Bellos Audio X4 Review

Bellos Audio X4 Review by MajorHiFi

Bellos Audio is a new name for MajorHiFi, which is always an exciting prospect. What I have are their flagship custom IEMs, the X4. We’ve reviewed a few IEMs from their sister brand Fir Audio, so I’m expecting a similar standard of quality. Can the X4 reach flagship levels for a thousand-dollar IEM?

Bellos Audio X4 items

What You Get

  • X4 IEMs
  • RCX Cable
  • Metal carrying case
  • 3 pairs of silicone ear tips
  • 3 pairs of foam ear tips
  • Cleaning tool

Bellos Audio X4 single

Look & Feel

The X4 uses a 3D printed shell with a matte finish. There aren’t a ton of IEMs that have the same feel as the material used here, and it makes the X4 feel super durable. Aesthetically, the X4 looks like something you might grab out of a toolbox, with its bolts, black shell, and silver logo. The ear pieces are quite small too, offering a less cumbersome fit in theory. It’s not the size of the housing that causes issue for me though, it’s the seal. No matter what ear tips I used, the X4 popped out more than any other pair of IEMs I’ve tried recently. Eventually you can get the housing to sit in a comfortable enough place, but you have to work with it.

Bellos Audio X4 cable


The X4 has a hybrid driver configuration made up of one dynamic driver and three balanced armatures. It incorporates a four-way crossover helps organize the signal, while the special ATOM venting system helps vent harmful air pressure and also expands the soundstage.

Bellos Audio X4 pair


Sometimes pro IEMs like the X4 can have wide, but linear soundstages that come across like a flat plain of sound. The X4 doesn’t have that kind of imaging for the most part, but you can tell how strict the headspace is with busy tracks. When the X4 is dealing with tracks that have a ton of sound elements, the soundstage and imaging have an organized but surface level presentation that adheres to accurate stereo positioning. Each instrument feels specifically placed in the sound spectrum, stretching out the stereo signal around you mimicking studio monitors. This is as immersive as the X4 is going to get with its imaging, but it’s a completely believable representation of sound. At times, I was gripped by the X4’s realism and large wingspan that has enough wrap around to add some sense of dimension to the sound.

Low End

This bass aims to be enjoyed by everybody. It’s timbre reflects a certain weight and warmth that bass heads will love, while also exhibiting great clarity and tonal balance. Bass instruments have an engaging body of tone that gives each note a satisfying groove. There’s also restraint shown with how the bass of the X4 handles its resonance. The X4 never comes close to being bloated or overblown. Everything about the low end timbre, from the sub-bass to the mid-bass feels gratifying and realistic.


The midrange frequencies are perfectly even and easy to localize. Nothing ever gets bogged down in a hazy fog of low-mid extension. Every instrument exists in its own space and never gets relegated toward the background. At its best, the X4 can feature some very lush details, enhanced by the extended separation in the soundstage that brings more identity to the timbre. The notes are smooth, and offer enough precision without having significant attack to the them. It’s a very natural presentation, with enhanced vocals that have a crisp underline for extra definition.


In terms of loudness, the highs only take a slight step back but still share a good amount of presence in the sound signature. There’s a slight peak in the mid-treble that gives a bright timbre to some vocals and instruments. It adds some slight sparkle to sound elements, which adds character, and it still makes the highs easy to digest.


It’s tough to not be impressed by the sound of these IEMs at this price. The X4 feels like what I’ve been hearing from Fir Audio, and it makes sense that the X4 would be the top level of what Bellos Audio is capable of. The fit is a bit hard to work with, but when you start listening to the X4’s weighty bass notes and midrange clarity the experience is very worth it for the price.

Pros Cons
  • Wide soundstage
  • Pronounced bass notes
  • Midrange clarity
  • Durable matte design
  • Great cable
  • Not the best seal
  • Some high-end brightness 

The Bellos Audio X4 is available here.

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Alex S. is a sound designer and voice-over artist who has worked in film, commercials, and podcasts. He loves horror movies and emo music.