KZ ups the ante in the IEM driver and tuning switch wars – tour de force or torment?
Just when I thought the driver wars were ending, KZ released the AS24 with 12 balanced armature drivers per side. Then KZ upped the ante in the tuning switch wars with eight tuning switches per side, further fueling the competition.
Are the driver and tuning switch wars ending? Or just beginning?
Unboxing and First Impression
KZ (Knowledge Zenith), based in Dongguan City, China, began as a distinct brand in 2013. In 2018, KZ gained complete independence in research and development with their own factory and provided customers with a full complement of OEM/ODM products and services, including wired and wireless IEMs and headphones.
- Style: In-ear monitor
- Drivers: 12 balanced armatures per side; 29689 BA x2; 31736 BA x4 (each 31736 BA = 30019 BA x2); 30019 BA, 22955 BA
- Impedance: 20-50 ohms
- Sensitivity: 109±5 dB/mW
- Frequency Response Range: 20Hz – 40kHz
- Plug Type: 3.5mm gold-plated connector
- Pin Type: 0.75mm 2-pin
- Cable Length and Type: 1.2m (4 ft) high-purity silver-plated OFC (Oxygen-free Copper core) wire and pre-shaped ear hooks
- Color: Gunmetal/Silver
- Weight: 8g per IEM (including ear tip)
The small, plain black box is functional and efficient. KZ claims that the box and materials are a more environmentally friendly solution. Small, simple, neat, and efficient. Accessories are minimal, with a few ear tips, a cable, and a tool to adjust the tuning switches. There is no carry case included.
In the box
- KZ AS24 IEMs
- Three pairs of silicone ear tips (S, M, L)
- One pair of foam tips
- SIM card removal tool
- Pamphlet/quick start guide
The 1.2m high-purity silver-plated OFC flat cable is attractive and light in weight and appearance. The cable seems high-quality, a significant step above the usual functional yet flimsy cables accompanying most entry-level IEMs. The 2-pin connection fits perfectly and is secure.
There are zero microphonics, which is literally music to my ears and yours.
The “flat” cable is two wires bound side-by-side from the plug to the splitter, resulting in a feel of being flat. The left and right cables then separate into single round wires. The cable is relatively tangle-free and feels quite strong. Unlike braided cables, there is nothing to come loose with regular use.
The cable’s ear hooks are highly secure, if a bit stiff, resulting in a snug fit. Until they soften a bit, the ear hook pressure can compromise a good IEM seal. I experienced this until I found the best-fitting ear tips and used the cable enough to soften up the hooks.
Build & Design
The build feels well-made, and the fit and finish are excellent. There are no rough edges. The ergonomic shape is helpful to offset the size and weight. The AS24’s face is attractive in person and doubles as ear jewelry.
The AS24’s body is comprised of several main pieces: a DLP 3D printed lightweight, skin-friendly resin body, and high-precision integrated acoustic filtering nozzle, a sparkling diamond-cut bracket, and a light metal front cover.
The nozzle is of average-long length, with a notched collar to secure the ear tips, which helps with deeper insertion to offset the physical size of the bodies. A metal acoustic filter is positioned at the end of the nozzle.
Two versions of the AS24 are available – tunable and non-tunable.
The tunable edition will be a great source of debate for the AS24. There are four primary (Main) and four secondary (Auxiliary) switches per side. If you have a hawk’s eyesight (or a jeweler’s loupe), and a surgeon’s steady hand with the provided SIM card removal tool, you can adjust them.
Their low weight (for their size) and ergonomic shape make them manageable. The form gives me no discomfort by itself, other than adjusting them periodically to keep them from angling out and compromising the seal.
The AS24 are not for small dainty ears.
The upside of the size is that the bodies are easy to handle and adjust. The shells feel substantial in hand. Thanks to excellent ergonomics, the body makes no contact with my outer ear, and they do not feel heavy in my ears. I can wear them for hours without bother or fatigue.
The AS24 has 12 BA drivers per side of varying types and specific jobs to perform:
- 29689 BA x2 = 2 BA for mid-frequencies
- 31736 BA x4 = 8 BA (each 31736 BA = 30019 BA x2) for high and ultra-high frequencies (treble and “air”)
- 30019 BA x1 = 1 BA for high-frequencies (treble)
- 22955 BA x1 = 1 BA for low-frequencies (bass)
KZ AS24 Sound
For evaluation, I listen to a great variety of music through numerous sources, including:
- Sony DVP-S7000 CD Player
- LG V20 & LG V60 phones (both have Quad DAC and headphone jacks)
- Google Pixel 7 Pro
- Lenovo IdeaPad 3
- Khadas Tone2 Pro
- Khadas Tea
- S.M.S.L SP200 Headphone Amplifier
- HIFIMAN EF400 Headphone Amplifier
- HELM Audio Bolt and DB12 AAAMP
With a low impedance of 20-50 ohms and a high sensitivity of 109±5dB, the AS24 are very easy to drive. Insertion depth is average and will yield above-average passive sound isolation with adequately seated and sealed ear tips.
I have not had success with the provided tips, especially the foam. Comfort came at the cost of choking off the sound transfer into my ear canals. My preferred tips are a borrowed pair of silicone tips from the Bang & Olufsen Beoplay H3 and silicone YINYOO Tri Clarion tips.
After listening to the AS24 with all switches off, I began the tedious (for me) task of toggling through myriad combinations. Now, I am happiest and most engaged with all switches on.
The tuning switches don’t radically alter the sound or timbre.
As a result, my opinions apply to the overall sound of the AS24, regardless of switch configuration.
The frequency response is well done in all configurations. The sound signature is mature and balanced. The AS24’s sound is highly detailed with crisp clarity, better than most dynamic drivers can manage. All the while, transitions remain smooth. The crossovers are so well executed that the resulting coherence is truly surprising.
If you like to tinker, the tuning switches will let you make small changes to the frequency response to your heart’s content.
The AS24 exhibit excellent dynamics with nuance. The soundstage is spacious, and the imaging is precise. Well-timed attack and decay make for realistic timbre and good tonality, which is quite an accomplishment for all-BA driver IEMs (especially with 12/side!).
For this review, I visited the following artists and their home locations:
- Moldova: Dying Light by Infected Rain
- Morocco: Amour – Ou Trop Tard Me Suis Pris by Amina Alaoui
- England: Il Mio Cuore Va by Sarah Brightman
- United States: Mirror Haus by Lindsey Stirling
- Netherlands: Wireless by Within Temptation
A fascinating collection from several continents, these diverse musical productions range in ethnic origins, musical styles, and explorations in audio.
For a BA driver, the bass reproduction is authoritative and rich while remaining clean and well-defined. When all switches are on, the upper bass can slightly step on the midrange with specific compositions. Note weight is slightly thin if you prefer warm, thick, bass-heavy sound signatures.
What the bass lacks in sheer quantity, it easily makes up for in quality and musicality.
Bass delivery is satisfying and appropriate for almost all genres. The bass extension is deep with no roll-off. I heard no distortion when listening at moderate to loud volumes (for testing). They remind me of planar drivers with a slightly less sharp attack.
Resolution and texture are excellent for natural instruments such as cello, upright bass, and timpani.
The midrange sounds natural, clear, and full-bodied in all music. You will be delighted with the AS24 if you primarily listen to vocal-centric music. Despite what the graph may suggest, the mids never shy toward the back. They are smooth and do not come across as shouty.
I am impressed with the treble tuning and capability. The treble is lively, revealing, and detailed without causing fatigue. I have yet to be offended by sibilance, odd BA sharpness, or unwanted shimmer. The treble brings perfect balance to the rich, musical bass.
Where to Buy
The AS24 are genuinely excellent, with few reservations. They are an easy recommendation, especially with such a favorable price-performance ratio. I can’t imagine anyone being disappointed with the AS24 unless the size and fit do not work or someone is looking for IEMs with a distinct signature strength (e.g., powerful, ear-drum rattling bass).
KZ is entering a new era of maturity in its product development and tuning to appeal to a more discerning audio-enthusiast audience of prolific buyers who add new IEMs regularly to their collections.
For tinkerers, the tuning switches will provide countless hours of fun. Toggling switches on and off will be incredibly engaging, entertaining, and satisfying. For others, this may be an irritating chore that could be more quickly accomplished through software-based EQ.
The AS24 are mature, balanced, and highly flexible if you have the time and patience to experiment with myriad subtle sound difference possibilities.