Knowledge Zenith (KZ) is a company known to pretty much everyone who’s into ChiFi or budget portable audio. But for those who don’t know, KZ is a Chinese earphone manufacturing powerhouse specializing in affordable in-ear monitors. In this review, I’m checking out the new KZ S2 TWS earbuds. The S2 feature hybrid dual-drivers (1 dynamic and 1 balanced armature), Bluetooth 5.0 and IPX5 water resistance rating.

KZ’s previous attempts at TWS had mixed results. I previously reviewed the KZ E10 TWS here which had some pretty serious connectivity issues. So when asked if I would review the KZ S2 I was a little hesitant. Well, I needn’t have worried. Read on to find out why.

Disclaimer: This sample was provided for the purpose of an honest review. All observations and opinions here are my own based on my experience with the product.

KZ S2 Review

Package and Accessories

The S2 comes in a sensibly small white box with a diagram of the earbuds on the front. As soon as you open the box you see the charging case which is seated in a white plastic insert. The other accessories are, of course, beneath the insert. Let’s take a look at what’s inside the box.

• KZ S2 TWS earphones
• USB Type-C charging cable
• Charging case
• 2 pairs of medium silicone eartips
• User’s manual & warranty card

That’s a fairly standard bundle for a TWS earbud but why are there only 2 pairs of eartips provided? Not just that but why are both pairs the same size? This seems like such a poor oversight and I can’t imagine what was going on in the mind of the person who made the decision to do that.

Design and Functionality

The KZ S2 TWS are made of lightweight plastic, similar to the previous E10 model but obviously without the ear hooks. A glossy black finish covers the majority of the earbuds except for the capacitive touch button on the faceplate which has a matte finish and KZ logo.

The nozzles are aluminium and have a standard width which means you can use a wide variety of third-party eartips with them (which I think a whole lot of people will end up doing). When you take the earpieces out of the charging case they automatically connect to each other and then go into pairing mode.

I found the touch controls to be quite good on the S2, especially since the buttons don’t seem as sensitive as other TWS buds which means less accidental presses. The controls are fairly standard so you’ll feel right at home if you’ve used any TWS previously. There are no volume controls on the earbuds so you’ll need to do that from your phone. However, all other functions can be done from the earbuds themselves.

Charging Case

The charging case is a big improvement over the E10’s. It’s smaller and much more pocketable plus it has a spring-loaded mechanism with a magnetic seal. One thing I really like about this charging case is that it can accommodate larger eartips, even some of my XL tips fit in there just fine.

On the bottom is the Type-C USB port for charging. It seems a bit strange to place it there, mainly because the charging LED indicator is located inside the top of the case. On the back of the case is a small button that shows the current battery level. It glows either green, amber or red depending on how much charge there is.

Comfort and Noise Isolation

For my ears, the S2 are very comfortable, although they are fairly big and so protrude out from the ears a bit. They feel nice and secure in my ears and I had no problem going for a run with them. Noise isolation is about average for this type of earpiece meaning you can still hear things around you unless you are blasting your music.

Connectivity, Battery LIfe and Call Quality

Unlike the KZ E10, the S2 worked perfectly for me in terms of connectivity. Pairing with multiple devices was easy and trouble-free. I didn’t experience any signal drops or disconnections at all, so it seems KZ has that sorted for now.

When it comes to battery life, the S2 buds are good for around 3.5-4 hours on a full charge. They can be fully recharged 3-4 times in the case. Charging for both the earbuds and the case is about 2 hours.

Voice quality for phone calls is reasonably good, although it does pick up a lot of external noise. If you’re somewhere noisy it might be difficult for others to hear what you’re saying but otherwise it works fine.

Sound

Sources used for testing include the FiiO M6, Shanling Q1 and my Galaxy Note smartphone. Pairing was quick and easy on all devices. Assuming that 2 of the 3 sources had Bluetooth turned off, the S2 would automatically connect to whichever device had Bluetooth turned on when I took them out of the charging case.

The general sound signature is slightly V-shaped with lifted bass and treble with a slightly recessed midrange. Clarity is very good – an area where a lot of TWS earphones disappoint but the S2 is clear as day. Tonally, the presentation leans toward the brighter side of neutral but it’s not harsh or unpleasant in the least.

Bass

Bass is tight and fairly fast with an emphasis on the mid-bass. But the S2 also has a reassuring and solid sub-bass rumble that extends as well as any budget TWS I’ve heard. The bass is among the cleanest I’ve listened to on a TWS earphone so far. It has a fairly fast attack and a natural decay.

I wouldn’t call these a basshead in-ear but there’s plenty of juice in the trunk to drive the music along. I would actually consider it quite a mature bass and one that is punchy but tight. It sounds great across multiple genres from jazz to hip-hop. Tupac’s “Can’t C Me” is a lively, funky track with a reasonably prominent bass but the S2 handles it like a champ. It packs a punch without any significant bleed into the midrange.

Mids

The midrange is a bit lean with a smallish note size and fast transients. Unlike a lot of TWS buds, the S2 has great midrange clarity without any muddiness. Male vocals are slightly thin and could use a touch more body for realism. Female vocals sound more natural and are quite vibrant. Playing London Grammar’s “Rooting For You”, Hannah Reid’s vocals sound clear and lively.

Treble

The S2’s treble sits forward in the mix and is thus quite prominent. While it provides excellent detail retrieval and clarity it can sound a bit splashy. If you’re treble-sensitive you may want to look at alternatives but otherwise, you should be fine.

It works better with certain genres than others. For example, S2 generally sounds great with hip-hop and pop but for some rock and metal, it might not be a great match. For example, I found the cymbals in the chorus of Katatonia’s “Buildings”, too harsh for my preference.

Soundstage

In terms of imaging, the S2 is fairly average when it comes to positional cues. Stage dimensions are modest, sounding like a wide but fairly shallow room.

Conclusion

Overall, I think the KZ S2 is a winner. The build quality and battery life are fairly good and the Bluetooth functionality has worked perfectly for me during testing. I would strongly recommend that anybody considering these buy some additional eartips if you don’t have some spares already, as you’ll be stuck if the 1 size included don’t fit your ears properly. With that aside, unless you’re really treble sensitive, I think these are absolutely a steal, especially if you get them at the special launch price of $29. Good job KZ!

eartips WTF

Specifications

• Drivers: 7mm double magnetic dynamic driver + custom KZ 30095 balanced armature driver
• Bluetooth chip: Realtek 8763
• Bluetooth version: 5.0
• Bluetooth codec: AAC
• IPX Rating: IPX5
• Frequency response: 10Hz-20kHz
• Earbud battery: 40 mA
• Case battery: 500 mA
• Earbuds charge time: 2 hours
• Case charge time: 2 hours