Today we’re checking out a modern update to a classic KZ.
The original ZST was a landmark product and KZ’s first foray into hybrid earphones. It inspired an entire segment of equally budget-friendly hybrid competitors, a market that today is alive and well, teeming with new models. Prior to the release of the ZST, fans of the brand had been relentlessly asking KZ to dip their toes into the hybrid market. The consensus seemed to be that KZ had no intention of doing so. Balanced armatures (BAs) were still too pricey, meaning their implementation would drive the price above the market KZ was dominating and comfortable in. Times have clearly changed. Hybrids are now KZ’s bread and butter with pure dynamic based earphones being a rarity, their release outpaced even by pure-armature models.
The ZST X revives the ZST name while also retaining key features and characteristics of the original; 1+1 hybrid, low profile shell, low price, and removable 2-pin cables. Is it a worthy successor to the landmark product that was the ZST? Let’s find out.
What I Hear The ZST X is a welcome update to the original ZST with one change in particular that elevates it over it’s predecessor.
Treble is one area where the two differ most. Upper treble is pretty similar with both offering a decent amount of sparkle and air between notes. The ZST X’s newer drivers do sound a bit smoother and more refined. Leading into the low treble is where the two separate, and the ZST X comes into it’s own. The 4K rise of the ZST X brings in plenty of detail and clarity for a budget offering. The original ZST falls far behind in this regard giving listeners a lower resolution, more analogue-like sound. I also find the ZST X to sound quite quick with a rapid attack and equally snappy decay.
The mids of the ZST X are very crisp and coherent with a fairly equal representation for male and female vocals. Note weight is moderate, with a more lean, moderately brighter sound than the original ZST. The ZST X has great clarity with a solid ability to pull micro-detail. It is certainly a step up from it’s predecessor which comes across overly smooth and lacking in fine detail in comparison. Timbre on neither is completely accurate with the ZST X having the advantage. While a touch bright, it is lacking the artificial edge pasted across most of the ZST’s auditory spectrum.
Bass on the two is very similar in terms of balance and linearity when transitioning from sub-bass regions and up into the lower mids. The ZST X’s low end is even more elevated than the original ZST, bringing along with it additional texture. Note control is also quite good for a budget earphone with no sloppiness or bloat to speak of, except on tracks that are particularly mid-bassy. Extension is excellent with sub-bass notes providing plenty of physical feedback. The original ZST falls behind here too. The ZST X’s ability to handle congested tracks is good, but tossing the rapid double bass common to speed metal trips it up. The original ZST doesn’t fall far behind. Texturing on the ZST X is also quite good but falls short of the best-in-class. The original ZST is overshadowed.
When it comes to sound stage the ZST X provides a decently spacious experience that keeps up with other products in this price range. I find the staging deeper than it is wide with excellent layering and good instrument separation. Imaging is quite satisfying with fairly nuanced channel-to-channel movement. They work fine for gaming, but I wouldn’t reply on them for pinpoint accuracy. In comparison, the original ZST sounds a little wider but not nearly as deep. Its imaging is more vague and lacking the same level of accuracy. The ZST doesn’t layer as well either, nor are instruments as well separated. Staging qualities are where the ZST truly shows it age and is most outclassed.
Overall I find the ZST X to be a pretty significant upgrade on a technical level. It’s staging qualities are notably better and it’s detail retrieval and clarity are vastly improved. That said, I quite enjoy the ZST’s smooth sound and fairly relaxed presentation and can see some preferring it to the Xs more lively sound.
Compared To A Peer (volumes matched with Dayton iMM-6)
KZ ZS4 (~18 USD): The ZS4 is a quite a bit more v-shaped and bassy than the already bassy ZST X. Both models bias towards sub-bass with excellent extension, with the ZST X sounding more linear as you head into the lower mids. The ZS4’s low end is a bit smoother and slower sounding than the ZSTX which better handles quick notes. It also feels more textured though the differences are minimal. Mids on the ZST X are more weighty and forward with less of a rise heading into the upper mids. I actually find the ZS4 to sound slightly more timbre-accurate with the ZST X applying a wooden, blunted edge to some instruments. That said, vocals on the ZS4 do have a somewhat breathy quality to them which may bother some. Heading into the treble, the ZS4 has a clear bias towards the brilliance region making it quite a bit more sparkly and vibrant. It really highlights the v-shaped signature. The dip in the presence region also put it at a significant disadvantage in terms of detail output. In terms of sibilance, I hear it on both. It appears more often on the ZS4, but the ZST X’s is sharper and more unpleasant. Sound stage is wider and deeper on the ZS4 but feels much less dynamic and more flat than what I hear from the ZST X. The ZST X offers better imaging, layering, and separation qualities too.
I appreciate the raised mids, improved technical ability, and overall more even sound of the ZST X. The ZS4’s abundant low end is pretty fun though, and I like the shells a lot, even if they’re not quite as comfortable as the ZST X’s tried and true shape.
KB EAR KB04 (~30 USD): Comparisons to the KB04 are very similar to the ZS4. The KB EAR is notably bassier but like the ZST X has a sub-bass bias. While the bass performance in the ZST X is good, the KB04 is even tighter and punchier. That could come down to the driver tech, the dense metal housings, or a combination of the two. The KB04 has even better texturing too. Heading into the mids the ZST X pulls itself back into contention. While they both have a bump to upper mid emphasis, the ZST X’s rise is more gradual and retains a more linear emphasis through into the treble regions. Along with being less fatiguing, the ZST X’s timbre is more accurate, missing the dry, crispy nature of the KB04. Treble presentation is similar but I prefer the ZST X. Notes are a bit thicker, tighter, and better controlled with less overall emphasis that is more effectively balanced out by the abundant low end. Sound stage on the ZST X is a little bit wider and deeper with similar imaging quality. The KB04 offers up slightly improved layering and instrument separation.
Overall I prefer the less aggressively v-shaped sound of the ZST X. It’s not as well built but it’s a lot lighter, more ergonomic and comfortable, and as a budget friendly all-rounder is simply more enjoyable to use.
In The Ear The ZST X is built the same as the original ZST, more or less. Higher quality acrylics have been employed for the main body and face plate with the completely clear design mimicking that of the purple ZST Colourful that came out later in the earphone’s lifespan. While I prefer the somewhat cheesy looking faux carbon-fibre face plate on the earliest ZST models, the simpler design of the new X version looks nice. Unlike the ZST X’s more expensive counsins (ZSN, ZSN Pro, ZSN Pro X) the 2-pin ports are not screwed in place. Instead the somewhat complicated inner moulding keeps everything where it needs to be. The plastic nozzles of the original ZST make a return and do a fine job of holding most standard sized tips securely in place. All together, the ZST X ends up looking and feeling quite decent, especially given the low price tag.
The cable is a straight upgrade from previous KZs, including the similar looking silver-plated cable that was available as an upgrade. The sheath is thicker, more plush, and less prone to tangling above the y-split. The silver-plated wiring within has a nice sheen to it too. It looks and feels quite nice. The hardware falls into the “same old, same old” category though. The VSonic inspired y-split and jack carry over from earlier KZ’s, as do the excellent preformed ear guides. Overall a great stock cable and quite welcome on a budget model.
Comfort is outstanding for me. This earpiece has been a staple across a couple brands in my experience with mild tweaks being made to the nozzle angle and quality of the plastics. With the ZST X, it fits perfectly with little to no effort required to get and maintain a good seal. The super lightweight, all-plastic design works in it’s favour too. The preformed guides hold the cable securely around the ear resulting in an earphone that is very stable under extreme movement. If you have small outer ears or they’re a particularly odd shape you might have issues with fit and comfort, but I expect everyone else to find these a pleasant product to wear.
Isolation is basically the same as the original ZST based on my time with the two products. Any differences are hardly noticeable. With no music on and a Youtube video playing on my laptop in the background at my normal listening volumes, everything was still audible and I could follow along, but just barely. Using them in my local coffee shop requires a mild increase in volume to compensate, but nothing extreme. In general, bringing music into the equation makes outside noise a non-issue, especially if you opt to toss on some third party foam tips.
In The Box The ZST X arrives in the same style of packaging as the majority of KZ’s modern offerings. The white exterior sheath features a coloured digital rendering of the ZST X’s ear pieces as well as model info, while on the back you find specifications as well as locations and contact information for KZ. Sliding off the sheath reveals the ZST X’s ear pieces set within a paper covered foam insert protected by a clear viewing lid. Lifting it all out you find the accessories below. In all you get:
- ZST X earphones
- 0.75mm 2-pin silver-plated braided cable
- Starline silicone tips (s/m/l)
- Manual and warranty card
This is a very standard accessory kit from KZ. I always like seeing ‘Starline’ tips included. They’re made from a very durable, flexible, high quality silicone. For most models in their lineup they pair very well and provide a good seal. As always, it would be nice of them to include a case or carrying bag, but for the price I can’t be too disappointed. The one unexpected and welcome addition is that silver-plated cable. It’s thicker than both KZ’s standard copper braided cable and their older upgraded silver-plated option. This cable also goes back to KZ’s recessed 2-pin style moving away from the QDC raised plugs they’ve been using lately (some of you will be very happy about that). The excellent preformed ear guides they’ve had equipped to their cables for a while now also remain, continuing on their decision to forgo memory wire.
Final Thoughts Overall I find the ZST X a fantastic update to the original ZST, and a very suitable replacement. It keeps what was great about the original model, namely the comfortable shell, then improves upon it in a number of areas; detail, clarity, bass extension and physical feedback, staging airiness and overall technical ability. That said, there are two other models in KZ’s modern lineup that I would recommend picking up over the ZST X.
First is the EDX. At under 10 USD, it provides the same wearing experience thanks to it sharing a shell, though the ZST X comes with KZ’s awesome new silver-plated cable. Sound wise they share pretty much the same signature with the ZST X providing more upper treble energy, detail, clarity. This comes at the expense of timbre which I find the EDX does better. The second I’d take over the ZST X is the DQ6. It once again offers a very similar signature but with all the peaks reduced. This leaves it more balanced and with more accurate timbre. It also looks and feels more premium thanks to the Zinc face plate, though the ZST shell is more comfortable. Well worth the increase in price in my opinion.
Would I recommend the ZST X? Yes, but with the caveat that the EDX and QD6 are unavailable to you. If that’s the case, the ZST X is one of the better sub-20 USD earphones I’ve heard recently and makes for a great daily driver.
Thanks for reading!
Disclaimer A huge thanks to Lillian with Linsoul Audio for arranging a sample of the ZST X for the purposes of review. The thoughts within this review are my own subjective impressions based on months of time with the ZST X. They do not represent KZ, Linsoul, or any other entity. At the time of writing the ZST X was retailing for a mere 17.00 USD: https://www.linsoul.com/products/kz-zst-x
- Frequency Response: 20-40,000Hz
- Impedance: 12 ohms
- Sensitivity: 107dB/mW
- Cable: 0.75mm 2-pin
- Driver: One balanced armature, one dynamic per side
Gear Used For Testing LG Q70, FiiO M3 Pro, FiiO BTR3K, Earstudio HUD100, Earmen TR-Amp, Asus FX53V, TEAC HA-501
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
Fleetwood Mac – Rumors
Tobacco – F****d Up Friends