KZ ZSN Pro X - Is it really that bad?

tl;dr: A relic of a (hopefully) bygone era. Surprisingly, it has some positive aspects, such as above-average separation and percussion control. However, and luckily, you can get much better stuff for the same price nowadays. Hard pass unless you are very curious.

Preample

• I purchase this unit on my own. I have no affiliation with or financial interest in KZ.
• All listening tests were conducted at around 65 dB.
• My music library covers nostalgic pop music, epic orchestral music from Sci-fi shows, classical violin performances, piano, lo-fi beats, and a few rock songs.
• What I look for in IEM, in order of importance: a strong sense of depth with elements in a mix layering from closer to further away, clear separation between elements, detailed and textured elements, snappy and tactile note attacks in bass and midrange, natural timbre.
• IEMs are rated with a series of A/B tests against a few benchmark IEMs. The total rating is the average of component ratings. EQ is NOT used in these tests. See the methodology for more detail.
• Eartips can change the insertion depth of an IEM, which in turn changes its soundstage and frequency response. I try to insert IEMs to rest against the concha of my ears unless indicated otherwise.

Non-sound aspects

KZ ZSN Pro X must be one of the most accessible and (in)famous IEMs in the audiophile world. Amazon carries them. DankPods recommends them. Audiophiles dread them. So, how good (or bad) are they, really?

First thing first, what is KZ ZSN Pro X? It is a hybrid IEM with a 10mm dynamic driver and a balanced armature driver. The dynamic driver handles bass and mid, whilst the BA driver delivers high frequency. So, you know which one to blame for that piercing treble response.

Accessories:

• 4 pairs of ear tips
• 2-pin QDC-type cable
• I use the box as the carrying case

Fit-wise, you can choose at least three insertion-depth when wearing ZSN Pro X due to their long nozzles. Deeper insertion gives you a bit more detail whilst reducing soundstage width.

Sound Analysis

This table shows the results of A/B tests between ZSN Pro X and the benchmark IEMs. +1 means the KZ wins. -1 means the KZ loses. 0 means draw. Some tests are too one-sided that I can reach conclusions without further tests.

Note: extra tests against FH3 were conducted during the write-up of this review. The table has not been updated to include these results.

Percussion Control: 3.5/5

Percussion control reflects an IEM’s ability to render drums and other instruments that maintain the rhythm and tempo. IEMs with good percussion control can keep up with fast and complex rhythms without blurring the beats together. IEMs with excellent percussion control give a tactile “snap” to percussion attacks. Percussion control is determined by both bass and treble.

Songs used for A/B tests:

• MS Gundam: Iron-blooded Orphans (1:10 to 1:35): focus on the timing and composure of the bass line during busy section.
• INFINITY (0:40 to 1:05): focus on the timing of bass and cymbal.
• Imperial March (0:00 to 0:45): focus on the timing of percussion and double bass.

ZSN Pro X is surprisingly decent at percussion control. I was surprised that bass does not bleed into the mid, giving ZSN Pro X a clean and lean presentation. Drum hits, such as in INFINITY, are snappy and “fast”, perhaps due to the excessive treble energy.

However, the drum hits do not feel impactful. Despite having a lot of mid-bass in the graph, ZSN Pro does not have a loud “thump” sound of drums. It also does not produce rumbles and physical sensations in your throat like other IEMs with great sub-bass extension.

Speed-wise, ZSN Pro X was also responsive enough to keep up with the Imperial March’s marching rhythm and the complex drum lines in MS Gundam: Iron-blooded Orphans.

Comparison against benchmark IEMs:

• Vs EarPods (1/5): ZSN Pro X wins hands down. It renders drum lines much cleaner.
• Vs Aria (3/5): Aria might be more impactful, but ZSN Pro X is better at the clarity of the drum lines. As we are evaluating percussion control, KZ wins this round.
• Vs ER2SE (4/5): Speed vs speed. ZSN Pro X is more or less in the ballpark with ER2SE, but it is slightly worse in rendering the rhythm lines led by string instruments, so ER2SE wins this round.

From the comparison, I found that ZSN Pro X is somewhere between Aria and ER2SE levels in percussion control. So, I give it 3.5/5.

Detail, Texture, and Micro-dynamic: 2.5/5

Detail, Texture, and Micro-dynamic reflect an IEM’s ability to render fine details in individual elements of a mix. IEMs with excellent detail retrieval render vocal and instruments clearly and reveal small details such as breaths, small vibratos, and the subtle reverb at the end of a musical phrase. They can make the violin section in an orchestra sound like a collection of violins playing together rather than a blob of sound. They also render background elements such as backing vocal and orchestra clearly.

Songs used for A/B tests:

• I have a dream - remix (0:50 to 1:20): focusing on small elements and backing vocal in the background of the mix.
• Memories (0:00 - 0:21): focusing on the texture and micro-details of the guitar.
• My Heart Will Go On (0:00 to 0:40): focusing on the texture and micro-details of the voice, especially the last words of each phrase.

The details and textures that ZSN Pro X manage to pull out of elements in a mix are middling. However, it avoids the overly smoothened vocal and instrumental sound that some BA-based IEMs have.

Comparison against benchmark IEMs:

• Vs EarPods (1/5): ZSN Pro X extract more details and texture from vocal and instruments than EarPods.
• Vs FH3(2/5): ZSN Pro X does not have that overly smoothened, untextured sound in the midrange of FH3.
• Vs Aria (3/5): Aria is simply more detailed and textured than ZSN Pro X. The differences are apparent in the Memories and My Heart Will Go On.

I found that ZSN Pro X is somewhere between FH3 and Aria based on the comparison. So, I give it 2.5/5

Separation and Layering: 3.5/5

separation and layering reflects an IEM’s ability to render elements in a mix distinctively. IEMs with excellent separation and layering can separate elements from left to right and from front to back, minimising the overlap between them.

Songs used for A/B tests:

• And the waltz goes on (0:50 - 0:15): focus on the layering and separation of the instrument.
• Beethoven Symphony No. 5 Mvmt 1 (0:00 to 0:30): focus on the sharpness of instruments, layering of woodwind over the string, and the panning of string from right to the left channel.
• Waltz 2 (0:35 - 1:00): focus on the separation and layering of woodwind over string over percussion.

Surprise surprise: ZSN Pro X is actually decent at instrument separation.

Elements in a mix sound thinner and, therefore, more separated on ZSN Pro X. However, the actual ability of the IEM to render overlapping elements in a mix is only mediocre.

Comparison against benchmark IEMs:

• Vs Aria (3/5): “And the waltz goes on”, and Symphony No. 5 sound cleaner and more separated on KZ.
• Vs ER2SE (4/5): When comparing against a similarly lean sounding IEM, ZSN Pro X is no match.

Based on the comparison, I found that ZSN Pro X is somewhere between Aria and ER2SE. So, I give it 3.5/5

Spatial Illusion: 2.5/5

Spatial illusion reflects an IEM’s ability to construct an imaginary sound field around a listener’s head. IEMs with excellent spatial illusion create a dome-like and open soundstage around the listener’s head.

Songs used for A/B tests:

• Danger Zone (0:00 - 0:50): focus on the centre of the soundstage to see how much it is pushed away from the head.
• Presto (0:00 to 0:40): focus on the reverb. Does it wrap around the head or appear inside the head?
• Shaker test: for drawing out the overall shape of the soundstage.

The soundstage width of ZSN Pro X is as you expect from an IEM. The depth, however, is a bit lacking. Elements in the centre channel might appear in your face rather than in front of you.

Comparison against benchmark IEMs:

• Vs FH3(2/5): Same width, but better depth on KZ. The stage on KZ is not pushed in the listener’s face as much as FH3.
• Vs Aria (3/5): Same width, but less depth. ZSN Pro X cannot create a dome of reverb sounds around the listener’s head like Aria and other IEM with decent depth.

Based on the comparison, I give ZSN Pro X 2.5/5

Tonality: 1/5

Tonality reflects the timbre and relative loudness of different elements in a mix. I assess IEM’s tonality based on how bad they are rather than how good they are. As long as the tuning does not make timbre unrealistic nor reduce technical performance significantly, it is acceptable.

ZSN Pro X does a reasonable job in the bass and midrange region. It traces the frequency response of Aria reasonably. This KZ IEM is not well-tuned, but it certainly does not sound muddy or bloated.

The critical weakness of ZSN Pro X is the treble. This IEM gives all vocals and instruments a metallic timbre that is unnatural and unpleasant.

To make the matter worse, KZ’s treble is also “spiky”, meaning some high notes are much louder than others. Therefore, it is hard to turn the volume up without hurting your ears.

Comparison against benchmark IEMs:

• Vs Apple EarPods (2/5): Wired earbuds from Apple has more pleasant tonality than KZ, despite being more muffled in the midrange. At least, EarPods does not hurt your ears.
• Vs Aria (3/5): Aria is much smoother in the treble region. Therefore, it gives a more natural timbre, and you can turn up the volume without any issue.

Because of the stated problems, ZSN Pro X has 1/5 in tonality.

Personal Preference 2/5

Personal preference is my entirely subjective and personal opinion about an IEM, based on multiple factors. This score DOES NOT contribute to the rating of an IEM.

I appreciate these IEMs for what they represent: a push for more budget-friendly in-ear headphones with exciting technologies.

On some aspects, I think ZSN Pro X was successful. It stomps those bullet-style, cheap earphones in supermarkets and bookstores on both sonic performance and build quality.

With that being said, I find these IEMs uncompelling and, sometimes, uncomfortable. Therefore, I give ZSN Pro X 2/5 in personal preference.

Upgrade path

Should you get ZSN Pro X if …

• No. There are better options out there nowadays, even from KZ and CCA.

Where to go from ZSN Pro X if you want …

• all-rounder on a budget: Dunu Titan S
• all-rounder with a larger budget: Blessing 2 / Blessing 2 Dusk
• properly done warmth: Final Audio E3000 / E5000
• more transparent sound and soundstage: Final Audio A4000