Review: Soranik ION-4X CIEM


The Soranik ION-4X is rated at 31.5 Ohms with a sensitivity rating of 99dB/mW @1kHz. This isn’t a difficult IEM to drive; any standard dongle DAC/Amp would suffice. Because of its low mechanical impedance, scalability is naturally capped by its modest impedance, which limits the ability to reach a higher damping factor (control over the drivers).

However, the ION-4X pairs well with warmer and natural sources for an ideal timbral match. Detail retrieval, as one would expect, scales with the quality of the DAC it is being paired with.


Astell & Kern Zero1

AK Zero1 IEM sitting on a sink handle in Black and White


Astell & Kern is no stranger to the sphere of opulent Hi-fi, with an underlying focus on designing and manufacturing frontier-pushing digital audio players (DAPs), with each iterative release an improvement over the next. In their tenure, they’ve released a plethora of strategic collaborations with the likes of Jerry Harvey Audio and Empire Ears, releasing reinterpretations of already-released IEMs.

The Astell & Kern Zero 1 is their independent foray into the IEM marketplace, utilising a tribrid architecture comprised of dual custom-balanced armatures, a single planar-magnetic driver and a 5.6mm dynamic driver — all powered by an active-crossover divvying up the entire frequency band into different sub-sections.


The Zero1 is an aggressively-tuned U-shaped IEM with a brighter-presence region for exaggerated micro-detailing, followed by a neutral mid-bass response with intense PRAT and guttural punch. To put it tersely, the Zero1 is miles apart in terms of tone, balance and timbre in comparison to the ION-4X.

The Zero1’s brighter-treble response ups the ante by extricating missing micro details that highlight the zestiness and zinginess of odd-harmonics. While detailing is plentiful, so is sibilance. Discomfort and unpleasantries emerge more often on poorly-mastered recordings, which is essentially the majority of mainstream releases.

The ION-4X averts this pervasive pain point but effectively highlights the less-acerbic tones in the presence region by emphasising the lower instead of upper treble. Tonally, the ION-4X prioritises grounded reality instead of the “hyper-reality” that the Zero1 promotes with its in-your-face tuning.

The same goes for its low-end response. Intense PRAT with lightning fast-attack in the mid-bass on the Zero1 creates an ultra-exciting macrodynamic presentation, where the obvious contrast between the top and bottom breeds an environment complementary to electronic-based compositions. There’s no denying that the Zero1 supersedes the ION-4X in this regard, but the ION-4X is more adaptive in terms of genre preferences. For instance, the ION-4X’s bass response digs deeper, where bass textures are more pronounced for a slower PRAT — qualities that lend themselves brilliantly well to Americana where acoustic guitars reign supreme.

On a technical level, both IEMs are comparatively impressive, where both products win brownie points for differing reasons. Firstly, the ION-4X wins in the soundstage department, with strong Z-axis distance and out-of-ear width. Conversely, the Zero1 is more proficient in imaging and separation because of its softer sub-bass focus, avoiding the pitfalls of a congested monolithic presentation that compresses vocal and instrumental cues into one box.

Conclusive Remarks

The ION-4X bears the hallmarks of an IEM from a mature brand. Intelligently conceived to merge a “neutral” tuning with enough consumer-focused elements (ala bass), the ION-4X achieves just that with a flair for technical performance. Regardless of what music you play on it, everything appears real. Nothing is offensive or dull.

The infinite array of customisation options and masterful construction doesn’t hurt either. This is an excellent expression of what CIEM could be and should be at any price point. Soranik may not be a household name in our rapidly expanding industry, but it’s staying on for good reason. The ION-4X is one of those reasons.



Picture of Kevin Goh

Kevin Goh

Raised in Southeast Asia’s largest portable-audio market, Kevin’s interest in high-end audio has grown alongside it as the industry flourishes. His pursuit of “perfect sound” began in the heydays of Jaben in Singapore at the age of just 10 years old. Kevin believes that we live in a golden age of readily accessible, quality audio.


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