IKKO Gems OH1S Dual Hybrid Drivers in-Ear Monitor Review

IKKO Gems OH1S Dual Hybrid Drivers in-Ear Monitor Review

Brand image

As a new brand (born in 2019), IKKO has been honored with Japan's VGP awards many times. Its exposure rate is not high, and there are few opportunities for an audition in physical stores, only occasionally "haunts" offline on the exhibitions. Everything can be changed. Not surprisingly, IKKO has begun to make efforts in the market and became very popular overseas. There is a big discount on the first new product. The review prototype is the new OH1s model of IKKO, as well as the upgrade wire CTU01 and ITM01 DAC.

Evaluation before measurement

  1. With its exquisite packaging, rich accessories, high appearance value, and strong texture, it is a sincere work at the price of $199.
  2. It has high-quality sound background, the tuning caters to young people, especially ACG tracks, with a good lasting appeal.
  3. It doesn't have a too picky front end, it was further improved after changing the line, and has great potential.


About packaging and details

The OH1s is beautifully packaged and the envelope is very quadratic. It can be seen that as a new brand, it has an idea that is completely different from that of traditional Hi-Fi manufacturers. It is "eye catching" starting from the packaging.



There is one more layer of the envelope under, printed with the appearance of the product.


After opening the cover, you can see the earphone body and a brooch with the image of a little cartoon fox, around which the design drawing and line draft of the product is printed.


Close-up of little fox brooch


The lower layer has an earplug cover, earphone cable and storage bag. There are many earplugs. It is worth noting that from the earplugs, we can see that the catheter of OH1s is oval rather than the usual cylinder.


The storage bag is made of PU with a thick stitching style.


The in-ear headphones use resin and aviation-grade aluminum alloy as the sound cavity to achieve the physical frequency division effect. It is made by inlay technology. It has a high appearance value and can withstand scrutiny. There are blue and purple options. In fact, the blue one is brighter, while the purple one is more low-key, since the metal part is frosted black.

Frosted metal and high permeability resin form a strong contrast between rough and fine. Therefore, it is quite "eye-catching" visually.



The original wire is made of 127um high-purity single crystal copper silver-plated magnetic core material, with a shielding layer and strong anti-interference. However, the official one still provides an upgraded wire.  



About upgrade wire and Headphone Amplifier

The upgraded wire is numbered CTU01 and is packaged independently, with 2.5mm, 3.5mm and 4.4mm plugs, as well as .78 pins and MMCX sockets, with a total of 6 options. The wire core is 8-strand 7-heart single crystal copper silver plating, the whole is thicker, and the wire is less easy to winding.


The Headphone Amplifier ITM01 is also a new product this year. There are iPhone and Android versions to choose from, and it supports game consoles such as switch (Note: ITM01 iPhone version is MFI certified, which is very rare, especially at the price of $59). ITM01 adopts ESS9298 DAC, which can decode DSD128 and PCM to 32bit/384kHz. The body is made of metal and resin, and the volume can be adjusted by pressing the keys on the body. ITM01also has three tuning modes: music, game and movie. Long press the middle circle key to switch.


The design of magnetic suction wire is very creative. It is very firm, but it is not particularly "firm". If there is accidental pulling, magnetic suction gets disconnected to avoid damaging the mobile phone charging port or earphone cable. In addition, the official wire upgrade package supports more devices after changing the wire.


About acoustics

OH1s is designed with deposited carbon nano dynamic coil and Knowles 33518 Unit Hybrid Driver. The deposited carbon nano dynamic coil unit is Knowles 33518. It is also equipped with diffusion structure, electronic frequency division, physical frequency division and other tuning measures, and the conduit also adopts a special elliptical structure. It can minimize the mutual interference between the sound generating units and make the sound more pure and transparent.


The officially marked frequency response range is 20-40kHz, which meets the Hi-Res standard. The impedance is 32 ohms and the sensitivity is 109dB/mW. It's not difficult to push on paper, but it also needs a good front end.


In short, in terms of acoustic structure, the design idea of OH1s is very strict. The frequency division and connection of the moving coil hybrid unit are also acoustically processed. It can be seen that it does not belong to earplugs that only sell beauty.


About sound

When it comes back to the voice, OH1s's voice is very targeted, because it is aimed at overseas markets from the beginning, while the brand image is aimed at young people. Therefore, the sound background is optimized for pop music and ACG. You can feel it from the beginning. The sound is light, the resolution is outstanding, the medium and high frequencies are smooth, the voice is delicate, the low frequencies are neat, and the atmosphere is strong. The ACG female voice is particularly excellent.

PS: the following are the offline listening feeling of the CTU01 upgrade of OH1s with 3.5mm plug.


"One Last Kiss", as an old fan of EVA, likes the final outcome (the perfect outcome) of the new theater version. The theme song presented by Hikaru Utada has been arranged for a double vinyl collection. In fact, this piece of music is not suitable as an audition, because the arrangement and soundtrack are relatively simple, and the requirements for resolution and extension at both ends are not high. However, the vocal part is still very exquisite under the restoration of OH1s. The sound is delicate and gentle, it has a trace of relaxation in deep feeling, and the artistic conception is very fit.


ACG is a compound name, not a single style. It can cover many types such as classical, jazz, pop, rock and electronics, and even cross-border or integrated works. Among them, the representatives of complex arrangements and diverse musical instruments must not bypass Hiroyuki Zeno, especially when the grand scene is burning and powerful. Taking the two theme songs sung by Aimer in "Mobile Suit Gundam Unicorn" as an example, the analytical power of OH1s is enough to support the complex arrangement. Aimer's timbre is also in place, high pitched, full of tension and purity. The soundtrack of the chorus can be clearly separated from the voice, and the sense of location and positioning are also accurate. The only regret is that the sound field is not wide. But my upgrade line is not the 4.4mm balance plug, because the opening of the sound field after the balance port will be improved to a certain extent. In these albums, the pure music part is also quite wonderful. The extremely low-frequency dive is deep enough and the drum sound is powerful. Together with other low-frequency instruments, it has a clear hierarchy, a strong sense of strength and quick emotional mobilization.


In fact, the tuning of OH1s seems to be fine-tuned and well-balanced as a whole, but also pays attention to emphasize the human voice, the dental has polished. However, it's very natural. It doesn't use high-frequency musical instruments. It has great analytical power. The restored timbre of instrumental music is correct. It's no problem to listen to classical or pure music. By the way, the extension of OH1s at both ends of extremely low frequency and extremely high frequency has been significantly improved after wire replacement. Personally, I recommend to directly replace the upgraded wire.



OH1s does not require specific front end. If you use a better music APP (Apple Music) with the official ITM01, it will perform well both in terms of resolution and dynamics, while if you have a Hi-Fi player, the OH1s will perform better after being upgraded.


As a affordable headset, OH1s also has an excellent match when listening to ACG tracks in a variety of auditions. It is more suitable for ACG than some more expensive earplugs. It is a very good "dessert" earphone.

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