How We Research
We compare products from their published specs and features; the verdicts below are our independent editorial opinions.
If you want a hybrid dual-driver in-ear with an electrostatic tweeter feeding a huge, airy soundstage, choose QZXYHYN KZ ZEX Earphones; if you need a single 10mm dynamic driver with a warm, easy-to-drive tuning and swappable nozzles, choose Kefine Delci 10mm. Both are wired 3.5mm in-ears built around a 10mm dynamic unit, but they chase two very different goals — and that difference is the whole story here.
• KZ ZEX biggest strength: A true hybrid setup — a 10mm dual-magnetic dynamic driver handling the low end plus a 6.8mm low-voltage electrostatic unit for the highs, which is a rare configuration at this tier and gives the ZEX its wide, detail-forward character.
• KZ ZEX biggest trade-off: More moving parts means a more particular fit and a more source-sensitive signature; the electrostatic treble can come across as bright on lean recordings, and the 25Ω / 103dB spec means it likes a bit more clean power than the easiest IEMs.
• Kefine Delci biggest strength: One well-executed 10mm DLC+PU composite diaphragm in a dual-cavity aluminum shell, tuned to be smooth and non-fatiguing, with interchangeable tuning nozzles and a 26Ω impedance that plays nicely with a plain phone or dongle.
• Kefine Delci biggest trade-off: It gives up the electrostatic air and the 40KHz top-end extension of the ZEX, and its sound is deliberately relaxed rather than analytical — if you want maximum sparkle, it's the wrong tool.
• Who each is for: Pick the KZ ZEX if you want a hybrid, detail-rich, big-stage listen and don't mind a fussier fit. Pick the Kefine Delci if you want a light, comfortable, easy-driving everyday IEM with a relaxed tuning and tuning flexibility.
The KZ ZEX is a hybrid in-ear built around two drivers that split the work. A 10mm dual-magnetic dynamic unit covers the foundation, and a 6.8mm low-voltage electrostatic unit handles the upper frequencies. That combination is the point of the product: electrostatic units are known for quick, fine-grained treble, and pairing one with a dynamic driver is how you get both weight down low and shimmer up top. The claimed frequency range of 20Hz–40KHz tells you the designers were chasing extension at both ends.
The housing mixes resin and zinc alloy, and the fit is described as ergonomic, with a shape meant to sit tight against the auricle for long sessions. The cable is detachable via a 0.75mm C-pin connector, and the pins are gold-plated, which is a practical touch if you like swapping cables or replacing a worn one down the road. You get a 3.5mm plug, a 1.25m cable, a choice of microphone or no-microphone versions, and the listing notes adaptive noise cancellation plus app and remote control as control methods.
Who should buy it? In my opinion, the ZEX suits listeners who want to hear the inner layers of a track — acoustic recordings, layered electronic production, anything where reverb tails and cymbal decay matter — and who are willing to spend a few minutes getting the tip seal right. The 25Ω impedance and 103dB/mW sensitivity aren't hard to drive, but they're not the easiest either, so a dongle DAC or a decent phone output will show it at its best.
Who should skip it? If you want a set-and-forget IEM that sounds smooth no matter what you feed it, or if you strongly prefer a warm, rolled-off top end, the ZEX's detail-first hybrid tuning may wear on you. It's a listener's earphone, not a background-noise earphone.
The Delci takes the opposite approach: one driver, done carefully. Its 10mm dynamic driver uses a composite diaphragm that combines Diamond-Like Carbon for crispness with PU for a fuller, more relaxed low end. That's a deliberate blend — DLC alone can sound stiff and bright, PU alone can sound soft, and the pairing is meant to land somewhere in the middle: clear but never harsh, with genuinely deep sub-bass. A dual-cavity structure manages airflow inside the shell to widen the stage and give the bass some punch.
Everything about the physical design points to comfort. Each earbud is machined from aviation-grade aluminum — CNC'd from a single block — and weighs about 5.3g, which is roughly half what a die-cast metal shell would weigh. The gunmetal anodized finish is described as scratch-resistant. The cable is a 1.2m silver-plated copper design with 164 cores, detachable at a 0.78mm 2-pin interface, so upgrades are easy. Impedance is 26Ω with 108dB sensitivity and a 20Hz–20KHz range, which is exactly the profile of an IEM that runs happily straight from a phone.
Kefine also includes six pairs of eartips in two styles — Bullet tips for more bass, Bowl tips for more transparency — plus a hard-shell case. That's a tuning kit in the box, and it's the kind of detail that matters more than any single spec.
Who should buy it? If you wear IEMs for hours at a time — commuting, working, gaming, or just listening all evening — the low weight and smooth tuning make the Delci an easy recommendation. In my opinion it's the better pick for anyone who wants one earphone that behaves well with everything and doesn't demand a dedicated amp.
Who should skip it? If your priority is maximum treble sparkle and the widest possible sense of air, the Delci's relaxed presentation and 20KHz ceiling won't scratch that itch. That's the ZEX's territory.
• Best for a hybrid, detail-forward sound → QZXYHYN KZ ZEX Earphones. The 10mm dynamic plus 6.8mm electrostatic combination is the reason to buy it.
• Best for an easy, relaxed, all-day listen → Kefine Delci 10mm. The DLC+PU diaphragm is tuned smooth and non-fatiguing.
• Best for long wearing comfort → Kefine Delci 10mm. About 5.3g per earbud in CNC aluminum is hard to beat.
• Best for wide treble extension → QZXYHYN KZ ZEX Earphones. Its stated 20Hz–40KHz range reaches further up than the Delci's 20Hz–20KHz.
• Best for tuning flexibility out of the box → Kefine Delci 10mm. Six pairs of eartips in two styles (Bullet for bass, Bowl for clarity) plus interchangeable nozzles.
• Best for cable upgrades → Both, but differently. The ZEX uses a 0.75mm C-pin with gold plating; the Delci uses a 0.78mm 2-pin on a 164-core silver-plated cable.
• Best for plug-and-play with a phone → Kefine Delci 10mm. 26Ω and 108dB sensitivity is about as friendly as wired IEMs get.
• Best for buyers chasing a distinctive, "big stage" character → QZXYHYN KZ ZEX Earphones. The electrostatic unit is what separates it from a crowded field of single-dynamic designs.
If I were buying one of these for myself, I'd take the Kefine Delci 10mm. The reason is simple: it does the fundamentals well — a genuinely light aluminum shell, a 10mm DLC+PU driver tuned to stay pleasant over long sessions, an easy 26Ω load, a quality detachable cable, and a box full of eartips so I can dial in the sound without buying anything extra. It's the earphone I'd reach for without thinking.
The KZ ZEX is the more interesting product, though, and I'd recommend it without hesitation to anyone who specifically wants a hybrid electrostatic setup and the airy, detail-heavy presentation that comes with it. It asks a little more of your source and your fit, and gives back a sound signature the Delci simply can't match.
FAQ
A 10mm driver earbud is an in-ear headphone whose main speaker unit — the dynamic driver — has a diaphragm roughly 10 millimeters across. Both earphones here use a 10mm dynamic driver, though the KZ ZEX pairs its 10mm unit with an additional 6.8mm electrostatic driver, while the Kefine Delci uses a single 10mm DLC+PU dynamic driver.
is 10mm driver good for earbuds
Yes — 10mm is a very common and well-balanced size for in-ear monitors. It's large enough to move a decent amount of air for bass, but small enough to fit comfortably in a normal ear canal. Both the ZEX and the Delci are built around a 10mm driver, which shows how widely the size is trusted in this category.
is 6mm driver good for earbuds
A 6mm driver can work well, but it's usually used as a supporting unit rather than the main one, because smaller diaphragms move less air and tend to produce lighter bass. That's exactly how the KZ ZEX uses its 6.8mm electrostatic unit — not alone, but alongside a 10mm dynamic driver to handle the upper frequencies where a small, fast driver excels.
The KZ ZEX is a hybrid with a 10mm dynamic driver plus a 6.8mm electrostatic driver, giving it wider stated treble extension and a more analytical character. The Kefine Delci is a single 10mm DLC+PU dynamic driver tuned to be smooth and non-fatiguing, with a lighter aluminum shell and swappable tuning nozzles. Check the current price on Amazon for both before deciding.
As an Amazon Associate I earn from qualifying purchases.
We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon and affiliated sites.
When you buy through links on this page, we may earn a commission from qualifying purchases at no extra cost to you.
Amazon and the Amazon logo are trademarks of Amazon or its affiliates. This site is an independent third-party review and is not affiliated with, endorsed by, or sponsored by Amazon or the product brands mentioned.
See also: BBTO 100 vs Microsoft Modern: On Ear Headset, Shure SRH1440 vs Pioneer DJ Professional DJ Headphones, ZenSona Labs Noise Reducing Earbuds vs tahoesleep 3D, Redzoo Neckband Headphones vs dbsono Active Noise Cancelling