While I’m not the biggest believer of burn-in, there is no doubt in my mind that the RE-600 has undergone change in one way or another. Out of the box, the RE-600 sounded quite dry and their midrange was unnatural. While a lot of earphones sound the same out of the box or experience small changes relatively quickly, the RE-600 did require a lot of burn-in, around 200 hours before I noticed any changes at all. By the time I got around to the full review, my RE-600 had over 300-hours of burn-in and sounded perfectly natural and extended in either direction. I also rolled a few tips looking for a little extra low-end and found the Spinfits and Sony Hybrids to provide that little extra warmth. However, both also had a negative effect on the midrange so I ultimately stuck with the stock dual flange tips as they were the most linear and natural sounding to my ear.
The term balanced gets tossed around a lot in reviews but few earphones are described as being neutral. Because neutral is so similar yet so different to balanced; while I would call an earphone like the New Primacy or Campfire Andromeda balanced, they are most certainly not neutral in any way. And that’s because neutrality isn’t always ideal, balance enables room for sculpting and personalisation whereas neutral is thought to be derivative of a tool as was the original Etymotic ER4. But with neutrality comes many benefits, namely transparency, consistency and resolution. The RE-600 is almost ER4 neutral but with better sub-bass extension, a little more deep bass presence and a smoother high-end. This actually makes it very difficult to appreciate the RE-600 because they don’t leverage clarity and aggressive high-frequencies like the ER4 and Grado GR10E to justify being so lean. Instead, the RE-600 is smoother and more laid-back, how they can be so forward and laid-back at the same time escapes me, and though it provides an unorthodox listen, the RE-600 has all the technicality I could wish for.
They can sound anaemic on first listen, but one can quickly acclimatise to their sound, especially if you’re coming from an already leaner earphone. Their stunning transparency and great end to end extension also mean that they respond very well to eQ, and it was evidently a conscious choice on Hifiman’s behalf to make them sound this neutral and lean. I do feel that the RE-600 is actually slightly mid-forward though bass and treble never become overwhelmed in any way.
The RE-600 has a fantastic soundstage considering the size and nature of the earphones sound though the outstanding 1More Quad Driver possesses more space and separation while the Pinnacle P1 is wider in presentation. The RE-600 has a well-rounded presentation with very good width and depth but just average height; though few earphones around this price really excel in this regard. Imaging is the RE-600’s speciality, they are one of the best performers I’ve ever heard with regards to instrument placement and centre image at any price. When listening to Bigbang’s “Last Dance”, vocals were appropriately diffuse without sounding distant while guitar strums and atmospheric effects were all perfectly placed with exceptional layering and plenty of space. By comparison, the RE-400, Pinnacle P1 and even 1More Quad Driver all provided considerably vaguer responses. Separation is very impressive, not quite Quad Driver impressive, but easily on par with the Pinnacle and other similarly priced earphones despite the RE-600 being the most mid-forward. It’s the soundstage that really prevents the RE-600S V2 from sounding over forward and fatiguing, it is far superior to the Etymotic ER4 in terms of space while retaining that razor sharp imaging, making the RE-600S the endlessly more listenable daily earphone.
The RE-600S V2 is very neutral in the bass department with a slight emphasis on deep and sub-bass. They are completely devoid of flab or bloat and bass speed is comparable to any armature-based earphone. That being said, they also have a lot more sub-bass than the vast majority of armature earphones, even those costing many times more. Once adjusted to their lean low-end, I quickly realised that the RE-600S V2 isn’t missing out on any low-frequency information with great sub-bass reach and nice rumble. They don’t have the same bottomless bass response as the ie800 or larger dynamic driver earphones like the cheaper Fiio F5, but they do provide a nice sense of moving air when the track calls for it. Being as transparent as they are, bass really gets out of the way when not called for and the earphones can sound quite thin with certain material. On the flipside, the RE-600S V2 has the ability to sound very full and warm, once again, when the track calls for it. As a result, the RE-600S is not always the easiest earphone to listen to and they don’t sugar coat your music like a lot of earphones out there, but if you’re looking for fidelity, you will find plenty to love here.
Of course, isolated comments fine, but it’s in comparison to class leading earphones in different price ranges that the relative performance of the RE-600S V2 becomes apparent. From the outset, Hifiman’s highly awarded RE-400 presents as the most pertinent comparison and though the two don’t vary much in tuning, the quality of the RE-600’s sound has been universally improved. Within the low frequencies, the RE-600 is instantly more deep bass focused than the RE-400, though the RE-400 has more mid-bass, sounding fuller as a result. When listening to Red Hot Chilli Pepper’s “Soul to Squeeze”, bass notes on RE-600S had more of a sub-bass focus, bass had more depth while the RE-400 sounded slightly fuller and more punchy. Bass notes had more texture on the RE-600 despite having slightly less emphasis and bass resolution was appreciably improved. I also found comparison with the GR10E to be intriguing as both earphones pursue a similar sound yet the Grado has maintained its initial $400 asking price; so let’s see if that retained value translates to a similarly timeless audio performance. Being a single BA earphone, the GR10E lacks the bass depth and sub-bass fullness of the RE-600, although its single moving armature driver grants it with very impressive end to end extension. Listening to David Bowie’s “No Plan” revealed that the RE-600S manages more sub-bass solidity and a little more texture in the low-end. The GR10E had a punchier mid-bass performance that was still without a hint of bloat or flab; it was also admirably nimble and tactile, handily matching a lot of multi-armature earphones. The GR10E did have a little more bass definition though both resolved similar amounts of nuance and texture.
Hifiman has always impressed me with their midrange tuning, and its good to see that their expertise with open headphones has transitioned well to the in-ear form factor. It was actually within their midrange that the RE-600S drew parallels with the RE-400 and Grado GR10E with the RE-600S providing a nice middle ground between the warmer RE-400 and brighter Grado. The RE-600 unsurprisingly has more similar tuning to the RE-400 though subtle tweaks in all areas bring the tonality closer to neutral reference while improving upon resolution, transience and texture. The RE-600 is a slightly mid-forward earphone with very revealing and neutral bodied mid tones that makes the slightly thicker, warmer RE-400 sound lacking in resolution and detail. The RE-600 also has more midrange clarity partly due to their more forward presentation though they still don’t quite sound as glossy as the more sculpted earphones around this price like the 1More Quad Driver. The RE-600 is also an exceptionally coherent earphone, more so than the RE-400 due to its superior staging performance, with improved vocal layering, background detail and separation. The RE-600 is very detailed despite not being particularly aggressive, with similar retrieval to class leaders like the Pinnacle P1.
But coming back to the RE-600’s initial $400 asking price and comparison is not quite so single sided. While they comfortably compare to the very best $200 earphones out at present, the RE-600S V2 still lacks that extra layer of technicality possessed by more expensive earphones. To reinforce my point, I’ll draw comparison back to the $400 Grado GR10E, released around the same time. Immediately, the GR10E provides a surprisingly balanced listen for a Grado product; it is definitely one of my favourites from the company. The Grado maintains tinges of that signature Grado sound with a slightly brighter tonal tilt and a plethora of midrange detail, definition and resolution. Though the RE-600 is a very clear and resolving earphones, the GR10E is clearer yet and slightly more resolving at the cost of sounding slightly thin and raspy throughout. The RE-600S sounds more natural with more body to vocals but also less overall clarity. And though they are more accurate in this regard, the hyper clear GR10E really flatters female vocals and accentuates their sublime resolution and detail retrieval. On the contrary, the more linear RE-600 is more consistent with most instruments and male vocals do tend to sit slightly behind on the GR10E, where they are more balanced on the RE-600. The GR10E is also a little dry in the lower mids while the RE-600 proves to be more natural and coherent. Considering that I prefer brighter earphones, it’s no surprise that I bias the GR10E though, at their reduced price, the RE-600S represents terrific value with only slight compromise on quality while holding some advantages in tuning.
Despite their lean bass response and linear midrange, the most polarising aspect of the RE-600S V2 will likely be their treble tuning. As aforementioned, most lean, neutrally tuned earphones like this tend to have aggressive treble responses that provide awesome clarity and detail uninterrupted by their leaner low-end. However, the RE-600S V2, despite their new silver plated cable, is instead quite smooth and laid-back with slight roll-off at the very top truncating some high notes. So like the Fiio F5, they do lack that instant wow-factor though longer term, they prove to be just as revealing while being vastly less fatiguing; As much as I love the GR10E, I wouldn’t listen to them all day for instance.
When listening to Radiohead’s “High and Dry”, treble notes on the RE-600S were notably more resolving than the RE-400 though the RE-400 does have a little extra emphasis that the RE-600 does not possess, making the RE-400 sound more vivid and dynamic. That being said, the RE-600 doesn’t sound particularly dark due to their great detailing and resolution and the RE-400 does sound more granular by comparison. The Grado’s are interesting in that they create that vivid and endlessly revealing treble response without succumbing to grain or harshness. This was most evident when booting up Nirvana’s “Lithium”, a very treble heavy song which can sound downright crunchy on some earphones, especially those with any kind of middle treble emphasis; fortunately for me, neither the RE-600S nor the GR10E provided an ear-splitting rendition. The GR10E immediately impressed with fantastic extension, detail retrieval and air. The RE-600S was a little rolled off in the high-end, especially audible in comparison to the GR10E, with treble notes being pushed back a little by comparison and higher details were less crisp and aggressive in their presentation. The high end on the RE-600 is definitely on the more laid-back side despite the upper midrange being quite aggressively detailed whilst the GR10E is quite aggressive all the way through. As a result, the RE-600S is smoother throughout though the GR10E is more separated and considerably more open.
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