Stealth Sonics U2
Disclaimer
I would like to thank Stealth Sonics for providing the demo units for this tour and Jackpot77 of Audio Primate for organising the UK tour and letting me participate even though I escaped back to the continent last year. No incentive was given for a favourable review. This was originally posted as a single review, but adapted to fit the proper Head Gear sections, therefore certain sections will be the same as for the U4 (link) and U9 (link) reviews.
Links:
https://stealthsonics.com
https://www.facebook.com/stealthsonics/
Preamble
Stealth Sonics is a company based in Singapore and while a relatively new player in the IEM market, has had a decade or so experience in audiology/music technology in Southeast-Asia. I first came across them around the NAMM show in 2018 where Stealth Sonics launched their new IEMs. I enjoy occasionally browsing around to see what is new and what might peak my interest and Stealth Sonics certainly did the latter when I saw their universal IEMs. A bold design that made a statement: StealthSonics has Style. That is style, but then with a capital 'S', quite possibly it even needs to be italicised as Style. Whether or not it is your cup of tea is another matter altogether, but there is no denying that Stealth Sonics sets itself apart from the crowd. It is an extravert styling with bold colours and design elements, some of which are also functional (more on that later). For me, I am about as extraverted as a particularly agoraphobic hermit crab, so not quite my cup of tea although I do appreciate it when companies have their own unique Style.
It is not just the Style that sets Stealth Sonics apart. They have some really innovative ideas too. For one, their custom shells are coated with a proprietary lacquer that makes them extra hard. So hard that they can survive quite a large drop on a hard floor and that is not something I have seen very often. The universal shells too have some nifty design elements of which the Stealth Damping technology is the most noticeable because it looks like someone stuck a turbine engine to the faceplate. It is meant to help create a tight and clean bass response. The faceplates can however be removed to extend the bass, or replaced to make your universal Stealth Sonics IEMs look even more eye-catching.
Unboxing
The tour package contained the full retail packaging of the U4 to give an example of what you can expect when buying any of the three universal IEMs. So while I can only show the U4's unboxing, the experience should be the same for the U2 and U9 as well.
The universal Stealth Sonics come in a relatively big box covered by a sleeve with on the outside a picture of the IEMs and specifications. A bit more information can be found on the inside of the sleeve as well. The box itself has a carbon-like look and feel to it and opens up to display the universal IEMs in all their glory. Alongside can be found replacement faceplates. In the case of the U4 these are glossy blue, and I believe the U2's are red and the U9's black. Standard on all three are carbon-look faceplates. Below the IEMs is a generous size case, which contains a second cable with a mic, a bag with various ear tips (foam, silicone and double flange), adapters, an allen key for the faceplates, a microfiber cloth and a pouch. Overall a very healthy selection of accessories.
I believe that the regular cable is an SPC, although with all three IEMs it has a different colour: black for the U2, blue for the U4 and silver for the U9. The mic cable appears to be a pure copper one with clear insulation.
Build quality and fit
As I indicated earlier, the Stealth Sonics CIEMs have a uniquely strong build quality thanks to a special lacquer that strengthens the shells. The universal IEMs do not seem to be far off in that respect with a very durable feel to them, but it is a little deceptive because they are extremely lightweight. This low weight is purposely done to improve wearing comfort because Stealth Sonics aim at achieving long listening sessions (6-8 hours) without inducing signs of fatigue. Comfort is essential here and I do find that the low weight helps the IEMs to disappear while I wear them. The shell material below the faceplate also feels very soft and is very comfortable when wearing. The fit though was a little tricky for me to get right and I ended up using Final tips one size above my normal to get the best seal and most secure fit. I am not sure if I got the optimal fit, but time constraints meant that I could not spend too much time tip rolling. The reason it is a little tricky is because the stems are quite thick and short, so the fit becomes relatively shallow.
The included cable is quite a good one and comfortable to use, although the long ear guide did occasionally push and pull a bit more than I am used to because the cable did not settle around my ear. The cable's ear guides made the cable "float" (as it were) just above my ears because the shape of the bend is held very well, rather than something suppler that settles on the ear. Other than that it is certainly a quality stock cable that I think most people will be very happy with.
As mentioned, Stealth Sonics aim to achieve long, fatigue free listening sessions for their (C)IEMs and have fitted them with what they call a 'Klarity Valve'. This is a type of pressure relieve valve that helps minimise pressure build up during use. The vent of the valve can be seen on the inside of the shell, just alongside the 'L' and 'R' indicators of the monitors. I have had issues with pressure build up in the past and I find that the Stealth Sonics IEMs are about as comfortable as using IEMs with APEX/ADEL modules. I did not get any uncomfortable pressure build up and was quite happy to have the IEMs in my ears for longer periods of time.
Source
All listening was done with the Cowon Plenue 2 from the SE out.
U2 - The fun one
Presentation
The U2 have to my ears a mildly U-shaped signature with a solid bass that is balanced by a sparkly treble to add a bit of fun and musicality. The stage of the U2 is not the biggest, providing an intimate setting that is complimented by a somewhat holographic feel. It makes the U2 immersive and fun to listen to. While I would say the overall feel of the signature leans towards warmth, the U2 manage enough air to provide good separation and I did not notice much in the way of congestion, even with layered choral music. The background though is not the blackest I have come across. Perhaps I am spoiled, but the image lacks some crispness and definition. Not much of a problem though because the signature is musical enough that it will compel you to tap your feet nonetheless, making the U2 really good fun to listen to.
Bass
The bass of the U2 surprised me a little bit because it dug deep, was impactful and tight and yet I missed something I could not quite put my finger on. I suspected that this might have to do with the Stealth damping that Stealth Sonics incorporate in the faceplate and so I did a quick test without the faceplates, which immediately felt like the bass extended a bit better and resonated more naturally. I did not have enough time to do a thorough comparison, but it might be interesting to try out for anyone who enjoys an even deeper, lusher bass. I thought it worked quite well for the Rolling Stones, putting a bit more emphasis on the kick drum and bass guitar, but that might not always be what I aim for. With the faceplate on, the bass becomes tighter and more impactful, something that worked better for EDM. Although I will admit that my inner bass head always enjoys a deeper, lusher bass, even when it is strictly speaking not ideal. Of course you can have both in this case due to the U2's option to remove the faceplate or leave it on. It is however fiddly to do and I would prefer a simple switch (if it were at all possible with this particular system).
Mids
The mids are pretty decent. They are not the most natural sounding, but I will immediately state that as a mid-lover or 'mid-o-phile', I am very picky when it comes to my mids. The U2 sound far from artificial or thin, but lack some fullness and definition. Perhaps the U2 have a little too much emphasis on the upper-mids or lower treble, which is particularly noticeable through a lack of vocal density. In choral pieces such as Bach's Magnificat I find that male vocals lack some of the power they need to balance out the female vocals, but female vocals too lack some definition. Agnes Obel just does not sound like I expected based on the intimate setting the U2 produce. I might need to emphasise here that I do not have other IEMs in this price range for a comparison, so perhaps my bar is set to high and I am just a spoiled little brat because of the much more expensive, mid-centric IEMs I am used to.
Other than that the mids are nice and clear and even with classical music, which does not play to the U2's strength, I find that instrument tonality comes through very nicely. Move to proper fun music such as rock and the U2 perform really well.
Treble
The treble is a hint towards bright in order to provide the sparkle that compliments the fullness of the bass really well. It adds a little bite to guitar strings and indeed electric guitars sound pretty good. The sparkle and bite are not overly prominent and I don't think will give many issues to even the more treble sensitive souls among us. (Guilty as charged.) I always like to risk my life for my readers by testing for sibilance with a variety of soprano voices that are high enough to shatter my glasses even when I am using IEMs, and it was quite smooth with the likes of Elin Manahan Thomas.
The treble I feel is just about right to provide balance, a little bit of air and some clarity to the signature and it works really quite well.
Conclusions
Stealth Sonics have come up with a very nice trio of universal IEMs. The U2 have a signature that is engaging and fun, and I am disappointed I did not have the Final E5000 around anymore because it I suspect the U2 would give those a fair bit of competition. The U4 feel to me like great quality stage monitors that offer the complete package, a smooth and fatigue free signature combined with a very light weight and all the advantages of the Klarity Valve to make them as comfortable as it gets for long, very long listening sessions. The U9 offer clarity and detail at a very high level, while maintaining smoothness and accuracy in the reproduction of instruments. Where the U4 feel like stage monitors, the U9 might lean more towards studio monitors, although without foregoing musicality.
Stealth Sonics offer all their IEMs with a healthy selection of accessories and pack their IEMs with unique technology and styling to set them apart from the masses. At their respective price points the U2, U4 and U9 are interesting propositions, especially for those who prioritise practical aspects such as durability, comfort and a fatigue free listening experience. I feel Stealth Sonics have done an excellent job to create such a complete package and look forward to what they will do in the future.
Disclaimer
I would like to thank Stealth Sonics for providing the demo units for this tour and Jackpot77 of Audio Primate for organising the UK tour and letting me participate even though I escaped back to the continent last year. No incentive was given for a favourable review. This was originally posted as a single review, but adapted to fit the proper Head Gear sections, therefore certain sections will be the same as for the U4 (link) and U9 (link) reviews.
Links:
https://stealthsonics.com
https://www.facebook.com/stealthsonics/
Preamble
Stealth Sonics is a company based in Singapore and while a relatively new player in the IEM market, has had a decade or so experience in audiology/music technology in Southeast-Asia. I first came across them around the NAMM show in 2018 where Stealth Sonics launched their new IEMs. I enjoy occasionally browsing around to see what is new and what might peak my interest and Stealth Sonics certainly did the latter when I saw their universal IEMs. A bold design that made a statement: StealthSonics has Style. That is style, but then with a capital 'S', quite possibly it even needs to be italicised as Style. Whether or not it is your cup of tea is another matter altogether, but there is no denying that Stealth Sonics sets itself apart from the crowd. It is an extravert styling with bold colours and design elements, some of which are also functional (more on that later). For me, I am about as extraverted as a particularly agoraphobic hermit crab, so not quite my cup of tea although I do appreciate it when companies have their own unique Style.
It is not just the Style that sets Stealth Sonics apart. They have some really innovative ideas too. For one, their custom shells are coated with a proprietary lacquer that makes them extra hard. So hard that they can survive quite a large drop on a hard floor and that is not something I have seen very often. The universal shells too have some nifty design elements of which the Stealth Damping technology is the most noticeable because it looks like someone stuck a turbine engine to the faceplate. It is meant to help create a tight and clean bass response. The faceplates can however be removed to extend the bass, or replaced to make your universal Stealth Sonics IEMs look even more eye-catching.
Unboxing
The tour package contained the full retail packaging of the U4 to give an example of what you can expect when buying any of the three universal IEMs. So while I can only show the U4's unboxing, the experience should be the same for the U2 and U9 as well.
The universal Stealth Sonics come in a relatively big box covered by a sleeve with on the outside a picture of the IEMs and specifications. A bit more information can be found on the inside of the sleeve as well. The box itself has a carbon-like look and feel to it and opens up to display the universal IEMs in all their glory. Alongside can be found replacement faceplates. In the case of the U4 these are glossy blue, and I believe the U2's are red and the U9's black. Standard on all three are carbon-look faceplates. Below the IEMs is a generous size case, which contains a second cable with a mic, a bag with various ear tips (foam, silicone and double flange), adapters, an allen key for the faceplates, a microfiber cloth and a pouch. Overall a very healthy selection of accessories.
I believe that the regular cable is an SPC, although with all three IEMs it has a different colour: black for the U2, blue for the U4 and silver for the U9. The mic cable appears to be a pure copper one with clear insulation.
Build quality and fit
As I indicated earlier, the Stealth Sonics CIEMs have a uniquely strong build quality thanks to a special lacquer that strengthens the shells. The universal IEMs do not seem to be far off in that respect with a very durable feel to them, but it is a little deceptive because they are extremely lightweight. This low weight is purposely done to improve wearing comfort because Stealth Sonics aim at achieving long listening sessions (6-8 hours) without inducing signs of fatigue. Comfort is essential here and I do find that the low weight helps the IEMs to disappear while I wear them. The shell material below the faceplate also feels very soft and is very comfortable when wearing. The fit though was a little tricky for me to get right and I ended up using Final tips one size above my normal to get the best seal and most secure fit. I am not sure if I got the optimal fit, but time constraints meant that I could not spend too much time tip rolling. The reason it is a little tricky is because the stems are quite thick and short, so the fit becomes relatively shallow.
The included cable is quite a good one and comfortable to use, although the long ear guide did occasionally push and pull a bit more than I am used to because the cable did not settle around my ear. The cable's ear guides made the cable "float" (as it were) just above my ears because the shape of the bend is held very well, rather than something suppler that settles on the ear. Other than that it is certainly a quality stock cable that I think most people will be very happy with.
As mentioned, Stealth Sonics aim to achieve long, fatigue free listening sessions for their (C)IEMs and have fitted them with what they call a 'Klarity Valve'. This is a type of pressure relieve valve that helps minimise pressure build up during use. The vent of the valve can be seen on the inside of the shell, just alongside the 'L' and 'R' indicators of the monitors. I have had issues with pressure build up in the past and I find that the Stealth Sonics IEMs are about as comfortable as using IEMs with APEX/ADEL modules. I did not get any uncomfortable pressure build up and was quite happy to have the IEMs in my ears for longer periods of time.
Source
All listening was done with the Cowon Plenue 2 from the SE out.
U2 - The fun one
- Drivers: 1 x DD (Low/Mid), 1 x BA (High)
- Crossover: None
- Frequency response: 20Hz - 20kHz
- Sensitivity: 103dB at 1mW
- Impedance: 16 Ohms at 1kHz
- THD: <=1% at 1kHz
- Price: US$249
Presentation
The U2 have to my ears a mildly U-shaped signature with a solid bass that is balanced by a sparkly treble to add a bit of fun and musicality. The stage of the U2 is not the biggest, providing an intimate setting that is complimented by a somewhat holographic feel. It makes the U2 immersive and fun to listen to. While I would say the overall feel of the signature leans towards warmth, the U2 manage enough air to provide good separation and I did not notice much in the way of congestion, even with layered choral music. The background though is not the blackest I have come across. Perhaps I am spoiled, but the image lacks some crispness and definition. Not much of a problem though because the signature is musical enough that it will compel you to tap your feet nonetheless, making the U2 really good fun to listen to.
Bass
The bass of the U2 surprised me a little bit because it dug deep, was impactful and tight and yet I missed something I could not quite put my finger on. I suspected that this might have to do with the Stealth damping that Stealth Sonics incorporate in the faceplate and so I did a quick test without the faceplates, which immediately felt like the bass extended a bit better and resonated more naturally. I did not have enough time to do a thorough comparison, but it might be interesting to try out for anyone who enjoys an even deeper, lusher bass. I thought it worked quite well for the Rolling Stones, putting a bit more emphasis on the kick drum and bass guitar, but that might not always be what I aim for. With the faceplate on, the bass becomes tighter and more impactful, something that worked better for EDM. Although I will admit that my inner bass head always enjoys a deeper, lusher bass, even when it is strictly speaking not ideal. Of course you can have both in this case due to the U2's option to remove the faceplate or leave it on. It is however fiddly to do and I would prefer a simple switch (if it were at all possible with this particular system).
Mids
The mids are pretty decent. They are not the most natural sounding, but I will immediately state that as a mid-lover or 'mid-o-phile', I am very picky when it comes to my mids. The U2 sound far from artificial or thin, but lack some fullness and definition. Perhaps the U2 have a little too much emphasis on the upper-mids or lower treble, which is particularly noticeable through a lack of vocal density. In choral pieces such as Bach's Magnificat I find that male vocals lack some of the power they need to balance out the female vocals, but female vocals too lack some definition. Agnes Obel just does not sound like I expected based on the intimate setting the U2 produce. I might need to emphasise here that I do not have other IEMs in this price range for a comparison, so perhaps my bar is set to high and I am just a spoiled little brat because of the much more expensive, mid-centric IEMs I am used to.
Other than that the mids are nice and clear and even with classical music, which does not play to the U2's strength, I find that instrument tonality comes through very nicely. Move to proper fun music such as rock and the U2 perform really well.
Treble
The treble is a hint towards bright in order to provide the sparkle that compliments the fullness of the bass really well. It adds a little bite to guitar strings and indeed electric guitars sound pretty good. The sparkle and bite are not overly prominent and I don't think will give many issues to even the more treble sensitive souls among us. (Guilty as charged.) I always like to risk my life for my readers by testing for sibilance with a variety of soprano voices that are high enough to shatter my glasses even when I am using IEMs, and it was quite smooth with the likes of Elin Manahan Thomas.
The treble I feel is just about right to provide balance, a little bit of air and some clarity to the signature and it works really quite well.
Conclusions
Stealth Sonics have come up with a very nice trio of universal IEMs. The U2 have a signature that is engaging and fun, and I am disappointed I did not have the Final E5000 around anymore because it I suspect the U2 would give those a fair bit of competition. The U4 feel to me like great quality stage monitors that offer the complete package, a smooth and fatigue free signature combined with a very light weight and all the advantages of the Klarity Valve to make them as comfortable as it gets for long, very long listening sessions. The U9 offer clarity and detail at a very high level, while maintaining smoothness and accuracy in the reproduction of instruments. Where the U4 feel like stage monitors, the U9 might lean more towards studio monitors, although without foregoing musicality.
Stealth Sonics offer all their IEMs with a healthy selection of accessories and pack their IEMs with unique technology and styling to set them apart from the masses. At their respective price points the U2, U4 and U9 are interesting propositions, especially for those who prioritise practical aspects such as durability, comfort and a fatigue free listening experience. I feel Stealth Sonics have done an excellent job to create such a complete package and look forward to what they will do in the future.
