I purchased this after watching a lot of reviews, opinions, and posts on various websites. It seems right up my alley. A more exciting HD650? Sure. Basically as good as the HD660 at a fraction of the price? Why not? At $150, it's not like I'm buying a car or something. So I ordered one.
A bit of background. I have either used or owned the K7xx, the HD650, the HD600, the HD558s, HD598CS (closed back), and the Philips Fidelio X2. My comparisons are mostly to those since those are the frame of the reference that I have. I like my headphones relatively relaxing. I like stuff I can use all day. My daily drivers are the HD558s and HD598CS. The rest were either sold or were borrowed. Anyway, my observations below are based on the headphones I have previously owned. Obviously when I say the clarity is excellent, I don't mean compared to something like Stax lol, I mean compared to the stuff I've listened to before.
Also, I do not own a single amp/dac. This review comes from a completely un-amped experience.
Okay let's go.
The sound quality on these are impressive. Everything sounds quite clear. These headphones are fast and accurate. Faster music like metal sound fantastic and cluttered compositions like classical still manage to sound clear, airy, and uncluttered.
I'm a little sensitive to treble, so hearing everybody say that they were brighter than the HD650 made me a little nervous. Thankfully, these are in no way "bright" headphones. However, there is definitely no "Sennheiser veil" either. High hats and other treble-y noises are prominent in the music and very noticeable. They are in no way over-powering, though. I noticed the treble presence the most in metal music (the high hats and symbol crashes, mostly) and they sounded fantastic. They were there in the mix, loud enough to add to the musical experience, but in no way sharp, sibilant, or "too strong". This, in my opinion, is the perfect treble (which means it may not be enough for people who want exactly even treble or even strong treble). More treble than the 558s, 598CS, and 650s. It's about as much as the 600s. The K7xx had more treble, but it sits differently in the mix so it sounds like there's less but there isn't, if that makes sense. The K7xx and the 58x are just as good in the treble, but the 58x sounds better to me.
The mids are very present, but sit further back in the mix than I'm used to. This is definitely not the "thick midrange" of the 558s or the 598CS, but it's also not quite the same as the 650s or 600s either. It's full without being full. In other words, you don't miss any notes, but it sits in the mix in a way that makes the sound easier to digest. Think of it like an insulated blanket vs a full comforter. A comforter keeps you warm, but it's heavy, thick. An insulated blanket is much lighter and thinner, but it keeps you exactly as warm, and that's about what the midrange is like in these headphones. It's very much like the 600s to me. However, the 600s have a VERY sharp upper midrange (mostly noticeable with snare drums in some rap songs like Atmosphere's Sunshine). The 58x turns this sharpness down to a tolerable level, and thus I like the midrange in this headphone more than the 600s. Like the treble, it's basically perfect for me. Less full sounding than the cheaper Sennheisers, but better sounding and more in control than the 600s or 650s. The K7xx has a more recessed (but still very pleasant) midrange comparatively. The lack of that "too full" sound in the midrange also greatly contributes to this headphone's clarity.
This is a weird one for me. The 558s and 598CS actually have fairly powerful bass, but it's muddy. The 600 and 650 have clear bass, but not a ton of extension, and the K7xx has excellent bass extension but not a ton of volume. The 58x kind of meet all of these experiences in the middle. More clarity than the 558s and 598CS by a long shot, more extension than the 600 or 650, and more volume than the k7xx. These are NOT bass heavy cans by ANY stretch of the imagination. There is enough there to feel a bump, but it never takes control of a track (unless it's designed that way, like most Maroon 5 songs). Of all of the portions of the phone, this one is the easiest to explain. Good extension, good volume, never over-powering. Basically, perfect, from an objective standpoint, and not mine lol.
Outstanding. My test tracks for clarity include any Slipknot song, large band music (thing big band like the 1920's), classical compositions, and some video game and anime soundtracks. Anything with a ton of instruments and dynamic range (like Apocalypse Noctis on the Final Fantasy XV soundtrack has a huge, loud intro and then it tapers off to this sweet, quiet little strings section, that's what I consider to be dynamic range). The 58x handled it all perfectly. At no point did the sound just mash together into a giant blob, as was wont to happen with the cheaper Sennheiser cans. The 600s, 650s, and k7xx also have outstanding clarity and to be honest I'm not entirely certain which of the four (600, 650, k7xx, or 58x) has the best clarity, because they all present the music in a slightly different way. Suffice to say, in no song I listened to could I not pick out each individual instrument (or in the case of classical, set of instruments). Considering I paid $80 for the 558s (used, 5 years ago), and $80 for the 598CS (also used), the idea that these are less than twice the price is amazing to me.
There is not a ton of soundstage with the 58x. It reminds me a lot of the 600 and 650 in this regard. Everything has its place, but it's all pretty close together. You're not getting the ridiculously airy sound of the k7xx or the Fidelio X2 with these. You won't accidentally confuse these for speakers somewhere in the room. However, after conducting a couple of binaural tests, these things have the capacity to sound like real life and throw a noise really far away if they have to.
These have some serious clamping force, like basically the entire 58x/6xx range of Sennheiser cans. The ear cups are comprised of a cloth (velour?) covered foam and it's not memory foam. They're a little stiffer than I'm used to (especially after the mind-melting softness of the Fidelio X2 and the k7xx), but by no means uncomfortable. I bend the metal extenders out a little bit to lessen the impact on the sides of my face and the padding on top does its job admirably.
I may switch out some parts of this for others. For instance, I prefer the HD600 headband padding (four bumps > two long bumps, imho). Of course, eventually, when the pads wear down, I'll need to buy 660/650/600 pads to replace them and I guess there's a subtle difference between the 600/650 and the 58x/660 ear cups. We'll see when the time comes. In any case, these are definitely comfortable once you loosen the clamping force a little bit (unless you like headphones hugging your face like a terrified cartoon character or like, well, face huggers in Alien lol).
The good (pros):
1. They sound fantastic, even, and non-fatiguing. The 558s and 650s have an even more relaxing and non-fatiguing sound, but the 58x are more exciting overall to listen to.
2. Good bass extension without being obnoxious about it. Good treble extension without being awful about it.
3. The 3.5mm cable that comes with it is good for walking around with a phone in your pocket and probably good enough for laptop and desktop use for most people. I appreciate that because I am so tired of the 10ft cables Sennheiser includes with their stuff.
4. Surprisingly good efficiency. They sound more than loud enough on my laptop, desktop, and phone without need for an amp. I'm sure an amp would clean up the sound even more, but I'm not in a rush to get one. These are louder at a lower volume than my 50ohm 558s (on most songs).
5. Amazing price for these cans.
6. Repairable with HD600, 650, 660, etc parts if I ever need it. I may go with the 4 bump headband of the HD600s as I prefer them over the 650 style, which these have.
7. Lightweight which is nice for the long, long listening sessions I have planned for these things.
1. Slightly (and I mean slightly) hot in the upper midrange section like the rest of the 6xx series (you can see it in the frequency response chart in the 4-7kHz range). It's really only noticeable on a few songs, though, and it's not nearly as prominent or over-powering as the HD600, which is why I don't own those anymore. Really, I've only had a problem in a couple of poorly mastered rap songs where the snare drum just slaps you in the face for the whole song.
2. Clamp force is ridiculous, but that's a temporary and fixable thing.
3. Wish the pads were a little softer but they'll soften up over time so it's not a huge deal.
4. Wish the headband weren't glossy. Matte is the superior finish. Preference thing, though, and not a real complaint.
Keep in mind that all of my observations are completely un-amped on a Galaxy Note 9, an HP Omen laptop, and a desktop with a Ryzen 7 1700 (and a midrange motherboard). Additionally, my "audiophile (lulz)" experience is basically restricted to the headphones I listed earlier, so I can't tell you how this compares to something like the HD800, Stax, or basically any planar headphones. What I said above is strictly based on the sound quality and characteristics of what I've heard before.
I'm also sure you can get some changes in the audio by giving it some proper power, tube vs solid state, and whatnot. However, these get loud enough for me at around 50% volume on my Note 9 (sometimes louder if the track is generally quieter) and I honestly don't feel like additional accessories are necessary right now (but y'know, probably in the future). These headphones are accurate, fun, non-fatiguing, comfortable, and completely repairable. I'm very happy about these. They are worth every penny.
I picked up a Topping NX1s for like $35 on Amazon just to see what these sound like with an amp.
In short, there isn't much of a difference at low to medium volume. Maybe the bass gets a little stronger? Maybe? I might be stretching it just to say something lol.
However, where did I notice a significant difference is at higher volumes. At 90%+ volume on my Note 8, the 58x starts to get a little out of control. Like they aren't getting enough power to its sound signature. Bass gets a little boomy compared to the midrange and the treble dips a lot.
With the amp, the sound signature stays consistent all the way up to 100% volume. That's awesome, but it's also the only difference I noticed. It helps the headphone "hold it together" at higher volumes. Like I said earlier, I didn't notice any changes to the sound signature aside from maybe a bit of extra bass response.
100% is a little loud for me, so I likely won't use the amp a whole bunch as they sound fine at the 50% volume I usually listen at. I do plan to keep it though, just in case I want to jam out a little louder.