INTRODUCTION

Disclaimer: the Celest Relentless were sent to me by HiFiGO so that I could write an honest review. This review represents my personal opinion on the set, it isn’t a promotional or paid content and I don’t get any revenue from the sales of this product. At the time of the review, the Celest Relentless were on sale for $169.99 at HiFiGO$.

TECHNICAL SPECIFICATIONS

• Driver Configuration → 1DD + 6BA
• Impedance → 27 Ω
• Sensitivity → 105 dB
• Frequency Response Range → 20Hz-20kHz
• Cable → 5N copper silver-plated with 0.72mm 2-PIN connectors
• Plug Type → Modular plug: straight gold plated 3.5mm or 4.4 mm jack connector

PACKAGING

• The Celest Relentless
• The detachable cable with modular plug (so you can use either the 3.5mm jack or the 4.4mm jack)
• 3 + 3 + 2 pairs of foam tips (S,M)
• A storage bag
• A small cleaning/brushing tool
• User manual

DESIGN, BUILD QUALITY, COMFORT AND ISOLATION

CABLE

SOUND

• DAC: Topping E30
• AMP: Topping L30, Fiio A3
• Mobile phones: Samsung Galaxy S7 Edge, Xiaomi Mi A3, Samsung Galaxy S23 Ultra
• Moondrop May’s DSP cable with PEQ=0
• Dongle: Apple Type-C dongle, Fosi DS2
• Portable DAPs: Benjie S8/AGPTEK M30B
• Other sources: Presonus AudioBox iONE, Elgato Wave XLR, KZ AZ10

• Lows The sub-bass is controlled but it doesn’t rumble a lot: it’s a very clean sub-bass that won’t probably suit the average basshead’s tastes, but every other listener will not find it lacking. The focus is on the midbass, even though this is not super emphasized either: it has good textures, good punch and nice speed, but the combination between the controlled sub-bass and the emphasized treble makes it a bit less forward than it looks on graphs. Overall it’s a well done low-end for most genres, but those looking for the most punchy and full bodied bass out there will probably need to keep searching.
• Mids The mids are recessed, so those who are on the market for a mid-centric IEM should probably look elsewhere. The leaner-than-average midbass sometimes struggles to give more warmth and depth to male vocals, although most of the time they still sound nice (yet not really “natural”). The upper midrange is instead forward (at the right point) and somewhat intense, with energetic female vocals and rich violins/electric guitar notes, even though some episodes of sibilance may occur if the tracks are prone to that (this is because of the combination between the upper midrange glare, a slight dip and then a treble boost). The instruments are generally well separated, the layering is good and it really seems like the Relentless are not afraid of busy and crowded tracks, except for some cases.
• Highs The highs are bright and pack a lot of details, and the treble emphasis provides for a very open sound even though this also means that the Relentless should be avoided by those who are sensitive to treble. For sure, this is one of the IEMs that shine in the treble extension under 200$ (hands down) even though for some genres this may also be a hit or miss because of some particular sounds (i.e. if you listen to a lot of metal, some cymbals may be somewhat aggressive for prolonged use) and for a touch of BA timbre.

• Celest 221 Vocal Eartips (black): more emphasized treble, airier vocals and instruments, more sibilance
• Celest 608 Balanced (Red): more balanced, a bit less airy and slightly bassier but less fatiguing than the 221
• Foam tips: best balance between treble, bass impact and vocals and there is also less sibilance than on 608 and 221. Probably the best choice of the set.

Some comparisons:

Price is quite different yet both are hybrids placed between 100$ and 200$. The Relentless have a more robust and more textured the low-end (especially in the midbass region), whereas the EM6L have a richer midrange and more natural male vocals; female vocals, instead, sound more detailed and energetic on the Relentless yet a bit more natural and intimate on the EM6L. Both are kinda bright on top but the treble extension is better on the Relentless, even though the EM6L provide for a slightly smoother transition between the upper midrange and the lower midrange (with less occasions of sibilance). The timbre is nice on both but the EM6L sound a bit more natural, while the Relentless are less accurate from a timbrical perspective yet more fun and technical to listen to, with slightly better instrument separation and a more expansive soundstage. The imaging is not that different and the EM6L compete pretty well in this regard, even though the Relentless have more space to place everything properly and feels more “holographic”. When it comes to the build quality, accessories, cable and isolation, it’s an easy win for the Relentless, even though the smaller size of the EM6L may be better for some people out there.

Different driver configuration yet same company and similar price bracket: ok, let’s do it. The Relentless are brighter but they somehow feel less “thin” in the treble and sound more appealing and “correct” from a timbrical standpoint. In fact, the sub-bass extension is better on the Relentless and provides for a fuller and more engaging sound. The midbass is very good on both sets but the Relentless have better bass textures and better body, whereas the Phoenixcall compete with slightly faster transients when it comes to rapid basslines. The midrange is recessed on both sets but the Relentless do better in terms of vocals: the fuller low-end makes sure that male vocals don’t disappear and the smoother upper midrange emphasis gives more body and energy to female vocals (they sounded thinner and less natural on the Phoenixcall due to the earlier emphasis followed by a dip). The detail retrieval is very good on both sets too, but the Relentless are more proficient and pack a better treble extension (they also cost more, so it was expected). Soundstage is wider and deeper on the Relentless, whereas the height is similar. Imaging is better on the Relentless. The Relentless come with a slightly more versatile cable, but when it comes to build quality, isolation and comfort, they are comparable (even though the smaller shells of the Phoenixcall will appeal to more people).

Not really fair to compare a hybrid setup with a single DD set, but let’s try anyway. In terms of timbre/tonality, bass body/depth and vocals, there’s no competition: the EA1000 just sound like a more mature set. From a technical perspective, though, the Relentless compete quite well: the sub-bass has better extension, the bass is very speedy and it’s well textured (yet not as full bodied as on the EA1000), there’s lots of detail, the treble extension is very good (eveN though slightly less natural than on the EA1000) and both imaging and soundstage are slightly more clinical than on the EA1000. It’s unfair to compare these since the EA1000 avoid any incoherence that could come from the usage of different drivers, but it’s also true that the Relentless is not getting completely destroyed (which is good news). I would still pick the EA1000 hands down (it’s a more natural set with much better bass quality, richer mids and they also have that effortless way to reproduce every track correctly) but the Relentless really show Celest’s ability to keep up with proficient driver implementations. Anyways, the target is slightly different: those who want a single DD IEM will still pick a single DD IEM and those who search for a hybrid will only want that. When it comes to cable, accessories and isolation, the Relentless win hands down, whereas the EA1000 look like a slightly more premium set and come in a smaller-sized shell.

Final Thoughts