Performance

HiFiMAN's RE-400 design definitely pushed the envelope in terms of how well a set of $99 in-ears can sound. The RE-600s are four times as expensive, and some of the deficits with the RE-400s, which we reviewed not long ago, have been addressed and fixed with the RE-600s. The RE-600s ship with a more extensive bundle, and a new copper/silver cable made specifically for HiFiMAN products is used. The driver inside the RE-600s has also gotten some kind of new treatment, but information on what it entails is scarce.

The technology in the RE-600s has definitely been beefed up. The two most important aspects are probably the new cable and the titanium diaphragm's improved surface characteristics. The cable is now a copper/silver hybrid. How the cable is manufactured is unknown, as it is only made for HiFiMAN. The new coat on the titanium diaphragm is also a mystery, but it supposedly controls the way sound disperses in front of the unit.

The time and money spent on perfecting the driver has definitely influenced performance positively, when directly comparing the RE-400s to the 600s, volume matched. We started our testing off by hooking these in-ears up to our JDSLabs O2+ODAC with 1x gain, putting them through our usual test records. The RE-600s are definitely a honed version of the RE-400s. The basic qualities are carried over, as you would expect of two relatively similar designs, but a lot of small things have been perfected to a degree that may even warrant the quadrupled price. The RE-600s have an amazing representation of the sound stage, one you generally only get by shelling out big bucks for in-ears like the UE IERMs and PRMs. Whether this is due to the coating or cable, or a multitude of small tweaks, is unknown, but it really is a remarkable difference in sound quality.

Like the RE-400s, the RE-600s are very natural to listen to, and sibilance free. The bass is a bit more pronounced on the RE-600s, which is a good thing coming from the RE-400s. Compared to the UE900s, the RE-600s have less bass, but it is better controlled throughout and sounds more natural. Natural is probably the keyword when it comes to describing the sound of the RE-600s. Swapping back and forth between the RE-600s and our benchmark, the Westone 4R in-ears, it is clear that the RE-600s are smoother sounding but still very detailed. The sound stage of the RE-600s is in a different league than that of the 4Rs, but the bass is more taught and extends further on the Westone 4Rs. Treble on the RE-600s is less intense than on the RE-400s, the W4Rs, and UE900s. The RE-600s sound a little on the soft side here without losing any detail. They do not share the bright signature that HiFiMAN had with their RE-0s and RE-272s.

The sound stage of the RE-600s is only rivaled by the pricey UE IERMs which are not quite as musical as the RE-600s. These new in-ears from HiFiMAN are the most entertaining universal in-ears I have heard to date, out-performing even the Westone 4Rs which have served as our benchmark in-ears for quite some time. The projection of space and positioning of instruments is totally clear and coherent. That, combined with a detail level that is very close to the Westone 4Rs, makes the RE-600s winners.

Getting the RE-600s to sound their absolute best meant powering them from our JDSLabs O2+ODAC system. The sheer amount of tips from HiFiMAN does not make up for a well-constructed set, and hybrid tips clearly outperformed HiFiMAN's included offering of tips.