capsules, due to the bone conduction driver, has a resonant effect that is felt when you tap your fingernail on the outer face of the capsule or even when you click your teeth. This “bell effect” makes it not very suitable for external use such as for running or fast walking, as the movement can make this resonance counterproductive to the music. So I recommend its use for static or soft situations.

Sound

Profile

The KBEAR KB02 profile is a classic U or lowercase W profile that is very popular lately. I find nothing new in this type of profile and there are many references on the market that have a similar curve, even in a price range similar to this model. But the KB02s do present a difference that I have found in models with a price 10 times higher: it is the elastic bone conduction driver and its resonant capsule. The capsules of the KB02 resonate with the slightest impact on their casing. This causes the bass to generate a more pronounced reverberation, resulting in a more physical, volumetric and extended low end. On the other hand, it is also slower to recover, lingers longer in the environment and can be heavier, even fatiguing.
In addition, the middle and top of the KB02 is rounded, despite the slight excitation in the pinna gain zone. The treble is again restrained, starting with a slight recession, despite its good extension up to the air zone, where it decays clearly before reaching that point.
Because of their impedance level, the KBEAR KB02s require a certain level of power to match their direct rivals.

Bass

I recently reviewed the Apevoix Grit, a $220 IEMS that also has a bone conduction driver and resonant housing. Now I’m reviewing IEMS that are 5-6 times less and also have a bone conduction driver inside a resonant capsule. Are there similarities? Yes, but there are also clear differences. In the Grits the bone conduction driver and its resonance are perfectly aligned in tone and timbre with respect to the dynamic driver, that is why the bass response is enhanced and multiplied in many aspects. This is not the case with the KB02s. At low volume you can hear how the sound produced by the bone driver sounds one way and the dynamic driver another. At low volume the presence of the bone conduction driver is superior, it is something you notice with electronic music, when heavy bass kicks at the edge of the sub-bass come into play (around 30Hz-80Hz). The bone conduction driver and the resonance of the capsule generate a peak that shifts the actual timbre of the kick drums tone and they pulsate quite unrealistically. I have played many tracks and listened to a lot of music with the KB02s, even watched series, anime and TV. But when I started the review with my reference tracks is when I encountered this negative phenomenon. These powerful bass drums make the bone conduction driver pulsate in a way that is not coherent, nor realistic. The sound generated by the capsule is offset with respect to the sound generated by the dynamic driver, which is less audible. This generates a duality of sound that is more apparent at low volume and tends to tighten as soon as power is added. Although I would say that the sound of the dynamic driver eats into the sound generated by the bone driver. This effect is clearly generated by the capsule resonance because if both capsules are pressed finger tight to the ears this effect is diminished as the resonant effect of the capsules is minimized, controlled and limited. With this almost faulty peculiarity I could conclude the description of the lower zone. But, in reality, this is an effect that does not always occur, it is localized when running fast bass drums around 30Hz-80Hz. However, the very low frequency pure tone test is executed quite well and realistically. The lower tone is barely audible but feels deep and sensory. Admittedly, there is subtle ripple/oscillatory behavior, but it is slight and does not influence. It is clear that the very low frequency pure tone test is not negatively influenced by the bone conduction driver. With the other test of dirty, complex and unfiltered bass the result is better than expected. It seems that the KB02 behaves better at reproducing continuous bass lines, even if they are complex, than dry, fast and deep bass drums. So, the problem is relegated to “stopping the resonance/elasticity of the bone conduction driver in its tracks”. And that’s a real shame because it detracts from what could have been a thoroughly enjoyable low end, a bit slow, deep, deep, elastic, rubbery, powerful, punchy, pronounced, volumetric and resonant. On many occasions this is how it samples, but when I listen to electronic music with hard, dry drums, the result leaves something to be desired.

Mids

In the mid-range the male voices are presented in the middle distance, and may even lag behind the instrumentation based in the first half of the mids. The echoes of the bass resonance persist in the distance despite the fact that the music does not have much bass incidence. It is clear that the elasticity of the bass can intrude into the mids because of these echoes, even though the low end is tuned in a clear and steep descent towards the mids. But this I think is due to the bone conduction driver.
Despite this, both the timbre and tone of the midrange is correct, slightly warm, with relatively thick, smooth notes, but with that resonant base that is driven from the bottom or base of the sound.
The sound has a good level of transparency and clarity. It is not a luminous midrange, even at the peak of the pinna gain. It is clear that the female voices are more prominent and they escape the effect of the bone conduction driver, except for the counter highs. The female mid voices feel very well represented from start to finish, they don’t sound sharp, nor sibilant, but pleasant, balanced, even very resolving and fuller. The same goes for the electric guitars, which always come across as controlled even if on recordings they are edgy or sharp. The KB02 know how to tame them and make them sound more melodious, even powerful, but without losing a point of sparkle, within a level of clarity and transparency evident, but without being forced.

Treble

Initially, from what is shown in the chart, I thought the treble was going to be drawn very nuanced, as the high end starts with a clear rescission. But that maintained extension makes the treble very coherent, well extended and reproduced with a somewhat more muted sparkle for its measured energy level, but with a realistic and natural timbre and brightness. Even the thickness of the notes is favorable to the interests of the high end. In the air zone there is a typical clipping that does not detract from an upper range whose quality is better than I expected, both for its own presence and for harmonic support to the rest of the range.

Soundstage, Separation

What should be a deep, volumetric and physical scene is dismantled by the artifacts generated by the bone conduction driver when they occur. Otherwise, the scene appears that way, wide, with good laterality, expansive and deep. Even the headroom is good, also the layering of the bass lines, as long as there are no fast bass drums. The KB02s present a remarkable level of transparency and clarity. They do not have the most discernible background, but a good separation between elements is noticeable, as long as the elastic condition of the bone conduction driver does not come into play. At the macro detail level they are quite good, but they are not very resolving and the background micro detail is not discernible and is agglutinated by the whole. The positioning of the scene and its image is adequate, it has a good physical foundation, great volume, while it does not feel diffuse when working normally.

Comparisons

Tripowin x 0diBi Vivace

If more than a year ago my favourite IEMS under $30 were the 7Hz x Crinacle Zero 2, a few months ago the baton was picked up by the Tripowin x 0diBi Vivace. It was a duel of great audio reviewers sponsoring a low budget model and both won. I think 0diBi had it easier because they started from a known, successful base and only had to improve on that model. Clearly it was not an easy task, but I think it succeeded. And now you could say that any model around this price will have to fight against these kings. So the KB02 will have to face the Vivace. For now the KB02s are $10 more expensive, and what else do you get for that difference? Just an extra set of silicone tips and a sleeker, more attractive capsule. But the Vivace’s cable is thicker, with beefier metal parts. On the other hand, the capsule of the KB02 is thicker and slightly larger. Both models are very comfortable and the KB02s fit very well, as well as being soft. But the smaller size of the Vivace can be a blessing in the long run.
In terms of sound the profile of both is very similar. The difference lies in the elastic bone conduction driver and the resonant capsule. The KB02s need a bit more power to sound at the same sound pressure level.
From the very first moment the bass multiplying effect of the KB02s is fully noticeable, as well as the phase shift between the two drivers. The Vivace, on the other hand, have textbook bass. In the very low-frequency pure tone test, the differences are very low, I could even say that the KB02s are subtly superior, but only by a very small margin. They have a very slightly less ripple character, but nothing more. In the dirty, complex and unfiltered bass test, the better overall performance of the Vivace outperforms the competition. Overall, and without going into odious comparisons, the Vivace’s bass is very good, nothing to do with the KB02’s incoherent behaviour.
The KB02s recover quite a bit in the mids, but still drag that base that can be omnipresent and a bit overdone so that the central range can shine on its own. However, the Vivace are stellar in the midrange, with a presence of male voices with more flesh, more physicality, more body, fullness and closeness. They have a dense and full mid-range first part, but it is also very well balanced with the second part. There are hardly any faults in the middle range of the Vivace, where the level of coherence is very high, something that makes them enormously attractive and enjoyable. In comparison, with the KB02 one seems to be missing something. The Vivace are more expressive, closer, more explicit, sharper and better defined. The level of detail, the capacity for analysis and the level of information is also superior.
Perhaps the point where the KB02s can be on the same level as the Vivace is the treble. They are not as close as in the Vivace, where practically all the music sounds closer, the treble of the KB02 has a little more extension and a little more sparkle. The treble of the Vivace has more presence and is more concentrated in the first part. The extension of the KB02s makes them a little thinner, a little more distant, but with a more homogeneous and realistic brilliance.
The KB02s are more lateral and have a scene that expands almost backwards. This scene is more expansive and seems to emerge even from below, creating a more enveloping sensation. The Vivace are more common, more frontal and more normal in this respect. But they have more separation between notes, very good layering, a better level of detail, a sharper image and a clearer, more evident and coherent sound.

Conclusion

For much of my experience with the KBEAR KB02 I have been very excited about the potential of this model. But when it came down to it, as I went through the playlist I use for my reviews, I began to see the limitations, even the shortcomings. The implementation of the bone conduction driver in conjunction with the resonance of the capsule and the frequency response of the dynamic driver is not coherent. It even shows a phase shift in the tone produced by both drivers, generating sound artifacts that are not real, nor are they in the music. It is true that this effect occurs when playing electronic music, but even the resonant and elastic effect of the bone driver is felt well into the mid-range. Finding bass echoes in instrumental or vocal pieces is not the most appropriate thing to do. I insist, although it doesn’t always happen, when it does it sticks in my mind. However, when the artifacts don’t happen the KB02s show a potential that could place them among the best in the range for all other qualities. It is a pity.

Sources Used During the Analysis

• iFi GO bar Kensei.
• EPZ TP50.
• Tempotec V3.
• Burson Audio Playmate 2.
• Aune X8 XVIII Magic DAC + EarMen ST-Amp.