Preface

The “low” end of the Hifiman classics that is recognized alongside the lineup of the legendary HE-500 and HE-6. You rarely see these on the used market nowadays since their release about 7 or so years ago (before I started even in the hobby). I’ve read posts from previous owners (and current owners) about the touted bass on these as being fun and enjoyable when compared against the HE-500, and does not reach the bass quality of the veneered HE-6 when powered through speaker taps. This made me really curious about the performance of these when compared against my HE-500 and was fortunate to purchase one recently at a good price.

I’ll skip over some sections given that this is a used, discontinued model; there isn't much to talk about with regards to other tangibles (i.e. packaging, accessories). When I got this, it had a broken original SMC to 3.5mm cable, had the stock velour pads, and the HD650 padding stuck on the headband (similar to my HE-500). With those out of the way, let’s get to the review.




Build and Comfort

Build quality is classic Hifiman; decent looking and heavy. There have been reports of this style of headband failing because the glue holding the headband sliders eventually weakens - I fortunately have yet to experience it on my HE-500, and this doesn’t seem to be the case with the HE-400 I bought used. So count me on the statistic of “still in working condition” Hifiman QC count.

I had the HE-400i that was released in 2016 with the suspension strap and on a personal note - I preferred that headband system because of the weight distribution being better compared to the singular band present in still current models like the HE-4XX and HE-5XX. That aside, the headband is reasonably comfortable overall… for the first couple of hours. After that, I feel a hotspot at the top of my head, which I attribute to poor weight distribution on this particular style of headband. I feel the same with the HE-500 and this weighs slightly less than that.

For the pads, the stock velour is just plainly irritating to my skin. It just passes what I consider to be comfortable. I’ll cover a short section about the sound when used with the stock velour, but I immediately replace it with the Dekoni Elite Velour for Audeze that I have and used for my HE-500 (currently in hibernation while I play around with other cans). How do the Dekonis feel? Predictably, much better and I’ve since then been using these as my pad of choice.


Amplification

These are rated with 92.5 dB sensitivity and 35 ohm impedance. This is neither demanding nor easily driven - about smack in the middle of having enough volume out of a decent source, but likely not enough headroom for highly dynamic tracks at louder than my preferred listening levels. They can run off an iPod just fine without me noticing any loss of quality. Heck, I don’t go past 9 o’clock on the JDS Element dial, and only go around 10 when EQ is applied. You don’t need a high wattage output amp for this based on my experience. Take that as you will as there are others who would slide in their comments about using speaker taps improving the bass and such - I am not one into trying that route so you can discuss with those individuals about them.

On a side note, for people’s reference, I usually listen anywhere between 60 dB - 75 dB.


Sound

As I mentioned in the comfort section, I did not find the stock velour very comfortable and instead chose to go with the Dekoni Elite Velour for Audeze. If you wanted a short summary of how the stock velour sounded to my ears, here’s the TL;DR: treble can be sibilant at times, bass has decent impact but texture feels lacking likely due to seal or decay and tends to bloom over midrange, midrange definition is overall good - however, it has peaks in weird places that makes some background instruments more noticeable at times and the vocals subdued, but at different parts of a song. I can’t explain it any better than that. But my takeaway is that stock velour has a weird V-shaped tonality. On a final note, there are those who claim that there has been a revision of the HE-400 at some point. I will say I cannot give more details on that and the different revisions as I didn’t look into it too much.

Since comfort and seal was an issue for me, I opted to go with the Elite Velours I used to have with the HE-500 - so essentially both my HE-400 and HE-500 are evaluated with the same pads (talk about consistency). The review moving forward consists of the HE-400 with the Dekoni Elite Velour for Audeze pads installed.

Further, I have not been able to find a reliable frequency graph measurement of these, so this will essentially become a completely subjective review without confirmation to my ears of what I hear. Guess this is the most subjective review I’ve written and you can put as much salt as you want with it, but I’m winging it so let’s go with it.

My music testing mostly involves modern tracks, OSTs, classic rock, 70s to 90s pop.


Overall Sound Signature

With the Elite Velours, the HE-400 is warm sounding, similar to the HE-500 but with some distinct differences (which we’ll touch later). The overall balance is decent in my opinion, bass comes across as warm, midrange has good definition, treble has enough energy to not make the tonality dull. I would classify this as warm-neutral with no EQ and is fairly enjoyable for modern tracks.

Bass

• Extension is good, but slightly behind the HE-500, rounding up to around 35Hz or a bit higher
• Bass is quick in attack, but texture is a bit unrefined, like they’re a bit loose. I think some would describe this as lacking “tightness”. This may have something to do with decay being slower compared to others I’ve heard. You can still distinguish the individual bass notes though
• Bass extends a bit to midrange, giving off a warm transition to the lower midrange
• Bass impact/slam is good, but I would have preferred more. Impact is a touch less than the HE-500 from recollection, and lesser than the Focal Clear I had before.

Midrange

• Lower midrange I feel has decent texture and definition. Male vocals have good quality and weight
• With the bass extending its transition to the lower midrange, this seems to add a layer of thickness to instruments like electric guitars, which makes them slightly incorrect sounding
• Upper midrange is a bit weird. Some notes are more prominent than others on certain tracks, which I find odd because other headphones don’t bring out such pieces in a song. Some brass or violin notes will come out with more volume than say the lead vocal at certain parts of a track, which I don’t experience with others like the Clear, DT1990, HE-500 and such. Not sure if this is what others would typically describe as ‘wonky’
• Piano notes have good texture and definition. *Some* female vocals seem to lack weight, while others sound fine
• Vocal transition is good, similar to the HE-500 and DT1990 in quality, but maybe just a touch slower and not as smooth in transition

Treble

• Treble air quality seems hindered a bit, like the 10kHz region is more subdued than preferred, adding to the overall warm tonality
• Presence region (6kHz - 8kHz) has enough energy to give liveliness in a song, but seems to have some lingering effect on the consonant range and some ringing effect of some sort
• This presence region makes some consonant ranges and cymbal crashes sound sharper than what I prefer, but it’s not in the level of annoyance as the Focal Clear or TH-X00
• Overall passable treble balance leaning towards the warm side with a slightly peaky presence region

Detail Retrieval (Resolution) and Dynamics

Overall good, but maybe a step behind against the HE-500 and DT1990 in stock tuning with the Elite Velour. There seems to be some weird peaks and dips in the midrange to upper-midrange section that’s causing some details to share the center stage with other instruments at different times. Once EQ’d, it fixes this unusual detail retrieval presentation to something that sounds more normal. With EQ, I would rate the detail retrieval and resolution only a half step behind the DT1990 and HE-500.

Dynamics is also a positive for me. Bass dynamics and slam are a bit behind the HE-500 IMO. Initial leading attack on the upper midrange to treble region seems somewhat blunted, likely caused by the weird midrange peaks it has. It’s just slightly dampened when compared against the HE-500 and I would attribute the cause to be from the weird upper-midrange to treble balance. Even with the good dynamics, cohesiveness of the different instrumental pieces are great and something that makes music listening engaging. Overall dynamics is still behind the Focal Clear to my ears, as I think Focal is still leading in this technicality.


Head stage and Imaging

Like my other reviews, I don’t give this technical ability too much notice since most of the songs I listen to don’t require me to concentrate on this aspect. I usually multitask when I’m listening, I don’t often listen to music just to listen. I will say that the head stage presentation is about average, stage width = average, imaging = no glaring flaw to speak of. It’s cohesive enough across the 180 degree listening stage for me.


Timbre

Overall, a bit coloured and lacking in naturalness to my ears. There is this weird dips in the upper-midrange that makes female vocals sound a bit odd at times. Further, there is this ‘plastic’ effect that is noticeable when the presence region is reached, namely in the consonant range. I suspect this comes to the decay of the drivers that’s hinting at a somewhat plastic sound after the initial consonant range is pronounced. (What I mean by plastic effect, imagine tapping a ziplock bag and the sound of that plastic crinkle - that’s the sort of sound I hear during the decay of the consonant range pronunciation).

Instruments like piano, acoustic and electric guitar sound tonally correct for the most part. What some of the instruments lack is that initial ‘bite’, which I will attribute to the combination of upper-midrange and treble balance.

In summary, it’s not as natural sounding as the HE-500 in stock form. However, it’s not overly coloured to the point that it sounds completely incorrect. It just adds some colouration that some might find enjoyable. I certainly enjoy this type of colouration on some songs, but not so for others. The thing is, if I don’t find it consistently correct in timbre on the majority of the well recorded tracks I listen to, I can’t give this particular category a good mark. Timbre quality is just on the passing line grade for me.


EQ

As always, EQ for the most part fixes the tonality section and some of the timbre issues. The midrange to treble balance has for the most part been alleviated for me. The ‘plastic’ decay quality in the consonant range has also been reduced significantly, so only a hint of it remains with the EQ profile I use. Bass has also reduced its uncontrolled texture and over-reach to the lower midrange. It’s still not quite as impactful as say a Focal Clear, but it’s more linear sounding which I prefer. This headphone takes a lot of EQ’ing to get to my target curve, but once it reaches my preferred signature, it has been pleasant to listen to.

Among the most interesting things about the HE-400 EQ’d and the HE-500 to my ears, is that it makes voices (especially female vocals) sound like they’re not coming from a set of speakers, nor does it sound like a playback recording. I can’t quite point to it, but there is this certain sense of texture in the vocal range that makes them sound like they’re right there with you, as if they are life-like in quality. Besides these two, the DT1990 EQ’d is similar in quality for this but maybe marginally behind. Of course, your findings may vary as our experiences differ. We tend to differ in what sound texture we look for that registers to our perception of what sounds real or not.

At this point in time, I’m EQ’ing almost any headphone I get nowadays. The only exceptions so far that I find doesn’t need EQ to sound great are the HE-500, HD600 and Focal Clear. For the HE-400, I am one to recommend EQ with them. This is not to say that they are un-listenable in stock form. No. You may like the stock tonality for sure, but to my ears, the stock tuning is not something I would openly recommend to the next headphone enthusiast.


Comparisons

Hifiman HE-500

How does it compare to it’s older brother? They share some characteristics (other than their design and build quality). In stock form, the HE-400 tonality is more V-shaped, while the HE-500 is more linear sounding. The HE-400 hits my sibilance sensitivities for certain tracks, whereas it is absent on the HE-500. The HE-500 has the better extension on both bass and treble to my ears on both ends than the HE-400.

With an EQ’d HE-400 vs HE-500, I can’t say yet. The HE-500 is in hibernation for the time being as I expect my perspective will change and have this particular guilt on why I keep trying out new headphones when this is close to my ideal signature overall. Both are discontinued anyway so it doesn’t matter too much since these come every so often in the used market. Still, I would say the HE-400 EQ’d is a good alternative if you can’t find the HE-500, and I find the HE-400 the more ‘fun’ sounding of the two.


Hifiman HE-400i (2016 2.5mm version)

I haven’t heard the HE-400i in a while, so I’m only going by memory of it’s overall tonality - bright neutral. There is a presence region shout that can become sibilant at times. I like the bass better on the 400, but I didn’t really play around with EQ on the 400i so I can’t say much about its potential other than the stock form bass is quite lean in texture despite being tight and quick typical of all the planars I’ve heard so far. Head stage width is also narrow on the 400i for some reason, it could be my unit is defective or my dac/amp setup at the time (E07k/E9) is causing problems with it.

Comfort also goes to the 400i with that suspension strap structure distributing weight better.


Sennheiser HD600

One of the iconics in the headphone world. As I’ve mentioned in the other sections, if someone is looking for a no-frills headphone that sounds great all around without needing to mess with any other DSP tools, the HD600 is the choice. It has an inoffensive tonality and good technical abilities, hence why it’s been recommended time and time again despite its flaws when compared to certain headphones people prefer that’s not a Sennheiser HD6X0 series.

When an EQ’d HE-400 is put up against the HD600, it becomes more competitive. With the profile I use for my target curve and earpads, the HE-400 I find is better in almost all fronts (except for comfort) by a small margin. It’s a bit more dynamic, a bit more engaging, with vocal qualities that so far is at the top of my list. Feel free to disagree, because that means we already differ in perspective, and I’ve mentioned on my section about Timbre that this (EQ’d) and the HE-500 have vocal qualities that I find special compared to the rest I’ve tried. I'm not with the majority that find the HD600 vocals to be realistic sounding, only tonally correct sounding (if this is what most would mean by 'natural' sounding).


Conclusion

For a discontinued model made around 2012, I feel this is one heck of a bargain at its used market price (<$150). Hifiman’s double-sided planar in the HE-400 and HE-500 have some special quality to them that I find isn’t quite captured in the newer HE-400i released in 2016. I can’t say if the newer Hifimans are able to replicate it, but from most that I’ve read around, it seems the Hifiman sound is a bit different nowadays. Better to ask others who have the OG 400 and the newer ones to compare it to.

I can wholeheartedly recommend the HE-400… if you meet majority of these criteria:

• Have strong neck muscles
• Confident in doing even simple mods on them (i.e. pad change)
• Likes a semblance of V-shaped open back tonality in stock form
• Use EQ to fix flaws in the signature
• Likes a ‘fun’ and ‘engaging’ pair, however you perceive a headphone as being those two adjectives

The stock tonality is just a pass for me, and is something you might want to hear for yourself. Stock velour pads become sibilant for a number of songs I listen to, so that is an off mark for me. Further, stock tonality is not very correct sounding to me. However, at the price they can be had at the used market for less than $150, I’d still put this on my list of ones to obtain.

Overall grade comes down to the following:

• Stock tonality - 7.3 / 10
• EQ’d tonality - 8.5 / 10
• Comfort - 7 / 10
• Technical Abilities - 8.2 / 10

Because of how good I find these when EQ’d, I will be giving them a score of 4 / 5 here. Excellent sonic performance with decent comfort at the market price gets a high mark from me.

Thanks for reading my lengthy write-up.

I have owned my HE-400 for over 3 years now. I have gone through a love hate relationship with them as they simply are not the jack of all trades headphone I was looking for. However, over the years I began to appreciate their outstanding qualities they do posses. These cans go incredibly good with trip hop, hip hop, instrumental and orchestra. Vocal based music is a hit or a miss. Males can end up sounding quite a bit deeper but sometimes missing that organic warmth due to the rise of the 1k region and scooped mids after which make vocals sound nasal. Same applies to women vocals, but that is caused by the peaky highs. Again this depends on the track and how it was mastered. Bright songs tend to be too peaky and the highs on this headphones do not pair well with that, warm mastered songs have no problems. However, movie soundtracks, movies themself, games, instrumentals and complex passages are fantastic. American music sounds fantastic too think of hip hop, rap or pop songs. Their imaging and soundstage are good for gaming too. These headphones have lightning fast transient response, and have a tremendous way of imaging the sound in this almost holographic fashion. They tend to still give me that surprise or waw moment even after all these years. They do sound better when around the 90db mark and not lower, but listen with care people. Also, make sure your room has no fridge or such in the background as any background sound messes with this headphone's clarity. They leak massive amount of sound so it's a headphone for private listening. All in all, these are definite keepers. They are so good for their price range that I decided to buy a second pair in case they become too rare over time. This headphone is a clear step above dynamic headphone offerings under 500$. Their achilles heel is that the stock frequency response is not for all tracks which is also why I will buy a HE-500 alongside these, comparisons will be made in the interest of time. If you are looking at Planar's look at the HE-6, HE-500 or these. The double sided magnet design give them a more organic and speaker like presentation that not even the newer planers from Hifiman can match.

These are amazing, especially when paired with the EF-5 amplifier. Would recommend to people looking at headphones under $500. The quality and soundstage is unbeatable, works wonderfully with all types of music.

Most people hate this headphone because of annoying treble spike and low mid treble but if just need to tweek EQ to see its potential.

I'll start by saying that I have not owned a great deal of various pricey headphones. These are my best cans so far, but I've listened to a couple other comparable headphones that I'll mention later. Also, I'm not aiming to write a comprehensive review - some others already did a much better job at that than I will ever be able to. What I aim to do is point out the only fatal flaw I've found in these headphones that I didn't see anyone else mention, along with some other impressions.
 
My background: I listen to a whole lot different styles of music (from folk to IDM to ambient to jazz to blues to rock to pop to rap, just to give an idea). Over the years I've realized that the best sound is monitor sound. The playback device should introduce as little distortion as possible. The first really good headphones I've heard were my friend's Shure SRH-840. Then I bought myself German Maestro GMP 8.35D - awesome headphones widely regarded as fit for studio work. And then I've gotten HE-400.
My system is a Windows 8 laptop -> EMU 0404 USB -> headphones. Additionally, I own the O2 headphone amp and I have tried taking the sound from EMU's linear output and putting it through the O2 instead of using the EMU's built-in headphone amp. Unsurprisingly, I could hear no difference whatsoever. Because, well, 0404 is a solid device. EMU has less power, but it wouldn't mean I would be less deaf if I listened at peak volume - both amps are perfectly capable of producing over-the-top sound pressure levels with HE-400.
 
Build quality: I have no complaints. One thing I've noticed is a tiny bit of play in the ear pads where they are attached to the driver housings. It's not an issue at all, but something I would reasonably expect $400 phones to be free of.
People complain about the cable connectors, but I've detached and re-attached the cable a couple times and had no problems doing so. The connectors are clearly not convenient, but not in any way problematic. And because they're screwed in you don't have to worry about sudden connection loss.
The painted white logos wear out extremely fast. So would the L/R marks, but those are cleverly placed where you hardly ever touch them so it should be fine.
 
Comfort: I generally don't have problems with headphones at all, but HE-400 are clearly a bit more comfortable than GMP 8.35D thanks to less clamp force. They're heavier, though. I can feel them on my head, but I've never been uncomfortable yet. The only minor complaint (and I have the same problem with many other phones) is the headband cannot be adjusted to be short enough to fit my head well. It's just a tad too long in its most retracted position, so the earpads touch the upper part of my ear due to the headphones sitting too low. I'm an average height and build person with an average head, so not sure what's wrong there. Perhaps, my ears sit higher on the head than usual? Anyway, GMPs and HD580s have the same problem. I need to almost place the headband on my forehead to compensate for the extra length.
 
Sound: I won't specify a list of recordings used as some other reviewers do, simply because I've had the phones for years and listened to a whole lot of music from my collection of 29K tracks.
Just one example would be the album "Roadhouses and Automobile" by Chris Jones which is widely regarded as having great recording quality.
 
At first HE-400 seemed slightly superior in every aspect compared to GMP 8.35D (which, I'll remind you, are very solid phones and that's not just mine opinion). The main difference was slightly wider soundstage, and generally the sound was different in a way I couldn't pinpoint. Then I've listened to Sennheiser HD580 and realized this must be what open headphones sound compared to closed ones. I clearly hear this difference (that I still cannot exactly describe nor do I understand why it even occurs). I cannot claim I hear any specific planar / orthodynamic / isodynamic sound, though - all I hear is decent open headphones.
Bass is just the right amount and very deep. I was afraid these open ortho headphones would not match closed GMPs, but they do!
These phones are slightly more detailed than GMPs as well HD580s, and they seem to have quite flat frequency response across the whole range.
But here's the catch, and I only noticed it recently: I was listening to Rob Halford singing "You've Got Another Thing Coming" on the 2005 Japan remastering of the Screaming For Vengeance album, and I've noticed unpleasantly harsh sound. Then I've found some other tracks that displayed the same problem. Long story short, there's a peak somewhere close to 1KHz. I don't have the equipment to pinpoint it, but adjusting the 1KHz slider of a 20-band digital equalizer by approx. -4 dB solves the problem. I would rather use a parametric equalizer, but again - don't have the equipment to find out the right frequency, Q factor and attenuation.
 
Summary: solid headphones, very versatile, almost monitor sound quality with the right amount of everything except for a narrow frequency response peak at ~1 KHz that will make some tracks sound very harsh and loud (some vocals, harp, trumpet can strike this spot).

Hey guys!

I know this is hardly the first review of these to ever be posted and I'm pretty sure everyone has covered all of the bases by now, but I've decided to throw in my two cents as well.

Introduction:

This is my first review here, so please don't lynch me.

I've owned these for two years and they have a special place in my heart as that one gateway drug that led me, not only to planars, but also to the higher planes of audio... Or so I like to think. Things have changed in the past two years and if you are looking for a good value, open-back planar, this is still a decent choice, but you might want to just pick up the HE-400S, since it has many improvements over the original.

Build Quality:

Ok, so to get this understood right off the bat - the build quality is good. It is. High quality material was used, the headphones themselves are mostly metal, the headband itself is also metal with a leather exterior.

However the design is not great. So to re-iterate, we have high-quality components, which have not been put together in the most ingenious of ways.

While the headphone itself is very sturdy, it has its issues:
 

1. The metal support for the headband si connected to the metallic casing of the driver through a screw on each side of the driver's casing. Now, the problem with these screws is that they have an uncanny tendency to unscrew themselves, so you have to screw them back in, which is quite frustrating. You don't even need to move around too much for it to happen, but it does.

 

1. The cable connectors... Ah, the lovely, lovely Hifiman solution for cable connectors (thank God, they've changed these with the newer models). They're something similar to reverse coax connectors, but I'm not really sure what. Either way, as the metal headband support screws, these also unscrew all the time, which is very, very frustrating and very damaging to the cable, in the long run.
   
   This can easily damage the cable as you need to rotate it to screw it in. Sure, you can rotate it in the other sense to compensate for it, but most of the time you're not going to get roatate in the opposite direction exactly as much as it needs to be screwed in and that will cause tension in the cable, which, in time, will damage it. For example, my Canare 3m cable died after about one year of usage and I had to replace it with the Silver-coated OCC 3m cable from Head-Direct
    
2. Stock pads constrict the sound and are not very comfortable. I'm sure that many of you are quite familiar with the "pads change the sound" phenomenon and it's true. The stock pads seem to take out some of the depth of the sound, it's like there's a very, very thin layer of plastic between your ear and the headphone.
   
   Additionally I spoke about the comfort. I am somewhat biased towards velour pads, because I like them more, due to not having them stick to my ears after long listening session.
    
3. Another issue is the weight that so many planars have. The HE-400 weighs about 440g, that's a little more than Fostex's T20RP MK3, which weights 328g and the Oppo PM-2 which weighs 380g. Additionally, the Newer HE-400S only weighs 350g.
   
    
4. The headband is not self-adjustable. I know a lot of people don't have a problem with that, but I prefer those, because they usually adjust accordingly, so I don't end up moving them by mistake and then not having the proper fit on my head and wondering what's wrong for a while... I imagine not many people run into this problem, though.

 
 
Sound Quality:
 
Ok, now here's the most important of them all. The sound quality.

Setup: I'm currently using my desktop PC, using a Oehlbach XXL DAC Ultra connected via USB (32-bit, 192khz) into which I plug my HE-400 directly. I have also used them with a Creative Sound Blaster Zx and a Asus Xonar Essence STU, but I will just talk about how it sounds with the Oehlbach, because it is the most fresh in my mind.

I'm using Foobar2000 as my player and my files are mostly FLAC or WAV, but I've also thrown in the occasional mp3.

I listen to all types of music, so I decided that I'm going to "audition" them and present their capabilities using multiple genres. Some of the songs I used are:

Michael Jackson - Thriller
Aerosmith - Dude looks like a lady
Queen - Keep yourself alive
Disturbed - Indestructible
Jesse Cook - Mario takes a walk
Queen - Another one Bites the Dust
Nova Menco - Journey
Joe Satriani - Surfing with the Alien
Steve Vai - Earthquake Sky
George Benson - This Masquerade
Guns n' Roses - Nightrain
Diana Krall - Fly me to the moon
Lee Ritenour - Night Rhythms
Ola Gjeilo - Ubi Caritas
Funkadelic - Maggot Brain
Infected Mushroom - Heavyweight
Pink Floyd - Comfortably Numb
Christina Aguilera - Hurt
Frederic Chopin - Grand Valse Brilliante (Interpreted by Valentina Lisitsa)

The tracks which I found more relevant are in bold and I will provide an explanation of why I found them to be important to my listening impressions.

So, right as you start listening to these, you can hear the immense soundstage and detail retrieval, they are really great, especially if you come from a closed-back headphone. Which I did, I tried them right after work, where I use a AKG K66. Not much of a comparison, I know, but it makes the WOW factor all the more obvious.
 
Michael Jackson's Thriller is a big-time hit for me. I've always loved this song, ever since I was little, but hearing it on a pair of HE-400 is completely different than hearing it on... Say, my old NEI television set, on MTV. I love this song and I listen to it when I try out headphones because of the great imaging and spaciousness it provides. From the start, when the synth and bass come in, you can tell that everything has taken its rightful place, being set just where they're supposed to be, offering a beautiful, beautiful imaging. It's not just once I've found myself pausing after the howling of the wolves, wondering what my neighbor's dogs are doing and why they're going nuts... Then I just realize that it's my music.

Aerosmith's Dude looks like a lady I use due to it's intermittent stereo sequence at that start. I generally blast the volume really high and see if there is any noise coming in between the guitar segments, in the quiet passages. While I did hear some noise, I later found out that the matter lies with my Oehlbach, not with my HE-400.
 
Queen's Keep yourself alive is a great song to show off the nice, smooth mids and incredible detail retrieval of this headphone. As soon as the song starts, you hear the guitar. You hear the pick strumming the guitar strings. You hear the edge of the pick grinding against the edges of the thicker strings' exterior metallic wrapping. It's fantastic to hear this much detail and it is quite soothing.

Indestructible, by Disturbed is, by far, my favorite workout sound... But as you can imagine, I don't really go to the gym with my HE-400, I simply enjoy the song at home, sometimes and that truly isn't difficult to achieve, as the HE-400 brings a great bang and slam with its bass, as soon as the instruments kick in. You can feel their "raw power" and their energy right off the bat, but sometimes it gets a bit too harsh (more on that later).

Another one bites the dust, by queen, I find to be a great tool for listening to bass and sub-bass and boy, does this headphone shine here. The bass is nicely balanced and controlled, without being bloated or feeling artificial in any way. It has depth and it packs quite the punch. It's full and it's not the type of fatiguing bass I've seen with some very V-shaped response headphones. I truly enjoyed it, despite being more inclined to a more mid-centric orientation.
 
Earthquake Sky is on this list because you can easily hear the nice slam of the drums, which really puts the lower range of these headphones to value.

Nightrain is just on this list because it's my favorite song of all time and it proves that, even though I love Slash a lot as a guitarist, Izzy Strandlin was quite under-rated and its that specific underdog effect that makes the first solo of Nightrain my favorite guitar solo of all time... Also the highs sounded harsh and edgy. That was unfortunate, this is one of the few times in which the high quality version of the recording was a poorer experience to me than the low quality mp3.

Funkadelic's Maggot Brain is a song I got into when I was in high school, just learning guitar. This is also one of the first lengthy solos I have ever learned, so it's quite special to me. Half of it sounds as smooth as a summer lake at dawn, really showing how the mids are well-balanced within the whole sound, showing off a very detailed sound. As for the other half, the higher-end of it all, it sound abrasive, if felt like sandpaper was being rubbed somewhere close to my ears, at times.
 
Infected Mushroom's Heavyweight is good as it takes you through so many sound, building a complex imagery around you, showing you how well individualized this headphone makes everything, giving proper air between each instrument and having everything settle in just right.
 
Christina Aguilera's Hurt, now that's a song I really enjoy and its depth gives me goosebumps every time. It's about regret, it's about not saying what you were supposed to, what you wanted to, at the right time, it's about missing out on important things in life, like family and the loss of a loved one and also about the difficulty to move on after such a tragedy, it's about... Those damn high peaks that ruin everything. There are seriously some weird high spikes in the upper range of the spectrum which can be heard throughout the song. There is also some slight sibilance and just a general sense of unwanted edginess and this time the fault is not with my Oehlbach, nor was it with my Creative X-fi Xtreme Music, nor with the STU...
 
This, my friends, was the biggest flaw in sound quality I found with the HE-400. It can be partially resolved by equalizing the headphones somewhere between the 9-11k, but nobody really wants to do that. Nobody wants to spend a lot of money for a headphone in order to make it sound right. Of course, I'm not saying it sounds bad, but flaws like this can be quite bothersome, especially when they're so obvious in songs you really enjoy.
 
Additional Notes:

They're easier to drive than most planars, but I wouldn't recommend using them on your phone.
They're not portable and are not meant to be, they don't fold, they're not closed-back, they don't have a carrying case/pouch.
The HE-400 can be used as a small, mono speaker if you have a powerful enough amp.
Hifiman HE-400 are moddable, they can be modded in many different ways in order to tweak either sound or comfort. I have not tried any of these mods, all I have done is change the pads on mine and I'm happy with the result.
They come in a cardboard box, with a plastic support, but I don't care since I don't want to pay a premium for the packaging anyway.
 
Conclusion:
 
These are a beautiful way to into things, whether it is high fidelity audio, planar magnetic headphones or just another plane within the Nirvana of good music. Sure, they're a bit clunky, a bit uncomfortable, but they provide great value for the money. The sound quality is great, but it could be a bit better. They'll always provide a good experience, but most of the time they'll provide a great one.
 
Within the context they were released in, all those years ago, I would give them four stars, but now with the existence of the much better, many-times-over improved 400S, I give them  three stars. Mounting that up to an average of three and a half stars, which I think is fair.

Apologies if I forgot to mention anything (I'm writing this while at work, don't tell my boss!), I will update if I find it necessary and may return to post some pictures of the headphones.

Thanks for reading, let me know if you have any question (though I doubt it, at this point).
 

These are warm but detailed. They are fun to listen to, like the other Hifiman products (I have a couple).
 
I enjoyed using them and got a HE560.
 
Will give them as a gift to somebody. They are nice open headphones for the price. I can expect they will enjoy them.
 
Still working after a year of use.

sorry my English is Google translate

The sound of these hifiman immediately like it or hate it.
They have a strong character, perfect bass, brilliant highs, medium tone mind incorrect.
A few years ago I was involved with live recordings of classical music and I used the stax lamda pro (magic but delicate) and Sennheiser HD 600 (less magical but tonally correct) as monitor of post production.
After so many years I decided to try this hifiman hoping it was a mix between strax and Sennheiser.
Ok I was wrong, hifiman has a different sound.
For two weeks I sailed between Acdc, metal, in exaggerated volumes.
Then I got the Audio Gd NFB 28 and headphones were taken off, especially in balanced.
Too bad the rest of the music I was interested less than usual, then I realized that the particular signature sound port to listen at high volume that kind of music.
Loreena McKennitt's not good! His voice changes tone is darker, the musical instruments that are riding the midrange suffer.



Il suono di queste hifiman piace subito o lo si odia.
Hanno un carattere forte, bassi perfetti, alti brillanti, medi timbrica mente scorretti.
Qualche anno fa mi occupavo di registrazioni live di musica classica e usavo delle stax lamda pro ( magiche ma delicate) e sennheiser hd 600 ( meno magiche ma timbricamente corrette ) come monitor di post produzione.
Dopo tanti anni ho deciso di provare questa hifiman sperando fosse un mix tra le strax e le Sennheiser.
Ok ho sbagliato, hifiman ha un suono diverso.
Per due settimane ho navigato tra Acdc, metallica, a volumi esagerati.
Poi mi è arrivato l'Audio Gd Nfb 28 e le cuffie hanno preso il volo, soprattutto in bilanciato.
Peccato che il resto della musica mi interessasse meno del solito, poi ho capito che la particolare firma sonora porta ad ascoltare a volumi alti quel genere di musica.
Loreena McKennit Non va bene! La sua voce cambia tono, è più cupa, gli strumenti musicali che sono a cavallo della gamma media soffrono.

The price to performance ratio of the HiFiMan HE-400 is truly exceptional. The clamping force of new head band is tight and requires break-in. I prefer the the plush pads over stock pads for comfort. Once HE-400 is broke in, like a pair of old boots...they become comfortable but not super comfy..due to the weight of these cans being on the heavier side. 
 
Equipment used for this review
 
HiFiMan HE-400
 
HiFiman HE-300
 
Grado GS1000e
 
Bose ae2
 
Decware Zen Head amp
 
Emmeline "The Black Bird" SR-71A amp
 
Schiit Valhalla 2 amp 
 
Modifies Play Station1 CD player
 
iPod classic 160gb
 
iPhone 4s
 
ALO Audio 30pin line out dock cable
 
AudioQuest cables
 
All tunes sourced at CD quality bitrate 1,411 kbps, iTunes, Tidal music player, CD's, WAV files
 
 
 
 
 

 

This is one of my few reviews, Im not a type of person to give reviews when buying an item but this time I had too. I was looking for a good setting to have a portable hifi system and I knew to achieve this its not coming for cheap but also I had a budget. After reading many reviews I decided to go for these planar headphones the Hifiman He-400 and also bought the Fiio X3 to drive them with.I was so excited when I received them that I couldn't wait to try them on. But to tell you the truth I wasn't that satisfied! Yes its true you will hear instuments and clearness that with my other equipments I couldn't but I love to listen music load and perhaps without losing from quality thats why I spend around 400 Euros for them but with Fiio X3 at full power wasn't so impressed. I thought that these headphones were not driven hard enough so I decided to go for an Amp. My choice was between C & C BH  -  Fiio E12   - Cayin C5. But finally I choose the Cayin C5 and theres were the magic begins. BANG it was amazing. This great Amp was helping the Fiio X3 driving these beefy Hifiman. With the boost turned on from my amp I could still enjoy a crystal clear quality and I couldn't believe the sound was coming out from this equipment and getting the best from these headphones. Finally I spend around 500 Euros but now I can say they were well spent

Engineer's dream, but lacks any comfort.  3 month owner.  
 
Pros:
Sound Quality excellent -
      Lows - shame on you if you don't already know these are bassy.
      Mids - average sound quality.  limited range, but great detail.
      High - slightly 'punchy'/undetailed and a bit bright, but still great.
No sibilance - you get the point.
Aesthetics - easy on the eyes, great look.
 
Cons:
Weight - padding on headband wears out in a month.  It will hurt your head if you don't bend the medal headband to size accordingly.  It got to the point where I had to make a custom pad for the top of my head.
Ear cushions - synthetic leather can get quite hot.  I tend to sweat with any form of leather, so aftermarket ear cushions were a must.
Cable connection - this is the biggest design flaw of the headphone.  I had my 400's RMA's because the connection point between the headphone and cable broke off.  The actual cable sticks out of the bottom of the ear piece and rubs against your shoulders which is annoying for some.
 
Bottom Line: I researched for dozens of hours on different headphones and consistently heard these were the best in their class. Basically, if you are thinking about buying for sound and would be willing to sacrifice comfort then welcome to your new headphones.  If you have the money then I would recommend buying the 560's as after testing had much better mids.

Setup 1: Win7 PC -> USB -> Modi -> PYST -> Magni
Setup 2: Win7 PC -> USB -> E10k
 
Summary
 
Disclaimer: this is my first review on Head-Fi and I fully declare that I know (nearly) nothing.  Please be kind.
 
Based on the reviews I read here and elsewhere, I chose to go with the HE400's for my quiet, at-home setup.  My primary listening material is electronic house, jazz, and swing, so I figured I'd go with a headphone that everyone described as "fun" and "interesting".  But as soon as I plugged them in I knew something was wrong.  The detail was phenomenal, the bass lovely and linear (and gets notably better with burn-in), and treble surprisingly clear.  But most men's voices, the low notes in women's voices, some cymbals, violas, and french horns all sounded like they were behind a velvet curtain.  On some recordings these headphones are truly spectacular, but almost half the time I found myself recoiling at the bizarre frequency response hole with which I was presented.  After some 20 hours of testing and listening I have decided that $300 headphones shouldn't make me go "ew", and have decided to return them and try some much-flatter HD-600's instead.
 
Physical Attributes
 
The packaging is simple but effective and got the 'phones to me without any kind of damage.
 
Instead of a rigid carrying case, like what I got with my Senny HD 380 Pro's, HiFiMan provides a simple velvet bag.  While this might be good for some gentle kinds of transport, there's no way I'd put these in my backpack or anything.
 
Although bright blue in some photos, in real-life mine had a nice, dark blue colour.  The cans themselves look quite nice, but the headband and its attachments are bargain-basement.
 
Comfort
 
Out of the box the HE400’s definitely have death grip.  Fortunately, the headband is somewhat bendable, so it’s quite easy to reshape it to lower clamp force.  For that matter, if you had some kind of head deformity you could probably bend it to work around that, too!
 
The ear cups are nice and deep and didn’t touch my sticky-outy ears at all.  My HE400’s came with both the pleather and velour pads, and I found that the velours were about 7mm thicker than the pleathers.  The cups themselves are very large.  While this might be good for some people, they were so big on my face that they touched my jawbone and forced my mouth open slightly!  When I think of listening fatigue I don’t often think of a sore jaw, but there you go.
 
While I didn’t find the cable to be hard to manage, one strange consequence of its rigidity was that it pulled my head down.  I found that the cable had such a hard time bending around things (like the arm of my listening chair) that it would pull my head towards where the cable was coiled, on the floor in my case.
 
Despite my whinging, the comfort isn’t that bad, say 7/10, but they’re not a forge-that-you-even-have-them-on headphone like my HD 380’s.  
 
Amplification
 
While it could be that there ‘phones weren’t burned in at all, I did find that my E10k DAC/Amp didn’t bring out the bass in the HE400.  Once I got them home and plugged them in to my Magni I noticed that bass had much more presence, without ever being boomy or overpowering.  Bass is noticeably absent without amplification, though, so don’t listen to the marketing and think that you’ll be fine driving these with an iPod.
 
Sound
 
The HE400’s do most things very well.  I put on Sting’s The Last Ship and couldn’t believe how good it sounded.  Sting sounded perfectly positioned in the sound stage, and the acoustical accompaniments were clear and detailed.  I sat there and listened to the whole album and thought I had found acoustic bliss.  Despite what most say, I found that a lot of classical music, especially Vivaldi, sounded great on these headphones, too.
 
But when I put on nearly anything else I thought of velvet, and too much of it.  The female vocalist from The Moleskins, for example, sounded like she was singing from 5 metres behind her band.  A viola, cello, or french horn soloist sound like they’re playing in a velvet-lined box, and some cymbals sound as though they’re not even on the same sound stage!
 
So what is causing this?  The 2,000 to 6,000 Hz frequency response hole.  If you bring up the FR for the HE400 on HeadRoom you’ll see it quite clearly.  In retrospect I should have known better, but I was expecting it to manifest differently.  Material that is recorded flat presents the hole quite clearly.  It’s only material that is recorded with those frequencies over-amped that sounds truly great to me on these headphones.  And that’s what was going on with the Sting and Vivaldi recordings that I liked.  On my Shure E2 IEMs (my favourite reference monitors to date) Sting sounds way too forward and Vivaldi harsh.  The FR hole in the HE400’s was simply flattening those out for me.  Unfortunately for the HE400’s, most recordings are between flat and laid-back, and the more laid-back the worse the recording sounds on them.
 
Conclusion
 
The HE400’s are great headphones for some recordings.  They have a velvety-smooth signature, great detail, and amazing channel separation.  But when I add up the frequency response hole and the comfort issues I experienced I have decided to return these headphones and try something else.
 
Would I buy these again?  Probably not.  If I were to go for some more orthodynamics I’d go with something with flatter tuning.  Still, this was a fun experiment and I get to exercise Amazon’s return policy, something I don’t do often.
 
Arriving next week: Sennheiser HD600’s.  At least on a graph, they seem much more attuned to my tastes.

 
As of September 2014, the HE-400 has been discontinued, and it's successor, the HE-400i is being sold in its place. So why publish, or even read, a review now? First, there are many used HE-400s in the market and are being considered for purchase. Second, many retailers still have new stock of the now heavily discounted HE-400, and these are the latest versions with no risk of future revisions. Third, based on 3 days of listening to the HE-400i, I've concluded that the new 'i' version is not an upgrade to the HE-400. It's a different sound signature. Asides from the considerable cost savings, I can see how someone could prefer the sound of the original HE-400 over the HE-400i.

Review set-up;
Source: PC  -> Teac UD-H01 USB DAC -> -or- FiiO X5->
-> Objective 2 Amplifier -> Hifiman HE-400 (Pleather Pads)

Hifiman HE-400

The Hifiman HE-400 is an open-back, over-the-ear headphone with an orthodynamic / planar magnetic driver. It's a break-through in the sense, in that Hifiman achieved it's relatively affordable pricing through advances made in automating the production of the traditionally handmade planar magnetic drivers. Most recent models with this type and size of driver are sold closer to the $900-1000 mark or higher when introduced (the prices come down of course). The HE-400s MSRP is $400, and (as of Sept. 2014) the fact that it's successor, the HE-400i (MSRP: $500) has hit the market, has a street price of significantly way below that.

With a rated sensitivity of 92.5 dB/mW at 35 Ohm impedance, it falls into the  category of high-efficiency planars - headphones with planar magnetic drivers that don't need a powerful desktop amplifier to sound their best. In comparison, the HE-500 and HE-6 models up the line have sensitivity ratings of 89 dB/mW and 83.5 dB/mW respectively. Since dB is a logarithmic unit, an 83.5 or 89 dB/mW sensitivity rating means a headphone will need a lot more power than one rated at 92.5 dB/mW to reach a given loudness level, despite what the  small difference in number would suggest. To reach the volume of a typical live concert (115 dB SPL),  the HE-400 will need ~177.93 milliwatts while the HE-500 and HE-6 will need ~398.34 and ~1413.29 milliwatts respectively. Big difference.

(Note: these numbers are approximate as there is some disparity between manufacturer spec sheet numbers and actual measurements.)

Because of this, high-efficiency planars are in a practically different league from their desktop bound siblings, as they can be used  in a portable rig.  Ideally,  a powerful portable rig, as it still needs a fair amount of power to reach really loud levels. While the popular FiiO X3 and X5 players using their internal amplifiers (which are quite powerful relative to other portable players) can drive the HE-400 to fairly loud levels on their respective high gain settings, it still doesn't sound as dynamic, most noticeably in terms of bass extension and impact, as when being driven by a separate portable amplifier. Think along the lines of the better portable amplifiers, such as the Objective 2 or FiiO E12. The sound impressions written here are based on the HE-400 being amplified by the Objective 2.

Sound Impressions

Have a look at the =3651&graphID[]=3241&graphID[]=353&scale=30]HE-400's frequency response curve, against the curves of the Hifiman HE-500 and Grado SR80i. Notice that there is a dip at the 2000-6000 hz frequencies, but then goes back up at around 7000 hz to a peak at 9000 hz. This is what gives the HE-400 it's somewhat unique sound signature. Vocals, guitar, piano - anything that falls between the 2000-6000 hz range is attenuated or sounds further away, with the details being masked by the other more prominent frequencies, while the peak at the 8-9 Khz range imparts some brightness to the resulting sound. Translated visually, its sound is like a dark rolling cloud with rich tonal variations from black to middle shades of grey, punctuated with bright (but not blinding) streaks of lightning which can actually be very satisfying, depending on the type of music being listened to.

Hifiman themselves have stated that it is tuned for a more 'American' (I take it this means emphasized bass) sound signature, as opposed to the more polite and neutral 'British' sound of the HE-500 next up in the line. The HE-400's bass does have a satisfying amount of slam while still retaining texture and clarity - its massive planar magnetic drivers characteristically being able to render and stop the sound very precisely (transient response). This, combined with the 8-9 Khz treble peak, gives the HE-400 sound signature a satisfying sense of dynamic contrast with a combination of hard-hitting bass on the low-end and some treble 'air' on the high-end, albeit with (or in a sense, because of) a recessed upper mid-range and lower treble.

If you like live recordings of rock bands like Soundgarden, Guns N' Roses or Evanescence, with the thunderous and deep rumbling combinations of drums and guitar bass, and like to listen loud but without any shrillness in the treble from shrieking/shouty vocals, snare drums, cymbals, or lead guitars, you will appreciate the HE-400. In comparison, the Grado SR80i, which is also considered great for rock music, would start sounding harsh or piercing due to emphasized treble frequencies, and have  less bass impact at the same loudness level. Between them, it comes down to a choice between the HE-400's bass slam with good transient response vs. the SR80i's mid-range presence and detailed treble emphasis.

On the other hand, when listening to some acoustic or 'unplugged' recordings which have so much vocal or instrumental richness and subtlety in the 2000-6000 Khz range,  I would prefer either the STAX SR-207 or, to a lesser degree, the Grado SR80i, which will bring those elements forward. While the HE-400 by no means sounds bad with this type of music (it's still better than most 'default' headphones), I would prefer a more intimate vocal presentation - it's a subtle difference that can nonetheless change the way a song is appreciated.

I emphasized the word 'some' earlier because it really depends on how the music was mastered. I have high-resolution 24-bit/96Khz recordings of acoustic jazz with female vocals purchased from E-Onkyo Music, which sound impressively life-like with this headphone. Granted, these are audiophile recordings meant for playback in more technically capable systems, and it goes to show that the way the music is recorded and mastered plays just as significant a role as its genre. For typical recordings of electronic dance music and live rock (not acoustic) sets, the HE-400 generally works well.

 

Conclusion

Sometimes it pays to be late in the game.  Due to a combination of technological developments and price drops due to newer models being introduced, the Hifiman HE-400  scores very high in the price/performance scale. This assumes that the HE-400’s sound signature works with the listener’s music and preferences.  The newer model HE-400i has a completely different sound signature that does not build on the original’s strengths, so calling it a direct upgrade would be somewhat misleading.  I would consider the HE-400i as more of a sidegrade – a different headphone with a sound signature that appeals  for different reasons.

While the older HE-400s sound signature may not be ideal for all musical genres or recordings, when the stars of sound signature, music , and listener preference  line-up, it’s brilliant.  Combined with the Objective 2, it is still very much worth considering for high-end sound, in a  transportable package

Before I own this HiFiMAN HE-400, I owned a pair of Alessandro MS2i Headphones (Dynamic driver, Open) and I thought this was the best headphones. I was wrong until I try this HiFiMAN HE-400 (Orthodynamic aka Planar Magnetic Headphone, Full size). This is an amazing headphones with panorama soundstage, amazing mids, excellent bass, crisp at high, lovely treble is there and this headphones is so comfy. Some people commented it is heavy, quite true, when I first wore it and I felt the weight but after I wear it for couple of times....It just so comfy and comfy is the word that appears in my mind. I listened to this headphones before I went to sleep and it is dark in my bedroom and I closed my eyes.....the panorama soundstage is so big for live music....it just so wide and lovely. I don't really have many negative review for this pair of headphones. I simply just can't find it now. After 50 hrs of break-in I started to get goosebumps and the instructions recommend 150 hours of break-in. I can't wait to reach that hours and see what I feel at that time. If you love musical instrument music, this is definitely the one I will recommend to you. Whenever I bought a new pair of headphones or earphones, I always tested them with my Audiophile Reference IV album. The things that annoyed me is the cable is too long...10ft, it just too long for me. The headband is just too thin. I am looking for addition headband to wrap around it.

After using IEMs almost exclusively, I decided that it was about time to step into the realm of full-sized cans. I wasn't about to spend $1000, but I still wanted better than mid-fi sound. My options were pretty limited, and it came down to either the HD600 or the HE-400. In the end I decided that, despite the HD600's more refined sound, that the HE-400 had what I was looking for (tight, linear bass, excellent detail, and a 3D image). So I pulled the plug on the HE-400 (and a pair of velour pads), and never looked back. 

My first impression was a good one, and they sounded exactly as I expected them to based on measurements and first-hand accounts.

Bass

I'm not at all a bass-head. I find bass to be the must unimportant and non-essential part of the frequency spectrum because it provides little musical information and serves little purpose other than adding body to the music. That said, the quality of the bass is very important to me. I cannot stand liquid, texture-less bass, and I'm not a fan of elevated mid-bass either. Thankfully, the bass on the HE-400 is as far from that as possible. The response is almost perfectly linear, it's extraordinarily tight, articulate, and well-textured. It hits hard, goes low, and does everything that bass is supposed to do without ever getting in the way or disappearing. It's as close to perfect as I can imagine a headphone being in that regard.

Mids

Mids are very important to me. Nothing will ever sound right if there's trouble in the mids, and they're absolutely essential to the reproduction of the human voice. The mid-range presentation on the HE-400 is interesting. The lower mids are very full and somewhat forward, whereas the upper mids are more recessed. They're certainly colored, but it's not a coloration I'd call "offensive." The mids here are very rich and organic without ever sounding thick or syrupy. I think that's partially due to the elevated treble and excellent extension that gives vocals great air and a "breathy" sound. On some recordings the mids can sound a bit distant, but that's not an issue that I've run into very often.

Treble

The treble is the trouble spot with these cans. The treble isn't poor by any means, but it is significantly elevated in the highest octave (10kHz+). The treble can be very hot on some recordings. Some people may like the extra air that comes with this kind of treble presentation, but it's a bit much for me. I find that it obscures detail a bit, and can dominate the signature at times. However, the treble responds very well to EQ and sounds excellent with just a few dB decrease. Extension is great and the the headphones definitely do not want for air. 

Soundstage/Imaging

I've never heard a headphone at this price that presents the audio image anywhere near as well as the HE-400s do. The soundstage is open with great height and depth with excellent layering, and width that is neither unrealistically large, nor cramped. Imaging is excellent, making it easy to pin-point audio cues and effectively sorting the various layers of the soundstage. 

Signature

The HE-400 signature is interesting. It doesn't really emphasize any region, but it somehow manages to be both dark and bright. It's not prefectly neutral, but it's not highly colored. It's just neutral enough and just "fun" enough to appeal to a wide range of tastes. It also responds very well to EQ (particularly in the bass, likely due to the very low distortion and linearity), though I'd avoid messing with the mids too much, as there is a bit of distortion there that can be exacerbated with EQ. However, you can tame the treble and crank up the bass as much as you want with little to no ill effect.

Design/Comfort

I've never had any comfort issues with them, and though the design seems a bit "cheap," I've not had any issues there either. They are a bit heavy, though, so keep that in mind. The stock cable isn't the greatest; it's thick, heavy, and a bit stiff. Don't be too rough with it, because there are reports of it shorting, or the sheath splitting. 

Overall

I've not heard a better headphone in the $300-$400 range (including the HD600). It does just about everything right, and very little wrong (and what little it does wrong is easily fixed). For the HD600 owners out there, they make a perfect compliment to the HE-400. I've not come across a better value in the entire world of audio. 

This is my second mid to high end headphone. And it so far has really wowed me. Im just gonna start with the bass, its amazing. Its very deep and detailed with good impact and texture and its fast, im a bit of a basshead and these will bring the thunder without interfering with anything else. They dig just as deep as my dt770s with almost as much impact and they dont muddle up the mids. The highs have tonnes of detail and are sparkly, but i dont find them fatiguing at all. Mids sound very good on them as well, i really enjoy female vocals on them. Most of the music i listen to is electronic where bass and speed really matter, im running them through my schiit modi and magni, this is a very good combo. The magni gives these lots of juice which planars love. A lot of people say that the leather earpads need to be replaced with the velours. So when i purchased them i got the velours as well, and i found that the velours made the highs way to splashy and the bass slightly anemic. I also find the leathers are quite comfortable after being worn a while. Ive worn them for over 6 hours and havent had any discomfort. They are a bit heavy but i got used to it. Overall this is a wonderful headphone, and its bass can satisfy a basshead without a problem

Full video review below
 

The HE400 from Hifiman is a great value. For someone looking to a.) try a planar magnetic headphone or b.) find a pair of cans that will offer excellent, natural sound at a solid price, then this is one you need to consider. 
 
They're built like tanks! Although the amount of visible plastic is scary at first, its very obvious once you pick them up that they're going to take a few knocks before you have to worry. From the headband (very comfortable) to the metal gimbals to the shielded cable to the plush earpads, the HE400 won't make you feel timid in handling them. Also, since it comes up all the time, I've had no problems with the cable connectors. I can't say why or why not, but they don't seem problematic to me. 
 
It also bears mentioning that the housings are very large. Like huge. Largest I've seen. But they don't touch the ear at all, obviously an intentional design to create a room for the ear (or because of the massive planar magnets required). 
 
Now for the sound.
 
First word that comes to mind: natural. Nothing sounds "enhanced" to these ears.
 
Bass
The bass is solid and reaches quite low without making me feel like I've got a subwoofer on my head. One of the best ratios of quality to quantity I've heard.
Mids
The mids are very clear and neither forward nor recessed. Upper mids are a touch more present than their lower counterparts, but neither sounds unnatural. I can hear all vocals, guitars, and midrange instruments very clearly. 
Treble
The treble is nicely extended but never fatiguing or harsh. I've read a few reviews claiming the 400s were too bright and I'm very glad to say that I disagree. I could see that they wouldn't play too nice with low quality source material, but as they are, the treble is once again, very natural and clear.
 
Soundstage
The depth of stage definitely bests the width although both are still very good. I assume that the room in which my ears are sitting is a direct contributor to this. Once again a very natural sound, no depth so great that I'm left feeling that I'm 30 rows back, but also not so forward that I feel like I'm squished between the bass and drums.
 
Separation
The separation is good, not great. My Grados best it, but that's not to say that its non-existent. Its just not studio recording quality.
 
All in all, I'm glad I've gotten my hands on a pair of HE400s. Although they're a little on the heavy side, they are still rather comfortable and have a great sound. Very organic and natural. They certainly sound best after amplification, but they don't beg for it. Just remember if you're looking at planars, some meaty amplification is gonna get the best out of them for you. 

There really arent much to say.
Everything is good with these headphones except the treble spike.

First off my gear is HeadRoom Micro DAC and Amp.(I don't see how people get by without the crossfeed circuit on older rock recordings) Out of the rather cheap box the high-end was brittle and harsh and the bass boomed. The midrange was just OK. I have a Ayre Acoustics system burn-in disc and after 100 hours of brown, pink, and white noise along with Zappa's G-Spot Tornado from The Yellow Shark these headphones transformed into something wonderful. The highs were tight and accurate, the bass had a lot of power, but was also accurate, and midrange vocals were something to behold. I've always been a Sennheiser/AKG man and had never listened to planars before. For $299 (plus $10 for the velour pads) I don't know if their sound is for everyone, but do yourself a favor and audition these headphones before you make your final decision. I don't think these headphones are going to be powered by iPods or most MP3 players. They are not that efficient and I don't know where the iPod friendly deal started, but if HiFiMAN did they are going to disappoint a lot of people. These are NOT appropriate for mobile use. They leak sound back in the room more than most open backed 'phones do and a dedicated headphone amp with decent gain is required to drive them. I wonder how well the Audioquest Dragonfly would drive them. I'll bet not too well. They may be efficient for planars, but they're still planars. My last pair was AKG K702s and the AKG's were quite a bit louder. I'm curious how the HE-400i's will compare. For 500 bucks they better be an improvement. I spent $150(ProCable Panorama) as I found the stock cable lacking. I know that's a lot of money for $299 headphones, but it was worth it. Plus this cable is well built and should,last for years so when I upgrade I already got the right cable. If I get an amp with 1/4in. jacks, I'll have to send it back to cablePro for a new plug.
 
I know there are better sounding amps out there than the HeadRoom Micro, but none that have a crossfeed circuit. Maybe HeadRoom will start building amps again someday. I just sent it in to replace all the 3.5mm jacks. Getting it back today! Been using the headphone jack on a pair of powered computer speakers with the volume 3/4 of the way up and with the bars on the graphic eq on Foobar maxed out to get more gain. There's just no way any player is gonna be hot enough for these..