Both headphones have the same 44mm diameter dynamic driver, although the driver on the Hi-X60 appears to be different and 5g heavier, assuming all components are the same between the two headphones.

I was also happy with how it sounds with my Hiby R3 Pro. However, I needed to almost max out my R3 Pro for the Hi-X55 to sound its best. In general, the Hi-X55 will need a nice detailed source to make it sound its best. The ATH-M60X and Hi-X60 are both studio monitors designed for studio mixing and both have very similar tuning, but with a big difference in overall performance.Hi-X55 are solid. Very nice combination of metal, plastic and pleather. They are not fancy by any means while they have this truly professional look. Work horses! That precision and snap continues elsewhere in the sonic range. The treble and midrange are clean, crisp and detailed, and everything is fairly even across the spectrum. However, there is a slight tendency towards brightness in the upper midrange; this brings voices to the fore, but doesn’t detract from the rest of the piece. It does mean, though, that you should take care with any partnering electronics, and avoid equipment that errs on the brighter side of things. The vocal range on the Hi-X60 is a bit recessed, wherein vocals are a bit farther behind but not too behind that it is overpowered by other elements. It still commands its presence without feeling drowned out. Although the vocals do not sit in the front, detail retrieval is still above average, with an acceptable amount of articulation of vocal textures of male and female vocals. I wasn’t expecting much difference in terms of the performance of both monitors. Mainly because the specs and the looks are practically identical, aside from the subtle weight and color differences. I couldn’t be more wrong. Both are designed for studio use but the presentation is quite different. Guitar strums on the Hi-X55 are also presented naturally. When I’m listening to the guitars, I can almost imagine the size of the guitar’s body and the way the guitarists are shifting their fingers through the fretboard.

Every voice, every instrument sits in the right place, just a little closer in the circle, closer and a touch warmer, fuller than with the K812.Highs - I've never been great at discerning high frequencies. These headphones are bright cans. With that comes detail and airiness, etc. but it can also lend itself to sibilance. I didn't find the highs to be as sibilant as the DT770s, so I'd say that's a win in my book. I don't have much to say about the highs, but feel free to ask me questions. At this price, there’s little to criticise when it comes to dynamic expression and low-frequency punch either. The Hi-X50 simply get on with the job with little fuss. They sound a little forward, and are more direct and less spacious compared with the over-ear Hi-X55, but beyond that the two share pretty much the same sonic signature, as would be expected by the similarity of design. Verdict I tried them with the single-ended output of the Schiit Magnius, which is known to have some issues with the single-ended output, and indeed the Hi-X55 revealed the shortcomings of the single-ended output of the Magnius. It exposes any of the flaws in your system, so feeding them through a good-quality DAC and a smoother amp is an absolute necessity. While I don’t quite see how the Hi-X55 has roots in previous AKG products that I’ve seen, the team’s experience seeps through the design, tuning, and refinement. Anyway, in short, X55 is harsh because it is designed to sound critical, or maybe brutal, toward mixes. I find it personally still quite well-tuned. And after my first day, I will say I get accustomed to its sound. Coming from Grado and Sennheiser, X55 really feels like a new paradigm for listening to music.