KZ S2

General Information

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Bluetooth is SBC for Android 9.

Latest reviews

Pros: 1. Very nice and clean vocal range
2. Rather neat and clean looking
3. Very comfortable even over prolong use due to its lightweight
4. Easy to connect/pair with devices
Cons: 1. No APTX (Kind of unfriendly to android based products including DAPs)
2. Battery life between 3-4hrs sound reasonable but charging time is long. Took me around 2hr to charge up from roughly 20% to full?
3. Lacking bass and treble (Initial listening)
Fresh out of the box
The initial listening was a "super" disappointing one for myself. Upon pairing, I excitedly opened up my Hiby app to listen to a few songs. Although I was expecting to receive a rather "flat" signature earpieces like what most of the reviewers before me reviewed, I would not agree with their statement. What I find myself in is a BT earpiece that sounded very lacking in both bass and treble. Virtually it sounded as if the instruments were a few meters behind the singer. You clearly hear the singing but the instruments just felt as if it was wrongly tuned or pretty much half missing. I use the term "half-missing" as a mean to illustrate that you would know it is there when interludes/breaks come in.

After making sure it isn't the EQ preset that ruined that earpiece (I did not have any EQ settings on on my phone), I fool around with the presets and realised the "vocal" preset is super cool on the earpiece. This preset further suppressed the sub-bass and treble revealing only the vocals. That momment I was like "WOW!!! This clarity of the mids and vocals". The experience is like someone trying to sing right beside your ears, so tender and intimate...

Using for around 2 hours, the treble and bass starts to come out more prominently but I would still call it lacking on both ends with my EQ off. But it definitely sounded much much better.

Almost a week down the road
I continued to use it for about 3 hours daily to play game, listen to youtube music etc. What I find myself in is the super flat sound signature that a lot of people have been reviewing about. Then you would be wondering is that good? In my humble opinion, although it does sound much better and my instruments are starting to come in after they are late for a week, I'm still more inclined to using it as a pure "vocal" earpiece for listening to music with emphasis over vocal region.

I tried fooling around with the presets of EQ as well as manually tuning the EQ, but all these efforts, some did further improve my experience with the earpiece. But I'm gonna say, nahhhhhh my vocal EQ still sounded the best.

Breakdown (intial vs a week down)
Sub-bass: 4/10, 5.5/10
Bass: 5/10, 7/10
Low mids: 9.5/10, 9/10
Centre mids: 9/10, 9/10
High mids: 9/10, 8.5/10
Lower treble: 6/10, 6.5/10
Higher treble: 5/10, 6/10

You might be wondering why the mids score dropped after a week, the reason behind it is the fact that as the bass and treble comes in, the impact of pure,clean vocals is slightly polluted/not as significant as before due to some bleeding over the trasitioning frequencies. One thing I forgot to mention above is that high vocals range going into the lower treble, I did not hear sibilance so I gave it slightly higher score for low treble.

Take note that the score is given based on comparison over the earpiece's different ranges itself not as generic comparison/ "enjoy" level. Let me know if you prefer that, will edit in here as well...

Conclusion
Is it worth the money? Yes and No... I got it during the indiegogo campaign and felt that is worth the price, does it peform better than competition at that price range, a very certain YES! But would I buy it at the RRP? The answer is 75% chance I won't unless the intended purpose is for a comfortable bt earpiece for general usage such as calls, watching video and playing games or purely for listening to audiophilic vocal pieces.

If you are a bass head or a fan of KZ typical V shaped signature, this is not the earpiece you are looking for.
On the other hand, if you are the kind that prefer your music to be very flat/ balanced throughout the spectrum, I would highly recommend this to you.

Additional comments
Down here there are many people that might disagree with me over the fact of burning in earpieces. In my honest opinion, I personally felt it unnecessary for BA earpieces. But when it comes to any earpiece that have a DD including hybrids, my experience tells me that it is essential. I also believe that it is what often caused the "initial" experience to be less enjoyable than something a week or two down the road and something you have used for months.

I'm not sure if it is true, but I was told a DD works pretty much like a speaker driver and it takes time and usage for the diaphragm to loosen and produce its' intended sound (Actually that would explain why it only gets better).
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Pros: True TWS form factor, good battery life, respectable sound quality, improved connectivity, IPx-5
Cons: no LDAC or AptX support, odd location of charge port and LED battery indicator, noisy mic, limited kit


disclaimer: The KZ S2 has been much anticipated and having enjoyed the E10, I was interested in seeing how this new model would fare. I was provided the S2 by LinSoul Audio for purposes of this review. The S2 is a bit different from most KZ models as it was crowd-funded and to some degree crowd-sourced as much discussion has gone into what the S2 should be and the specs have shifted considerably since the early discussion with a different bluetooth chipset as well as other changes, so I am interested to see how this product will perform. If you have an interest in the KZ S2, visit Linsoul Audio or their Amazon Store.

Unboxing / Packaging:

The S2 ships in a white lift-top box with the line drawing on the front and the KZ address on the rear, details of the drivers etc are not on the box as is typical for KZ. Lifting the cover reveals the case in a plastic tray, under the tray is a short (6 inch) USB type-A to type-C cable, a warranty card, the user manual, and a single spare set of tips. Earpieces are in the case and do have a set of tips installed so you get two medium sized sets of tips in the package. This is probably the single biggest complaint here as for $29 I don’t expect miracles but a full set of tips to allow for better fitment is a must.



Build/Fit:

The shell on the S2 is a 4 part design made mostly of black resin with a brass nozzle. The outer faceplate is made of two parts: the shell itself and a large central button with the KZ logo. A large slot vent is cut in the rear face of the faceplate near the upper edge. The LED is visible through this vent so we have to assume it provides an ingress for sweat although the S2 is listed as IPX-5 water resistant. A second small vent exists below the nozzle on the inner shell. The inner shell is the semi-custom ergonomic shape that has become the norm in recent years. The joint between the faceplate and the inner shell is easily visible and felt readily with a fingernail but is uniform with no glue or slop present. The nozzle exits the body at nearly its lowest point with an acute forward rake for fairly deep insertion. I found the S2 fairly comfortable for longer listening sessions but did have to do some tip-rolling to find a slightly larger tip than those provided to get the seal I wanted. Even with those larger tips, isolation is only average.







Internals:

The heart of the S2 is a 7mm dynamic driver coupled with a KZ made 30095 balanced armature driver. I mention the maker as increasingly the numbers alone are becoming generics and several makers now produce a 30095 series driver. The Dynamic driver is listed a dual magnet, with a composite diaphragm but no further details were available at the time of this review. Connectivity is hadnled by the Realtek 8763 chipset and offers bluetooth 5.0 support with SBC and AAC connectivity, but lacks the Apt-X HD and LDAC some had hoped for. Per KZ, this was done to improve compatibility as AAC was more readily available on a broader spectrum of devices and battery life as it was a bit more efficient than the Qualcomm alternatives.

Controls:

The touch controls are better on the S2 than some recent models with a single touch being used for play/pause. dual tap on left is back, dual tap on right is forward, triple tap is mode switch between high performance and standard modes, and press-and hold is turn off/on/pair. Controls react quickly which is also appreciated as some other touch models I have tested left me wondering if I had hit the right button by the time they reacted.

Connectivity:

Early discussion of the S2 had included a Qualcomm chipset that would have included Apt-X HD support and possibly LDAC but at some point in the prototyping it was decided to move to the Realtek chip and focus on AAC protocol support instead. This is probably due to the fact that the S2 is positioned as a direct competitor to Apple’s products as can be seen in KZ’s marketing materials (shown below). I did find the S2 worked well when connected to devices that supported AAC, but suffered some with devices like the Hidizs DAPs that support LDAC, and AptX protocols but not AAC. Distance between source and earpiece was roughly 10 meters before break up started and a single layer of drywall often did not defeat the signal. Longer distances or heavier walls did fairly easily defeat the signal. I did appreciate the low latency option (triple tap to engage) as it did a good job of reacting instantly to commands and keeping video in sync with audio on my devices.


Case/Battery:

The case is fairly typical of TWS offierings of late with plastic all the way around. The upsides are it does have a proper metal hinge and a magnetic closure on the lid. A single button on the reverse is used as a battery indicator prompt, but the LED indicator that displays charge status is unfortunately on the inside of the case. This is a bit odd in that the button is most easily seen by turning the case to orient the rear toward you, but then the LED is blocked by the lid of the case unless you change orientation of the case to view it. When the button is pressed, the LED will display Red if the case is between 0-30%, yellow for 30-70%, and Green if over 70%. The button does not work when charging the case as the light stays on solid red while charging and turns green on full charge. Another odd feature of the case is the USB type-C port which resides on the bottom of the case for charging. You cannot set the case on its base and charge it at the same time, this again seems like whoever designed this cared very little about ergonomics.

The case sports a 500mAh Li cell battery that measured 429mAh in my tests and each earpiece has an internal 50mAh battery. I didn’t attempt to test these as my equipment’s minimum discharge rate is high enough I was afraid of damaging the tiny cells. KZ lists the S2 as having up to 4 hours of listening time or 2 hours of talk time if the microphone is engaged. I found both of those numbers believable but perhaps slightly ambitious with my listening times being closer to 3 hours than 4 when using the S2 at normal listening volumes (82dB). Recharging the earpieces takes roughly 2 hours from drained to full charge. The case is able to charge the four times before the case has little enough remaining capacity that a full charge cant be delivered. A fifth partial charge may be possible depending on depth of discharge before the earpieces were returned to the case. Using the phone does reduce the battery life to closer to 2 hours and for my use it was slightly under that. A low battery vocalization will be heard in the earpieces as it approaches cut-off. I found that usually I started getting cut-outs about this same time.



Call Quality:

Ok, lets just be honest up front, if you were planning on using these for office meetings and important business calls, you may be better served by something else. It picks up a fair amount of surrounding noise and even in quiet environments there is a background hiss produced by the mic. Voices are clear to the listener wearing the S2, and speech is easy to hear for those on the other end of the call but quite often they spoke of hearing a hiss or a noisy background. I think, for many, these will be used for music listening with only the occasional call thrown at them and I think this is the best use case as for call quality other models offer more in the same price space. The Dudios shuttle that I reviewed was a better in ear for calls, but won’t rival the S2 in overall sound.

Sound:



Bass:

Sub-bass has good extension, is elevated with a center around 80Hz and a mild roll-off that only becomes notable below the mid-30s. The S2 is able to deliver good rumble when called upon without getting really lose or sloppy. Mid-bass drops throughout its range and is a bit less pronounced than the sub-bass but retains good definition and presence in the mix giving the S2 no lack of slam at the low end. I think KZ has done a good job with the speed of the 7mm dynamic here as it quick attack and just slightly slower decay which give the sound good texture and a natural tonality that is lacking in a lot of TWS. I applaud KZ for a low-end with both good definition and some slam and rumble when called upon.

Mids:

The lower-mids continue the decline from the sub-bass peak and while not emphasized like the sub-bass and treble, overall the mids still have good presence and don’t sound overly recessed. This step back does mean vocals are on the same plane with guitars and other instrumentation and don’t cut through the mix quite as well as one would like at times, but it also means they don’t sound artificially elevated either. Upper mids climb a bit forward and female vocals tend to be a bit in front of their male counterparts as a result. String timbre is not quite realistic, but one must remember the price point here as that is a lofty expectation. Midrange detail is good but the tonality is a touch bright and tracks that tend toward sibilance will show that and be a bit strident at times. This is not to say the mids have that bite if the track doesn’t take it that direction anyway, but it does little to attenuate that either.


Treble:

Lower treble climbs fairly rapidly, continuing what the upper-mids started. This pushes the lower treble to the foreground and gives the S2 good energy and some extra life rather than sounding a bit dulled. It does seem that KZ has continued to work on tuning the 30095 (either internally or by crossover design) as this iteration is not as splashy and strident as several earlier models. The true treble retains the same energy level as the lower up through about 7.5kHz which gives snare rattle good realism and highhats just a touch of metallic sound but overall very good at the price point. Final roll-0ff is somewhere above 13kHz which is quite good regardless of price but exceptional at the asking price here. Detail is good throughout the treble with good air and sparkle at the top. The only caution here is the treble is still a bit hot and sparkle can and does become sizzle occasionally.


Soundstage / Imaging:

The S2 has good stage size with slightly better width than depth and does even muster some height in the mix. Seating the orchestra was fairly straight forward although the S2 has somewhat limited instrument separation when compared to the E10 or Zs10pro but still quite good when compared to other TWS models I have tried Thus far. Movement around stage is quite good but somehow never quite feels that it reaches dead center in front, but otherwise feels fairly precise. Layering is fairly good for TWS but again fairly limited in the overall. Compression becomes fairly evident as the volume gets louder and the tracks get busier so keep that in mind, the S2 is best at moderate volumes.


Thoughts / Conclusion:

There has been a race on to create a budget earpod killer. Most makers either have released or have planned some form of TWS product targeting everything from the casual listener, to the office user, to the gym rat. KZ through their hat in the ring with the E10 but quickly found that its form factor of earhooks was a negative for many, and its connectivity wasn’t as good as many had hoped. This go around, they backed off the sound quality a bit (The E10 was basically A Zs10 Pro sonically) and instead focused on giving the people what they had asked for. The S2 is IPX-5 rated, is a true TWS with no earhooks or appendages, has good battery life, and better connectivity than its predecessor. Sonically, it is a V shape with good lively sound for popular genres and enough call quality to be good paired to a phone. While the treble is still a bit forward, it is more refined than earlier efforts, and can be tuned back a bit with EQ for the more sensitive folks. The S2 may just be the best option available for those looking for a budget TWS. Yep, it beats the Sabbat, the Dudios, and Simgot models I have tried, and even its larger sibling the E10 in most respects. To get better than the S2, you’ll have to spend at least twice as much based on my experience to date. While I still wish for and LDAC model, this thing is well worth considering even without it.
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Pros: Type-C USB – Highly ergonomic, comfortable, and stable shell design – Crisp, clean v-shaped sound – Low latency “performance” mode actually works well
Cons: Tip selection (or lack thereof) - Background hiss – Battery life isn't amazing – Micro-drops when connected to older sources – Not a fan of touch controls
Greetings,

If you've been following my content over the years you'll know that Knowledge Zenith (KZ) has played a big part in my journey from total newb to whatever I am now. I was around for their early models like the ANV, Micro Ring, and R3, and saw them finally break into the mainstream to set things alight with affordable hybrid iems like the ZST and ZS5.

You also might have noticed my lack of coverage of their most recent generation of earphones as a result. The reason being? The lack of forward momentum just wasn't there and everything ended up sounding like an iteration, albeit iterations with improvements (some vast), of that original ZST sound. When I was invited to check out the S2 I had to accept. My only experience with Bluetooth gear from KZ was limited to their original 2-pin cable. While I got lucky in that mine still works perfectly and usually spends it's time powering the equally aged Rose Mojito earbuds, KZ's record with wireless products has been a little spotty. I was curious to see if they got it right with the S2, and for the most part, the answer is yes.

Let's take a look at the new true wireless earphone from KZ, and see why this one is a solid budget friendly option in what has quickly become a very crowded market.

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What I Hear If you like the KZ “house sound” you should be right at home with the S2 since it brings nothing overly new to the table. That's not a bad thing since I quite like the v-shaped signature Knowledge Zenith has been touting since they started releasing hybrids.

Treble is well-extended and has a distinct brilliance region focus to my ears. This gives the presentation a bright, airy, shimmery feel that is fun and vibrant, if not potentially fatiguing. Treble sensitive listeners need not apply. In the past I've found KZ's with this bias to sound somewhat loose and splashy, so I was pleasantly surprised to find notes tight and well controlled with a reasonably realistic attack and decay. Detail is good, if not slightly exaggerated given the shift in emphasis to the upper treble regions. While still a bit too bright, I'm glad KZ dialed in and cleaned up the output of their 30095 armature for this application. Overall treble quality is quite good for an inexpensive hybrid, and a wireless one at that.

The midrange is recessed and plays second fiddle to the treble and bass regions. While vocals are less prominent than I'd like and somewhat overshadowed by frequencies at the extremities, they still remain clear and coherent with good tonality. Timbre is somewhat light and bright with a hint of plasticity to it, especially noticeable when a drummer taps their stick on the edge of the drum, but not so far off that I found it distracting in any way. Sibilance is present but not extreme and is handled much better than one of KZ's more popular recent models, the ZSN Pro. In general, I found the mids here to be satisfying, I just wish they were either pushed forward a bit more or the other frequencies were dialed back a bit to change the perceived recession.

The bass performance out of this earphone should satisfy a lot of listeners. Extension is quite good with the S2 able to delve out some decent visceral feedback on deep, rumbly notes. Midbass is quick and provides good punch, something that seems to be common to the dual-magnet design KZ has gone with this time around. Notes feel textured and detailed as evident running the S2 with some grimy tracks from Tobacco and The Prodigy, something that can often be an issue with wireless sets. Speed isn't an issue either with quick transitions being handled with tact and grace. Bass isn't often an area where KZ falters, and the performance here is right in line with expectations. Good stuff.

For a truly wireless earphone, I was quite impressed with the sound stage. The S2 feels quite expansive with a wide and deep stage that has sounds transitioning from channel-to-channel quite accurately. Testing it out with gaming I found sounds dead centre to feel a little off, but as soon as they moved to either side the movement was smooth and reliable. I actually wouldn't be entirely opposed to using these for some light, competitive gaming. Laying and separation are also better than average for a TWS, only faltering at high volumes where the staging begins to compress and sounds start to meld into each other and lose definition. I never listen at those volumes though, so while it was never an issue for me beyond the few minute I cranked the volume that loud, you might find it intrusive.

Overall I am quite happy with the sound coming out of the S2. While nothing new and special, this v-shaped signature is smooth and detailed with good staging qualities and deep bass that can really carry a track. It definitely sounds best when paired with the artificial elements inherent to electronic music and most modern pop, but it can still provide a good experience with rock and other genres. It also performs best at moderate to high volumes to avoid hiss which is audible at low volumes, and stage compression which occurs at very high volumes.

Compared To A Peer

SoundPeats Truefree+ (~35 USD): While both have a v-shaped signature, the TrueFree+ is less extreme. The S2's upper treble is more prominent giving it a more shimmery presentation and airier feel. Notes are also more controlled with overall a much higher quality presentation. The Truefree+ sounds somewhat rough and unrefined in comparison. Overall detail and clarity are in the S2's park, despite the exaggerated treble that makes then feel even more detailed than they already are. The Truefree+'s midrange is thicker, more forward, and more natural, but lacks the clarity of the S2. I still prefer the Truefree's presentation regardless since it feels more coherent and better integrated into the overall signature. Bass between the two is quite comparable with similar levels of extension and texturing. The S2's low end is a bit smoother and comes across a little more organic, but doesn't feel quite a quick. Sound stage is where the S2 is much superior providing a significantly wider listening experience. I was quite surprised as this since the Truefree+ was already quite good for a TWS. Even so, the Truefree+ obviously lacks the width and the S2's ability to toss sounds way off into the distance. It also has a more intimate default position for vocalists which tends to have the effect of pulling the stage in further. Imaging I found tighter and more accurate on the Truefree+, but layering and separation in the S2's camp thanks to all that space the music c an play around in. While there are aspects of the Truefree+ I appreciate more, like the mids, I found the S2's sound stage and treble refinement to provide the better listen. That said, the Truefree+ has a cleaner background in places where there is noticeable hiss through the S2, and might be better is you often listen in quiet areas at low volumes.

In terms of comfort and usability, I'm split. The S2 is more ergonomic and provides a more stable fit in my experience, but the Truefree+ has a more common bean shape that has been shown to provide a more universal fit among various ear types. Despite the S2's more form fitting shape, it also doesn't passively isolate quite as well. The Truefree+ also has physical controls vs. the S2's touch-based controls. No surprise, I much prefer the physical controls which are very difficult to activate by accident. Comfort when using them is sacrificed slightly, but it's worth it to avoid the finicky nature of the S2's interface.

Both of these earphones have the same 3.5-4 hours rated battery life. However, battery performance out of the Truefree+ well exceeded my expectations back when I first tested it giving me over 5 hours of listening time. The S2 has been fairly consistent in giving me around 3 hours and 45 minutes of listening time. The Truefree+ has also provided a more stable wireless connection. The S2 suffers from occasional stuttering. At times it almost feels like the two earpieces are quickly re-syncing since volume will drop in the right earpiece, then pick right back up. All of these imperfections pass by in a fraction of a second and honestly do little to hinder the listening experience, but since they're not really present at all on the Truefree+, well, you know which gives the superior performance.

Overall I like the sound of the S2 more, it looks nicer, and fits my ears better, but the Truefree+'s battery life and connection quality are superior. The physical controls are also much nicer to interact with in my opinion. Whatever it is you value most, pick the one that offers that.

Astrotec S80 (89.00 USD): While both earphones have a v-shaped signature, the single beryllium-coated divers of the S80s aren't as skewed and have a warmer, thicker feel top to bottom. Where the S2 skewed balanced towards the upper treble the S80 rolls off and focuses on lower treble. Overall detail is similar but the S2 feels more nuanced on first glance thanks to it's leaner more spacious note presentation. The midrange is dominated by the S80 which is more forward and audible with a more accurate timbre and tone. It does a better job representing a wide variety of vocal styles and artists. Bass on the S80 is a bit more tame compared to the S2 with less low end rumble to it. It is also a bit smoother and less textured with a slower, softer attack. That more relaxed presentation gives note more body though, and things like a slow, chugging guitar riff hit in a way the S2 can't match. The S2's sound stage is notably wider and deeper with more space between notes. Imaging performance is similar off-centre with the S80 showing none of the on centre quirks of the S2, though layering and instrument separation are mostly on par.

When it comes to comfort and usability, the S2 wins hands down. I find the S80's shells somewhat awkward and unstable to wear due to the stubby shape and short nozzle, particularly with the stock tips. Comfortable though. The large touch pad also means I pause my music by accident constantly. That happens with the S2, but not to the same extent. The S2's controls are also much more in line with the rest of the industry using more traditional actions to perform functions. The S80 can control volume though, so while its functions are less intuitive to access, it has more of them.

Battery life out of the S80 is quite a bit better. 6 hours isn't unattainable and you get it from the same 2 hour charge time. The case also adds an extra 25 hours of play time vs. the 14 of the S2's case. When it comes to connection stability, the S80 is more reliable and less prone to the occasional hiccup. The S2 managed to best the S80 with its impressive range though.

Overall I prefer the more natural sound, less skewed sound of the S80. However, the S2's ergonomics, more intuitive control scheme, and seriously good range have me leaning in it's favour simply because it is nicer to wear and use, even if connection stability isn't as reliable. Oh yeah, it also lacks the clean background of the S80, so there's that too.

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Tech Inside Depending on what you are connected to, the S2's connection is either quite good or somewhat flaky. Stuttering was fairly common when connected to my ASUS FX53V laptop, especially in the low latency high performance mode. Things were much more stable connected to my various smartphones, like the LG G5, G6, and Q70, regardless of the performance mode. The first few runs though the battery I found that every once in a while the right earpiece would briefly drop in volume, then raise back up to match the left. It felt almost like the two sides were resyncing. This issue hasn't cropped up during the last two complete charges so I'm not overly concerned. Despite the occasional hiccups when paired to my laptop, the S2 has been fairly consistent and never fully disconnected without being prompted to do so. The two sides have also never had any issues connecting to each other. Range was also excellent. Regardless of where the source device was, I could walk around my apartment and the connection would remain strong and clear with no hesitating (beyond the occasional stutters mentioned earlier), regardless of how many walls and rooms were in the way. Pretty impressive for a budget TWS.

Latency is another positive. Even in the low latency mode I find the S2 satisfactory for watching videos. Connected to my LG Q70 there was a very mild desync with voices, but nothing unwatchable. Tossing the S2 into the performance mode lowered latency to the point where any delays weren't audible/visible to me. Connected to my laptop the desync was more prominent and while switching to the high performance mode fixed this, it introduced connection instability. I guess my advice it to ensure you're using the S2 paired when paired to more up-to-date products for the best experience.

Battery life out of the S2 is fine, but nothing spectacular. It is rated for 3.5 to 4 hours. Connected to my LG Q70, I've been seeing around 3 hours and 45 minutes on average, usually at or below 1/3 volume. The S2 gets very loud very quickly, and I listen very quietly for the most part.

In The Ear With the S2, KZ has done a wonderful job translating their recent designs into the TWS world. The shells are very similar in size and shape to the ZS10 Pro in profile, with added depth to enable the necessary electronics to fit inside. While the inner portion of the ZS10 Pro is smooth and featureless, the S2 takes a similar approach to the ZSR with custom-like protrusions that help lock the S2 into your outer ear. This goes a long way towards keeping stable during movement. This design feature is very important in my opinion, because the S2 is fully wireless and does not utilize ear hooks or any other feature with a similar function to keep the product in place. This lightweight, form fitting design has been very comfortable in my time with the S2, and I have no problems wearing it for the entire duration of it's battery life of around 3.5 to 4 hours. I've been averaging around 3 hours and 45 minutes when connected to my LG Q70 with the sound quality preference enabled, and the S2 on its regular latency standard mode. Not amazing battery life, but quite satisfactory for most use cases.

When it comes to build quality, the S2 doesn't look or feel like anything special, but it has proven to be durable. I found out the hard way when the left earpiece slipped out of my fingers and over our balcony on the fourth floor, ricocheting off a second floor balcony on the way down. Evidence of the trip was limited to a couple small scuffs. While tough as nails, the plastic used for the ear pieces has that distinct washed out look and oily feel you commonly get with inexpensive, slippery, glossy plastics. The logo on the face plate is a matte texture, something that would have been nice if carried over to the entire earphone. Regardless, fit and finish is fine, though my set did have a number of scratches on the rear of the right earpiece out of the box. I assume that since this is an early production unit, such mild blemishes will not be an issue on the the eventual retail models. After all, it is still going through an Indigogo funding campaign. Also note that the S2 is rated for IPX5 water resistance. I haven't had the chance to test it yet, but those looking to use these while working out shouldn't have to worry about sweat ruining them.

When it comes to the case, I'm quite pleased. First off, the matte plastics used are nothing special and feel about as basic as it gets, but they managed to keep it relatively compact and slender enough to fit comfortably in most pockets. While the placement of the USB port on the bottom (???) is an odd choice, I think this is appropriately countered by a proper metal hinge, the lack of which I've expressed concern about on numerous models from other brands and at much higher costs. This will certainly give the S2's case a welcome durability advantage over much of the competition. Some other nice touches are the strong magnets that keep the lid shut, as well as hold the earphones in place and the contacts lined up when dropped into their charge ports. Lastly, there is a button on the back that when pressed lights up an LED under the lid advising the approximate charge level of the case.
  • Red – 0-30%
  • Yellow – 31-70%
  • Green – 71-100%
When charging the light remains a solid red, and when fully charged switches to green

Using the device is mostly a solid experience, though as is always the case I find touch controls on such compact devices somewhat finicky. The logo on the face plate is the touch point and quite sensitive. As such the various control options are response, pending you tap the right spot. I found it helpful to grip the tapered front of the earpiece with your thumb and middle finger, leaving your index finger to tap accurately. While you can't control volume, other common functions are present like answering and hanging up calls, and playing/pausing and skipping through music tracks. Oddly, I found the triple press needed to activate the high performance mode the most reliable function. If any of the functions were to be changed, I request the single tap to hang up phone calls. I routinely found myself hanging up on my callers by accident. A single long press would resolve this. For those calls I was able to complete, the call quality was decent. Those on the other end found my voice clear, if not a little quiet. The S2's active noise cancelling feature during phone calls seems to work fairly well.

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In The Box The S2 arrives in a bright white lift top box similar in style to other similar products in the same price range. On the lid is an image of the earpieces in a wireframe style art form along with their new brand logo and model name. On the left and right sides is one of KZ's original logos. As a long time fan of the brand, I really appreciate this nod to their history. Flip the box over and you find numerous contact and location options for the brand, as well as an important notice.

“In order to ensure the service life and safety of the equipment, do not use fast charger for charging.”

Lifting off the lid you find the charge case tightly held within a stiff, plastic tray. Lifting the tray out reveals the included accessories, a warranty card, and a surprisingly well-written instruction manual. In all you get:
  • S2 earphones
  • Charge care
  • Silicone ear tips (m x2)
  • USB Type C charge cable
In all a very basic unboxing experience. While the included tips are very high quality and extremely comfortable, you only get two pairs and only in one size (not small and medium which I originally thought) which will be an issue for some. Hopefully KZ decides to toss in some of their community named “Starline” tips, or at least multiple sizes of the existing tips, once the S2 is done its Indiegogo campaign and is up for regular retail sale.

Final Thoughts Taken as a complete product, the S2 is a very solid true wireless earphone. My favourite aspect is that KZ managed to cram all the electronics and drivers into a familiar and comfortable design, without much compromise beyond the shell being a little thicker than it would otherwise need to be. If you like the comfort that this style of low profile shell provides and is used by brands such as KZ, FiiO, TFZ, Dunu, and various others, you will feel right at home with the S2.

The sound quality is also quite enjoyable with good end-to-end extension and plenty of detail, pending you enjoy a v-shaped signature and vibrant upper treble. There is some background hiss that requires moderate volumes to cover up, but after a couple minutes I always forgot it was there and it did little to ruin my enjoyment of my music. This isn't the sort of earphone you hook up to your pricey hi-fi setup and analyze the hell out of after all.

Connection stability is decent with minor hiccups here and there, but it's backed by a very strong hold that remains that way over good distances, even with obstacles in the way. I can deal with blips as long as the connection never actually drops, and it hasn't yet. Battery life is pretty average, however, with me seeing around 3 hours and 45 minutes per listening session.

Overall I think KZ has done a good job with the S2. Given the sub-50 USD price tag (even less right now through the Indigogo campaign) you have to keep expectations in check and with that in mind, the S2 is a success.

Thanks for reading!

- B9

Disclaimer: Thank you to Lillian with Linsoul for reaching out to see if I would be interested in reviewing the S2, and for arranging a sample for coverage. The thoughts within this review are my own subjective opinions and do not represent Knowledge Zenith or Linsoul. At the time of writing the S2 was going through an Indigogo campaign. You can check it out at the links below.

https://www.linsoul.com/pages/kz-s2

https://www.indiegogo.com/projects/kz-s2-next-generation-hybrid-tws-in-ear-monitors#/

Specifications
  • Driver: 7mm dual-magnet dynamic + KZ 30095 balanced armature
  • Chip: Realtek 8763
  • Codec: AAC
  • Bluetooth: 5.0
  • Range: 15+ meters
  • Frequency Response: 10Hz – 20kHz
  • Earbud Battery: 40mA
  • Case Battery: 500mA
  • Charge Times: 2hr earphones / 2hr case
  • Battery life: 4hr music (up to 18 with case) / 2hr talk time (up to 12 with case)
Devices Used For Testing LG G5, LG G6, LG Q70, Asus FX53V

Some Test Tunes

Supertramp – Crime of the Century
Slipknot – Vol 3 (The Subliminal Verses)
Daft Punk – Random Access Memories
Aesop Rock – The Impossible Kid
King Crimson – Lark's Tongues in Aspic
King Crimson – Starless and Bible Black
Infected Mushroom – Legend of the Black Shawarma
The Prodigy – The Day is My Enemy
Steely Dan – The Royal Scam
Porcupine Tree – Stupid Dreams
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