Select comparisons
Custom Art FIBAE 5 ($999, reviewed here). A neutral-tuned hybrid monitor hovering near the kilobuck mark, its only similarity with X4 is the neutral midrange tuning, but even then its note weight is on the thinner side compared to X4’s natural tone. Both its bass (too close to neutral for my liking) and treble (too far from neutral to my liking) make FIBAE 5 both livelier and more coloured than X4, better suited to genres like classical music, while lacking the punch and dynamism of X4 with modern pop, indie and rock.
Campfire Audio Bonneville ($1,399, reviewed here). More bombastic than X4, with a powerful bass presentation that leads the way, and a treble that’s never shy to let you know it’s there. Despite having an extra BA and larger dynamic driver, Bonneville is technically close to X4. It’s got a deeper stage, sounding more holographic as a result, but all other technical metrics like resolution, imaging and separation are mostly on par. Like X4, Bonneville is an excellent all-rounder, though its tuning might still be too adventurous for some.
FIR Audio Xenon 6 ($3,899, reviewed here) and Radon 6 ($3,299, reviewed here). For the past few weeks, I’ve been listening to all three of these wonderful IEMs, and I swear if Xe6 and Rn6 had a baby, X4 would probably be it. X4 is still a youngling, by comparison, not quite reaching the same technical heights as the FIRs, sounding less refined and assured than its older, bolder cousins (as you’d expect for less than a third of the price).
From a tuning perspective, however, X4 shares traits from both. It has some of Xe6’s mid bass warmth and lower midrange fullness (not quite as much, but it’s there), combined with Rn6’s bass tautness, if not quite the same sub-bass extension. There’s no Kinetic Bass, but the tone, timbre and punch of X4’s bass are all there. It also shares the fuller note weight of the Frontiers, closer to Xe6, and some of Xe6’s treble sparkle – though nowhere near the same amount of detail. On the flipside, it’s gentler than Rn6’s occasionally strident treble, so makes for easier listening with certain albums.
Cable pairings
The one advantage of ordering X4 with a 2-pin connector is the ability to swap out the stock cable for third party alternatives. While there’s nothing inherently wrong with the stock cable, I found X4 to improve in certain areas with different cables.
Eletech Raphael ($499, reviewed here). I hear better refinement in the midrange, although the crispness from the treble – which is typically always well extended with Eletech cables – is still there. There’s also more resolution and texture in the bass, with a slight emphasis on midbass tilting the balance further from the sub-bass than it is with stock. Overall, Raphael is my favourite price-appropriate cable upgrade for X4, since it only costs half the price of X4 itself and so won’t break the bank.
PW Audio The 1950s ($2,199). You can buy two X4’s for the price of a single The 1950s cable, but then I’d argue that the performance improvement doesn’t make it as crazy an idea as it might seem on paper. While it’s no longer PW Audio’s flagship copper cable, The 1950s hasn’t lost any of its charm – or muscle. Bass is given a delicious quality boost, and the midrange is cleaned up, with a darker background adding to the sense of clarity. Imaging and staging is also improved, and treble is given a slight lift, adding to the sparkle and also infusing some extra air in the mix.
Cable swaps are not always widely appreciated, but X4 is quite the chameleon if you’re willing to experiment and have the means to do so. The biggest benefit, for me, is more refinement, especially in the mids, though as you’ve seen above, you don’t need the most expensive cable to make that happen.
Closing thoughts
To be perfectly honest, I wasn’t expecting to review Bellos Audio’s X4, but now that I have, I’m so glad I did. This is an IEM that’s supposedly not made for people like me, but rather for stage and studio professionals who specifically seek out and value the many refinements in fit and robustness it gives them.
It’s easy to see, then, why the X4 is catching on as one of the most versatile easy listening all-rounders money can buy right now. Not only is it relatively affordable, considering the inflated prices you’ll pay for IEMs with similar performance, but the tuning is just so good, it makes the simple joy of listening to music about as inviting as that sounds.
This shouldn’t come as a surprise; after all, I’ve heard through the grapevine that the Bellos brothers know a thing or two about tuning IEMs. In all seriousness, though, X4 is actually quite different to their normal fare, even though it shares some of its stablemates’ personality traits. While FIR’s Frontier Series is all about taking tuning risks and reaching new technical heights, Bellos Audio’s X4 plays it safe, with a sweet, relaxed tuning that’s I’d wager is almost impossible not to like.
Bellos Audio was created to find new solutions to old problems for stage and studio IEMs, and the X4 is a direct result of this project. From In-Ear Canals – which, if you ask me, is the single biggest breakthrough in custom IEM design in recent years – to 3D-printed shells with pre-assembled drivers, this is an IEM that breaks new ground, even before we start talking sound.
It’s not perfect, and on balance it still lags behind the very best IEMs I’ve heard when it comes to sheer technical performance, but it almost doesn’t matter when X4, like Goldilocks, just lends itself to lazily kicking back and enjoying track after track of naturally sweet music for hours on end.
I can’t speak for performing artists and audio engineers, but for me, as an audiophile and avid enthusiast, X4 has earned its place among far more illustrious company. Highly recommended.
Order your own X4 – or try out one of the other X-series IEMs – direct from Bellos Audio.
