7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 20

7Hz Salnotes Zero vs QKZ x HBB Review

7Hz Salnotes Zero

The Salnotes Zero is the second IEM after Dioko from the sub-brand of 7Hz. It comes with a 10mm dynamic driver with a metal composite diaphragm, utilizing technology exclusively developed by 7Hz. The metallic composite diaphragm used in this product is made of high-quality materials.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 7

7Hz Salnotes Zero is housed in an environment-friendly plastic shell with a stainless steel faceplate. It comes with a detachable cable. The cable is made of 4 core high purity Oxygen Free Copper in a parallel structure while each core is made of 19 x 0.08 wires.


  • Driver: 10mm dynamic driver
  • Impedance: 32ohm
  • Sensitivity: 108dB
  • Frequency response range: 10-20000Hz
  • Price: $19.99


The newly launched earphone from QKZ is a collaboration with Youtuber HBB “Bad Guy Good Audio Reviews”. QKZ acoustic engineers eliminated ordinary diaphragms and eventually selected a 10mm Titanium-Coated Diaphragm for this model. The IEM also has a new enhanced high-intensity magnetic circuit that improves the bass performance.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 8

QKZ x HBB comes in a clear resin shell with a CNC-processed aluminum faceplate. It’s definitely one of the most good-looking budget IEMs on the market with a very good fit and design.


  • Driver: 10mm dynamic driver
  • Frequency range: 20Hz-20kHz
  • Sensitivity: 115dB
  • Impedance: 22 ohm±10%
  • Price: $19.99

I would like to thank Linsoul for providing me with the review samples of  7Hz Salnotes Zero and QKZ x HBB.

You should treat this review as the subjective impressions of an audio geek rather than an “objective truth” about the IEM. Your experience with any IEM would change depending on your DAC/AMP, music library, ear tips, and listening volume.

7Hz Salnotes Zero Sound

7Hz Salnotes Zero FR Graph e1667129833665

The bass is elevated slightly above neutral in quantity. There’s a good blend of slam and thump that gives the bass notes a nice natural note weight. In a technical sense, Zero’s low-end performance is an integral part of the overall delivery. It extends well enough to provide ample sub-bass power and rumble when necessary.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 19

Zero’s midrange is tuned for naturalness over clarity. It’s articulated and nuanced but has a pleasing warm undertone. As a result, instrument and vocal notes have a neutral note timbre that’s organic and transparent. There’s ample clarity in the midrange but the focus is on musicality and tone. Despite that, however, this midrange performs well in a technical sense too, with good instrument separation and spacing.

Vocals are placed up front and rise clearly above everything else. This makes them engaging but leaves enough space around the center image for other layers of sound. The tone of vocals and instruments sounds just right, neither too thin nor thick. There’s a subtle lift in the upper mids that adds presence and vitality without harshness.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 18

Most of the treble focus is on the lower range. It sits just behind the upper midrange in terms of forwardness and is fairly smooth. Treble tuning has a hint of warmth giving it a natural tone. And despite its smoothness, the treble is adept at revealing details. Not by being bold and upfront in its presentation but simply as a result of its evenness. It might not be the most glamorous or sparkly of trebles but it’s easy on the ears and free of sharpness. Treble blends naturally because of its coherency and finds an ideal balance relative to the bass and mids.

7Hz Zero’s tone and timbre make this budget earphone stand out in the crowded budget space. The naturalness and tonal accuracy found here are rare for something in this price range.

QKZ x HBB Sound

QKZ x HBB FR Graph

The QKZ x HBB’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. QKZ x HBB’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.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 11

QKZ x HBB has 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 lower-register instrument 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.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 9

QKZ x HBB has a good level of detail. 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. The treble tone is slightly warm and smooth. You won’t hear any sibilance either. The QKZ x HBB’s treble is boosted enough to be exciting without crossing the line into sharpness.


7Hz Zero vs Moondrop Chu

7Hz Zero vs Moondrop Chu

Moondrop Chu is the pioneer in the $20 budget IEM wars. It is easily the new benchmark IEM as the sound performance goes for this kind of tuning. It might also be the most modded IEM for a detachable cable. But still many find it bass-lacking and also slightly brighter for their taste. 7Hz Zero fixes both problems on the paper (and in the ear) and gets the crown as the new king.



I had to include the KZ ESX and you know why if you look at the graph. And to be honest I like the ESX more than the QKZ as it can manage to balance all frequencies better for my taste. Although the bass level is still higher for my liking, more elevated upper mids, and treble help the end sound signature be more enjoyable.

7Hz Zero vs QKZ x HBB vs KZ ESX vs Moondrop Chu Review 6


7Hz Zero vs QKZ x HBB

As you can see from the latest graph these IEMs have very different sound signatures. QKZ being bass-forward, 7Hz Zero is on the balanced side having a better extension on the upper mids and treble. So it shouldn’t be hard which one to choose depending on your taste. Both do a very good job for their targetted audiences. If you ask me though the 7Hz is the best all-rounder IEM on the market right now, for $20, even for under the $50 price range.

Would love your thoughts, please comment.x