Aside from the naming problem, the RE-ZERO is an awesome addition to Hifiman’s RE line world. Hadi had written a fairly in-depth review comparing the RE-0 to the Phonak and ER4, titled “Detail Experts“. One thing that stuck with me from that review is how the RE-0 is “akin to looking at a clear pond”. And rightly so, the RE-0’s unique “clear pond” sound impresses me more than anything else. Compared to any iem at any budget, nothing else really has a “clear pond”-like sound like the RE-0. I’m not saying that more expensive IEMs can’t match the RE-0’s transparency, but the RE-0’s presentation is very unique and unlike anything else in any other IEMs.
Technicalities wise, most decent balanced armature drivers will give faster transients, and a better separation than the RE-0. The RE-0 yet is special in that somehow it presents a laid back sound yet with superb clarity of the music. Although the transients may not match balanced armature IEMs, the RE-0 manages to separates instruments fairly well. The tonal balance of the RE-0 reminds me a lot of the HE5LE orthodynamic with the grill cloth removed. The sound is generally dark, but within that dark landscape, the treble detail emerges with a brilliant sense of clarity. There is little midrange and bass body, which very like the HE5LE without the grill cloth.
After all those praises for the RE-0, I have to explain why the RE-ZERO is an improvement on the RE-0 concept. Despite the brilliant and unique sound, the RE-0’s frequency balance is not the best for music listening. The RE-0 would be fine for instrumental and classical music, but with a more mainstream Pop or Rock music with vocals, the the RE-0 doesn’t quite hit the spot. What’s needed is mostly a bump in the midrange areas to add some intimacy in the music. This is precisely what you find in the RE-ZERO.
The RE-ZERO takes the basic RE-0 sound and bumps the lower treble to upper mid to be more forward. That makes a BIG difference when you’re listening to music with any type of vocals. If the RE-0 gives a more wide-panned presentation, the RE-ZERO is far more focused. The RE-0 will give me the impression of a more spacious soundstage, but without a focus in that soundstage. It’s like a big auditorium where all the instrumenst are placed wide apart, but without a lead vocal to define a center point. The RE-ZERO, narrows down on that hall, making it sound more like a small coffee shop jazz performance, but with a much better focus on the lead vocal. With the RE-ZERO, the presence on the vocal is very spot on. On lower listening volume, the RE-ZERO may have an impression of a narrower soundstage, mainly due to the more forward midrange. But when the volume is turned higher, I think the soundstage size between the two is roughly the same.
Drawing from an analogy from the full size headphone, the RE-ZERO is like a stock Grado SR60, where the RE-0 is closer to the same SR-60 with jumbo pads in exchange of the stock comfies. Although the RE-ZERO is not exactly a Grado SR-60, but it does have a lot of similar character with the famous forward sounding Grados.