The box is standard KZ fare: it’s small and simple. Inside the box, we find the usual sparse set of accessories including the KZ ESX earphones, a detachable silver-plated flat cable and a few pairs of silicone eartips. There is one additional item in this box though, in the form of a gold commemorative coin. It’s not real gold, but it adds a little excitement to the unboxing and lets people know about KZ’s 10 Anniversary.
The ESX’s cavities are made of a transparent resin that gives you a clear view of the IEM’s internals. KZ has implemented metal alloy faceplates with a cracked design. The faceplates are grey in colour with light blue lines in the fissures. I think most people will agree that the shells look pretty nice.
They’re comfortable too and fit in my ears better than both the DQ6 and ASX (after I swapped out the stock cable with its angled connectors). I can happily wear them for long listening sessions. The passive noise isolation is not bad either: with music playing quietly I can barely hear anything else even in noisy environments.
Once again, we get the standard KZ flat SPC cable. The components are all made of opaque plastic but the handling is decent. However, it tends to get tangled pretty easily.
Considering the KZ ESX is a special 10th-anniversary release, it should be a good one. And to put it bluntly, it is. The ESX has a warm, balanced sound that’s perfect for everyday listening. It reminds me of the good old KZ days and IEMs like the KZ EDR2 and ED9. Those were the days before all the measurement madness when people cared more about how IEMs sound instead of how good they look on a graph. Ironically, I’m about to insert the ESX graph below.
The ESX’s bass is elevated and delivers thumping kick drums along with rumbling sub-bass notes. I wouldn’t quite call it a basshead IEM but it’s leaning in that direction. Thankfully, the quality of the bass is good and it doesn’t dominate or cause any excessive smearing.
You can feel the impact with each note of the rounded, weighted bass. ESX’s lows have the authority and movement of air that dynamic drivers do so well. It not only provides the foundation for the mids and treble but it imbues them with warmth and body.
ESX crafts a warm and full-bodied midrange with the backing of the mid and upper-bass. Male vocals sound rich and sonorous and the same can be said for cellos and lower-register piano notes. It’s an energetic midrange that’s bold enough to be engaging alongside the boosted bass.
The mids are rounded, powerful and slightly on the warmer side of neutral. However, thanks in part to the treble tuning, the midrange still has good clarity and definition. What’s crucial here is the clarity and resolution of the mids that prevent the overall tone from sounding murky.
I’m surprised by ESX’s level of detail; I’m hearing details in the music that a lot of more expensive IEMs completely miss. It’s a result of the clever upper midrange and treble tuning and far better than you might expect with such a full-bodied and warm presentation.
There’s no evidence of the scratchy, grainy treble that so many previous KZ models exhibited; instead, the treble tone is slightly warm and smooth. You won’t hear any sibilance either: the ESX’s treble is boosted enough to be exciting without crossing the line into sharpness.
Soundstage and Technicalities
The soundstage is another area where the ESX performs better than it should; it’s respectably spacious and organized. For a budget IEM, the quality of the dynamic driver is extremely good. As a result, the instrument separation and the overall resolution are good despite the smooth and rounded notes. Imaging is slightly subdued by the thickness of the notes but is still commendable.
I was pleasantly surprised by the KZ ESX. It might not excel in any particular area but more importantly, it doesn’t really do anything wrong. The bass is boosted but still in balance with the mids and treble. The treble is clear and detailed yet still smooth. The ESX is like the best of KZ’s past wrapped in a modern-day shell. Best of all, it’s priced under $20. I think this is the perfect IEM to commemorate KZ’s 10th Anniversary and an easy recommendation for anyone beginning their audiophile journey.