Great sounding phones, a bargain at the price
Earlier this year I bought a pair of the Sennheiser HD58x and liked them a lot. I also have a pair of the Koss ESP/95x which are excellent but have fit and comfort issues - and are not at all portable. I had been curious about the HiFiMan planars for a while, and I still needed a second pair of "portable" phones for mixing/monitoring, so when they went on sale I decided to buy a pair of HE4xx and give them a try. The price was right, and the general trend of the reviews was hopeful. Plus, there is always the free return option, so really not much to lose.
I did note that there were some people who had issues with the adjustable slider and its attachment to the headband. Looking closely at the construction, though, I was confident I could repair them if breakage occurred; everything is metal except for the adjustable slider casing and it can be easily replaced with a 3D printed part. The other concerns seemed to be the pads, heat accumulation, and the weight. I have found that I like velour pads a lot; they seat well and don't slide around. The heat could only be assessed by wearing them for a while. The weight - well, that would depend strongly on the distribution and comfort of the fit when wearing them.
I needn't have worried - the pads are very comfortable, much like the HD58x pads despite the hybrid construction. They fit nicely over my ears without covering half of my face, and seal well (possibly a side effect of the hybrid build). The headband holds the phones firmly but without excessive pressure. The weight: they definitely weigh more than than the HD58x but they don't feel heavy or unbalanced, nor do they want to slide off like the Koss did before I modified them. In fact, while searching online for some details to add to my review I more or less forgot I was wearing them for about an hour. In that respect they're quite good and I see no problems. Next was the concern about heat retention due to the lack of airflow. In the hour I was wearing them, I barely noticed a slight warming. I keep my office comfortably warm already, and I felt no desire to pull them off in order to cool down. When I did remove them for other reasons, I was ready to put them right back on again if needed. No sweat - literally. You may find them more bothersome, but for me they were fine.
Now, what about the sound? I actually own no fewer than four different brands of speakers with planar drivers, so I have heard different designs and applications over a period of years. I think there are some things that planars seem to do well, though I wouldn't say there's necessarily a "signature" that they share. A properly designed planar does seem to be able to provide good audibility of musical detail; whether that's a native characteristic of its design/construction or just a consequence of flat frequency response and low distortion, it's hard for me to say. I've heard good dynamic or "cone" drivers which also have a detailed and seamless sound, though it does seem more rare. Maybe it's just easier to build a planar driver which gives accurate reproduction of a signal; or maybe it's a result of the designer having better understanding of the electrical characteristics of the device when constructing it. Maybe the poor planar drivers just never make it to market. Or it could be that something about my preference in sound lines up with what the planars do.
No matter the reasons, I've liked pretty much all the conventional planars I've ever heard. From the sadly-defunct Monsoon drivers, to the Magneplanars, to the Infinity EMITs and others, they've all had something interesting and captivating about them. And the HE4xx is, happily, also in this category. It has the good reproduction of detail that I'd hoped for, an extended frequency response and the ability to play rather louder than I'll ever need, when I give it enough power. That's the only real concern I have, and will discuss it later.
While most measurements (and some reviews) indicate that the HE4xx is somewhat anemic in bass response, mine seem to go pretty deep. I have tried using Oratory1990's EQ profile as well as using no EQ at all; even without the bass boost there is plenty of low end. With it, there can be almost too much on some recordings. I think the seal over my ears is so good that the bass hardly cancels at all, leading to minimal roll-off. At any rate, I find that I need little or no bass EQ to get satisfying low end from this headphone; I've ended up lowering the gain on Oratory1990's bass shelf filter by a few dB so that the balance is a little better to my ears. I have also set the shelving frequency rather lower than suggested to minimize gain in the 100-200 Hz region which otherwise tends to muddy the bass.
Again, without EQ the bass is decent in terms of balance, though it may roll off at a higher frequency than you prefer. One thing that seems consistent, though it may be due to the shape of the bass response, is that these phones appear to have a lot of impact in the lows. It doesn't seem related to the EQ profile; once I EQed my HD58x it had a similar low end but not as much 'punch' or whatever you would call it. Whatever the reason, it's what I would call euphonic, and enjoyable. Bass drum and other instruments with significant low frequency transients really shine with these phones, especially after EQ. Acoustic bass and brass such as trombone have a lot of apparent detail in the bottom register. Pipe organ can be intense - I have a few reference recordings with some genuine 16 Hz pedal (verified with an RTA) and there's no question when it comes through.
The mids, without EQ, tend to be a little forward, though not obnoxiously so. A little tweaking (again, using Oratory1990's recommended curve) helps vocals sound more natural. This is a frequency range which unfortunately varies from listener to listener due to the shape of the ear's pinna and the phone's interaction with it, so others may find the stock performance just fine. The highs seem pretty clear and clean with or without EQ, though they seem also to be revealing of sibilance and other artifacts in the recordings. The recommended EQ, again, does a pretty good job of making the highs a little more balanced. You may find it's not needed; I was able to enjoy listening to the phones without any EQ, though they seem to sound less detailed and balanced. Honestly, I don't think there's a headphone on the market that won't improve with carefully tailored EQ. Some, of course, won't take EQ very well, particularly if it's an added boost. The HE4xx has no problems there, within reason.
I've been sitting here listening to some electric and acoustic recordings while writing this review, and it's been an overall very pleasant experience. I can hear all the inner details of the music, and find that I don't have to turn the volume up to do so. While some headphones and speakers invite turning them way up (and encouraging ear-damaging levels), these phones will tolerate it but it's simply not necessary. I suspect this has to do with how faithfully the mids and highs are rendered; a transducer with peaks or resonances will irritate the listener and cause a feeling that it's already "too loud" while a headphone with dips in the response may need to be turned up a lot in order to hear the musical details. The HE4xx sits somewhere in the middle, which I think is good. For the sake of consistency, I've also listened to boring pink noise, and confirmed that with the EQ settings I've chosen no frequency band in particular seems to be emphasized or reduced when listening. Note that Oratory1990 himself states that you may prefer small changes to his recommended EQ, so I don't feel I've subverted his EQ settings by tweaking the bass level.
While listening to the same music, I've switched back and forth with my Koss ESP-95x, and I think what little difference in quality there is may be due mainly to the way they are EQed. The Koss seems to respond less well to bass boost, unfortunately (at some point adding bass does nothing except overdrive the transducer), which makes it sound a little 'thin' by comparison. It may largely be due to the Koss' less satisfactory head seal and consequent bass loss. Surprisingly, the highs are pretty good on both phones (full disclosure: my hearing is not so good above 13k but measurements seem to show the HE4xx to have very extended highs just like the Koss) and the mids are a toss-up - again, this is partly dependent on the individual listener's ears. Some EQ might be warranted, and I have tweaked the response on all my phones accordingly; but the recommended EQ is pretty close. I really am surprised that the HE4xx holds up so well against an electrostatic, especially an expensive one which I am so impressed with. It goes to show that EQ can narrow the gap between otherwise well-made headphones. They are easy and satisfying to listen to, though, and don't give much away to the Koss.
As a more price-competitive comparison, I also tried my Oratory1990 EQed HD58x. Without EQ, these phones have a fairly different signature, but with EQ they also came close to each other. There was a little more bass extension than the EQed HE4xx, and the highs seemed a bit more aggressive but that may just have been the fact that the EQ does not attempt to flatten the extreme highs (above 10k). These attributes may not have been entirely due to EQ differences between the phones, though; those are the two frequency areas where the seal and positioning of the earpieces have a significant effect on the subjective sound. The way they are currently set up, I still like the HE4xx better, but it wasn't as big a difference as I had expected. I may revisit the HD58x later to see if I can close the gap. Incidentally, I've seen some comments asserting that the Oratory1990 EQ for the HD58x is based on an outlier sample of the phones and it doesn't give good results. The fact that his settings make my HD58x sound quite a lot like the EQed HE4xx tells me that they're in fact doing what they are supposed to. Honestly, I could listen to either pair and be pretty happy.
One thing which is clear, though: no matter whether you use EQ or not, these phones are relatively inefficient - they need a healthy amount of power. I originally hooked them up to one of my smaller headphone amps (about 150 mW @ 32Ω) and they sounded good but any attempt to raise the volume beyond a modest level resulted in noticeable clipping on loud bass transients. Substituting a better amp capable of about 1W helped enormously; in fact, it will play much louder than I need, and very cleanly. So do not expect to drive these phones well with a typical smartphone or a computer having a wimpy analog output. A good headphone amp is not that expensive; you can get something audibly transparent for well under $100 and it will probably do a much better job than some random receiver with pad resistors in series with the output. Right now I'm using a SMSL sAp-II and it's fine. If you don't have a good headphone amp you may be disappointed with the amount of (clean) volume you can get out of these.
Second, don't be afraid to EQ any headphone. It's silly to think that after all the recording, EQing and mastering your music has gone through on its way to you, it's cheating to polish the signal a little and make the listening experience more enjoyable. Believe it or not, every producer has their own take on what a recording should sound like, and many of them actually use very bright and somewhat inaccurate monitors/headphones so they can hear all the flaws in the mixdown. If you're not inducing excessive distortion or damaging the phones, EQ is quite handy to achieve a better match for your music and hearing. Not to mention, to take advantage of the qualities that you bought the phones for in the first place. Being able to get my three headphones to sound as much alike as I did without trying to do so was a bit of a revelation; I don't regret purchasing any of them, and there are still times when I'd choose one over the others. The differences in sound after EQ are not great, but they still have their own comfort and long term listening qualities - very important when you clamp a pair of speakers on your head for a period of time.
Overall, I think the HE4xx are great headphones for me, comfortable and revealing of detail. If they hold together, I'll be listening to them a lot. But that's true of any of my preferred phones. They're a superb value for the money, as are the HD58x.
Update 2/2021: No mechanical problems at all so far. But the reason I wanted to update this review is that Oratory1990 just released a new EQ set for these phones. I changed my settings to the new values and spent half an hour or so listening to my typical evaluation tracks to see what it might do. The answer is that the changes are modest but the audible benefit is very positive. Those who object to the brighter highs with the default phones or the older EQ settings should be pleased; the slight "excess" brilliance at the extreme top seems to be less noticeable and more in balance with the tracks I've played. Also, the bass boost and turnover ended up closer to my modified settings, meaning the bass is extremely solid and deep right out of the gate, with no midbass prominence. The mids are still gorgeous and lifelike. If you like these phones at all, and are willing to EQ, try the new Oratory1990 settings and enjoy!
Would recommend to a friend.