HiFiMAN HE-400i

About myself

I'm 38, so my hearing is possibly not the same as in my 20s. I like various music genres, mainly prog rock/metal, blues and some classical music. I'm not into rap/hiphop/EDM so I don't have a strong preference regarding excessive bass quantity.

Some background

I've purchased this item myself, it was brand new. I have no affiliation with the manufacturer nor was this a sponsored review of part of a loan tour.

Unboxing

The headphones are packaged well, the included cable is of good quality.



Comfort and fit

Clamping force is average, the earcup size is big enough. I have average sized ears, but I think this will fit basically everybody. The weight is very light for a planar, no issues with long term listening.



Sound

Simply wow! This was my first open-back headphones which I have actually owned (have tried some before) and the soundstage and imaging was exceptional. Much better than closed back headphones.

Bass has good impact, it is not boomy but has enough quantity and it is detailed.

Mids are clear, and very enjoyable.

Treble is extended, sounds airy but not sibilant. Zero listening fatigue.



Comparisons

With regards to open back headphones, I prefer the HE400i to the Beyerdynamic DT990, which has an overemphasized treble and sounds less natural to me.

I remember that after listening to my ItsFit Fusion a lot, I tried the DT990 and thought "this is not much worse". When I tried the HE400i after the Fusion, my impression was "wow". That is quite a difference



Sources

This is not very difficult to drive, but benefits a lot from a good amp. Less powerful USB dongles may not be enough, but this shines with my E1DA 9038D.

Conclusion

Excellent entry to the world of audiophile headphones. Very affordable, yet has outstanding sound. I think there is a new revised 2020 model that is about $170, which is unbeatable. I can't wait to try more HiFiMAN products.

Review by Mhark Jhoshua Q. Torres

The Company

HIFIMAN has been one if not the best headphone maker out there, they specialized in producing headphones with unconventional drivers, they used Planar Magnetic drivers as the owner, Dr. Fang actually has researches regarding the technology behind Planar Magnetic drivers. Up until now they are very popular in the audiophile realm with several awards and positive feedback. HIFIMAN ANANDA and SUNDARA are few of their new lineups and it is quite popular in audiophile groups. HIFIMAN continues to be one of the top brands in headphone class and it is my personal favorite.

“Easy-to-drive Full-size Planar Magnetic Headphone” this is the claim of HIFIMAN with regards of the HE400i, it is the newer version of the HE400 which is also a hit and was one of the first planar magnetic headphone that is designed efficiently. In my experience the HE400i can be driven by phones to audible volume at max, but it sounds thin and lacks resolution.

Fit, Comfort and Build Quality


The HIFIMAN HE400i, despite being outdated still looks good, the construction of the grills is nice as you can see the drivers when there is enough light to reveal it. The build quality is a mix of plastic and metal, in my honest opinion it feels flimsy and the left and right cups aren’t aligned and it looks off when resting at headphone hanger/stand. I got my 400i as a 2nd hand unit so there are some marks of usage but overall it is definitely presentable. I don’t like the ear pads especially when I compare it with the SUNDARA, it feels itchy and warm to the skin surrounding my ears so the area under the pads becomes more sweaty.

The weight of the 400i is generally light and it doesn’t cause much pain on my neck, it feels comfortable for long hours of listening given the listening area is well ventilated and is at least 3 or 5 degree Celcius below the standard room temperature, because as I said, the coating of the pads feels warm/hot. The cable included is a sleeved type cable, it doesn’t feel premium at all, it gets tangled easily and I find it worse than the cable of SUNDARA. Overall, the build of HE400i is just mediocre, it doesn’t feel premium and the alignment of the cups aren’t great, luckily it feels light and the clamping of the headphone is pretty good too, neither tight nor loose.

Technical Specification:
1. Frequency Response: : 20Hz-35KHz
2. Sensitivity : 93dB
3. Impedance : 35 Ohms
4. Weight : 370g
5. Cable Length : 1.5m
6. Plug : 3.5mm/6.35mm

Packaging


The box of the HE400i looks premium and sophisticated, it beats the packaging of SUNDARA by a notch or two, the box is very solid and is made out of premium materials. Inside the box are the sleeved 3.5mm cable, 3.5 to 6.35 adapter, paperwork and the headphone itself. The package is just okay, I just hope that there’s a carrying cloth bag at the very least just in case you don’t have any headphone hard case and you want to carry it around from home and your workplace. The included cable is just average too I hate it because it gets tangled every time they have contact, I like it because it feels robust and sturdy enough.

Sound

I love gears with midcentric to flat sound signature as I really love listening to vocals rather than instruments. My genre ranges from heavy rock, alternative rock, pop rock, acoustic, pop, jazz and folk. Majority of my test tracks are in 16 bit – 44 khz and 24 bit – 48 khz FLAC file and here is the list of my commom test tracks.

1. Reese Lansangan – For the Fickle (background, female vocals and upper mids)
2. Foo Fighters – Bridge Burning (Imaging, Layering, Coherence, Sub bass and Mid bass, Mids, Treble)
3. Jensen and the Flips – Come Closer (Mid Bass, Mids)
4. Ed Sheeran – Dive (Mid bass, Lower Mids)
5. Norah Jones – Don’t Know Why (Upper Mids and Instruments)
6. Paramore – Hard Times (Imaging, Layering, Coherence, Sub bass and Mid bass, Mids, Treble)
7. Utada Hikaru ft. Skrillex – Face My Fears (Imaging Layering, Bass, Mids, Treble, Coherence, Quickness)
8. Passenger – Coins in a Fountain (Mid bass, Layering, Imaging, Instruments, Lower mids, Treble)
9. Tori Kelly – Hollow (Background, Upper mids)
10. Ariana Grande – Raindrops (Background, Upper mids)

Summary

For the Quality, higher is better as this includes resolution and dynamics while the quantity and positioning are subjective, it actually tells how close and how much the frequencies are.

Bass

Starting with the sub bass, it is well extended and has very good texture, planars are known for their bass and the 400i is not an exemption. The rumbles and riffs are deep and is resolving without being too forward, quantity despite of being a planar is not excessive at all, the sub bass are produced with enough body, great details, and in quick and agile manner. Mid bass, just like the sub bass is being rendered in quick, tight and accurate manner. Both attack and decay are just flawlessly rendered with enough body and weight. Just like the sub bass, the mid bass is placed linearly to slightly forward (maybe due to my warm source and op-amp that I equipped with my amplifier), the quantity might not be enough for bass-heads but the quality is definitely top notch. Despite the known lush sound of planars, the bass of the 400i is rendered in detailed manner, every bass notes are greatly textured and accurate.

Midrange


Lower midrange really depends on the source used and if the right power is supplied, this is the most noticeable part when plugged unamped and amped, it sounds thin and dry when unamped whilst it sounds lush and has good body when amped. It’s hard to find a good synergy too, pairing it with Shanling M3s + JDS labs O2 amp + Burson V6 vivid the details is literally smashing into my face but in return it sounds dry and thin for my liking, on the other hand when pairing it with Shanling M3s + Jazz R7.0 + Thai op-amp, it sounds lusher, smoother, and fuller without losing much details. The positioning of lower midrange is almost the same as the bass, it is just a bit forward, the timbre is natural (amped) and it sounds as natural as it can be. Upper midrange has moderate body, just enough for the female vocals not to sound shrill, it is transparent resulting to calming vocals and string instruments. As far as my journey goes, the midrange and timbre of the HE400i is definitely one of the best, it sounds natural and sweet while the fullness is just enough for it to stay away from being veiled or muddy. Positioning still the same with the lower midrange while the resolution is still great.

Treble

I made the review mainly using the Shanling M3s+Jazz R7.0 setup simply because among the setups I tried, this suits my preference well and it feels that it has better synergy with 400i than the other setups that I tried. The treble of the 400i in this pairing is smooth yet detailed and well extended, the treble isn’t airy but has good sparkle and definition, it doesn’t sound sibilant or harsh at all (except it is not well driven). Both attack and decay is quick making very agile even when playing complex tracks. Since it lacks airiness, the sense of depth, width and height isn’t that great the staging despite sounding realistic isn’t one of the most spacious cans out there, I find the closed back Beyerdynamic Dt1770 pro to be deeper and wider.

Sound Stage and Resolution

The sound stage of 400i is far from the best out there (Planars are not known for humongous stage) but I would say it sounds very real, imaging and layering is great and satisfying especially when playing tracks by Led Zeppelin, I can easily pin point the location of instruments in my mind. It sounds 3D-ish too when properly driven but still not as wide as D1770 pro maybe because the midrange of 400i is slightly forward and the treble lacks air too (Planars, duuuh). Resolution is nice too, I acquired the 400i for 7500 Php (150 USD) and it is one of the best buy that I’ve ever done in this hobby, bass region despite its quickness is very resolving, midrange is quite smooth but still resolves micro details, lastly the treble which has good sparkle packs a lot of details for the price.

Synergy and Sound Signature

Unlike other Planar Headphones, the 400i’s sound sinature ranges from warm and smooth to neutral instead of dark. Bass is a bit forward and is very quick, tight and resolving despite being smooth at the same time, the midrange is smooth and a bit forward in comparison to treble it has very natural timbre and sweet upper midrange that makes it a good gear for vocal focused tracks, lastly treble lacks air but offers good sparkle, resolution and speed to compensate. I suggest to use a neutral sounding DAP/DAC/AMP when using the 400i since the signature it has is flexible enough to tackle every genre you have in your music library.

Shanling M3s (High Gain, volume @ 90)

This is how I tried the 400i initially and it was my first headphone purchase, it sounds thin and the treble sounds metallic but still it is far better than any IEMs that I’ve tried under 30,000 Php (600 USD). Obviously it is not driven properly, the bass is still quick, mids sounds too dry but has natural timbre, the treble in this pairing is prominent and sometimes it is aggressive. Despite being efficient, planars are known to be power hungry but in comparison to SUNDARA the 400i requires a lot more power.


Adding Jazz R7.0 as amplifier and using copper IC, it sounded like a new gear. The bass extension became deeper, better texture and details and the mid bass became tighter and more controlled. Midrange gained a lot of body, it became balanced (enough lushness and transparency) the timbre became more natural due to added body, smoother yet resolving. Lastly the treble became smoother and less aggressive, sparkle and extension still remains the same.

Adding JDS Labs O2 (with burson v6 vivid) as amplifier and using copper IC, it sounded very detailed in comparison to jazz R7.0 and Shanling M3s (high gain), details on midrange and treble almost slapped me in the face but the overall tonality became thin and dry, it lacks body and I didn’t love the synergy.


Adding Periodic Audio Ni (double amping) as amplifier and using copper IC, It sits between the tonality of Jazz R7.0 and JDS Labs O2, the body is slightly reduced but it sounds more transparent than the R7.0, details are there but not as prominent as when I’m pairing it with O2. Noise floor is suprisingly low despite using it on PO and not on LO (the Ni doesn’t have volume control, same goes to the M3s when it is on LO so I have no choice but to use PO to be able to control the volume). Despite being small, the Ni was still able to power the 400i decently but among the three amplifiers, I’d pick the Jazz R7.0 because it was able to properly balance the lushness and transparency of the 400i.

Smartphone (Huawei Mate 10)

The Huawei Mate 10 has a sound signature of neutral-bright, sound quality far below the M3s, cranking the volume to 80-100 the sound of 400i is just decent compared to the SUNDARA, it sounds dry and thin to the point that male vocals doesn’t have sufficient body. I don’t recommend using it with smartphone alone cause you’ll get around 30 percent of its full capacity (soundwise).

Comparison

HIFIMAN SUNDARA

The SUNDARA is actutally the upgraded version of the HE-400 series, in terms of build quality I’d definitely pick the SUNDARA, the body is made out of metal and still maintaining it as lightweight as the HE-400i, the cable is better too it is less tangly than the 400i’s stock cable. The sound signatures of the SUNDARA and HE-400i are nearly identical except that the treble of SUNDARA is more relaxed. In terms of sound quality, the SUNDARA is definitely and upgrade, the timbre is even more natural, better tightness on the bass, wider and deeper sound stage, more transparent mids and smoother treble. Resolution is not night and day but still, SUNDARA picks more details and textures than the 400i, nonetheless for the 2nd hand price of the 400i it is still a good buy if you love the SUNDARA but can’t afford it.

Beyerdynamic DT1770 Pro

This is a dynamic driver headphone so obviously it has better staging and airyness, but lacks coherency, speed and transparency in comparison to planars surch as HE400i. Desptite being closed back headphone, the DT 1770 Pro sounds wide and airy, but for me the 400i seems to be more 3D-ish. Sub bass depth and weight easily goes to the DT 1770 pro while the tightness and speed of mid bass goes to the 400i. The midrange of the 400i and DT 1770 pro seems to be linear while the latter leans to be slightly recessed, transparency, timbre and resolution easily goes to the 400i. Lastly the treble of the DT 1770 pro wins in terms of airiness, resolution, and sparkle while the 400i snatched the speed and extension. Overall they are pretty close depending on usage, I can’t use the 400i outside of my workplace or house since it is an open back design and lacks isolation and sound seal.

Conclusion

This guy is my first love, I tried several Headphones before such as Sennheiser HD700 and AKG K712 but they never caught my attention the same way the HE-400i did. I love the timbre and how it scales very well with various amplifiers. Despite having pretty intimate sound stage for an open back headphone, it still sounds realistic since imaging and layering are top notch. Transparency is great as well while the resolution is just above average compared to other headphones that shares the price tag of the 400i. Despite being advertised as efficient planar headphone, it is not really meant to be used straight to your phone, adding some cheapo amplifier will make it sing a lot better than before. There are design flaws, bass isn’t the punchiest too, and the sound seal is far from being great but if you use it with proper source and place it is definitely a good buy.

ALL REVIEWS ARE CREATED BY SOULSIKREVIEWS.COM


VIDEO REVIEW:





Hifiman He400i on the wall mounted headstand

INTRODUCTION

Headphones are made of different types of drivers. Normally, it is made of dynamic drivers. If you pick up a random headphone from your nearby Best Buy, it’s probably going to be a dynamic driver headphone. Some headphones use different drivers to produce sound. This is mainly to produce a different or unique or better sound signature. The headphone we will be going over today is the Hifiman He-400i, a famous planar magnetic headphone, arguably one of the best headphones under $500. Planar magnetic headphones usually have larger thin drivers with more magnets on either side of the drivers. You can find more explanation of the difference between drivers online and we might provide you with one in the future but for now, the planar magnetic drivers are commonly found in audiophile headphones with companies like Hifiman and Audeze designing and selling them.

ABOUT HIFIMAN

HiFiMAN Electronics is a designer and manufacturer of audio products including headphones, amplifiers, and portable audio players. Hifiman is known for its high-end audio products made under the brand Mee Audio. Its most popular products include the HE-400 which are full sized open back headphones and the RE-400 which is an IEM (In Ear Monitor). Both products are supposedly critically acclaimed for their sound quality

DISCLAIMER

This review unit was provided by audio excellence (an audio store in Canada) with the permission of Hifiman distributor. As usual, my reviews will be honest and contain no bias.

SPECS

Frequency Response: 20 Hz – 35 KHz

Sensitivity: 93dB

Impedance: 35 Ohms

Weight: 370g

Cable length: 1.5m

Plug: 3.5mm/6.35mm

THE BUILD QUALITY

Headphone: most of it is made of high quality plastic with thin metal suspension. The headphone seems durable and comes with a case that seems incredibly premium. The headphone adjustment is made with a up/down clicking mechanism which feels nice and easier to adjust because you can physically see or feel how much you are adjusting for both left & right. This was a problem in the HD6xx/HD650, where there were no ticks/levels to know if you were adjusting the headphones evenly for both sides. The mesh on the side of the headphones are very beautiful and the drivers can be seen with the right lighting, of course, this open-looking mesh means, this headphone is very open back, both in terms of sound and leakage.


HIFIMAN He400i rear view

HIFIMAN He400i mesh
Pads: the stock pads are the Focus pads, with the velour on the inner part and pleather for the rest of the pads. This hybrid pad feels very nice and is extremely comfortable but gets a bit hot with extended wearing durations. It is also glued on, so you would need to make some serious modifications to change the pads. Some suggestions out there are the alpha pads, but this was not tested by me. For me, the stock pads were just fine.


HIFIMAN He400i Focus Pads. Velour side can be seen from this angle.
Cables: Fabricated and looks like a pretty decent stock cable but is only 1.5m long, which is very short for a desktop/home use. It also terminates in right angled jack, which makes plugging into your amps rather inconvenient. The connectors are 2.5mm connectors that is differentiated “left” & “right.” Clicks in nicely and it is firm enough that it won’t yank out.





Case: hands down, it comes in the most premium packaging in the world.

SOUND QUALITY

These headphones are highly efficient and can be even driven with a phone.

Low Freq: The bass in the He-400i is well extended. By that I mean, there is some sub-base. It is comparable to the sub-base I get when I use my HD6xx with the Dark voice 336 se tube amp, which is already around $800 dollars in value. The overall bass is intimate, tight and punchy. It is rather an accurate representation of bass but at the same time, very pleasant, in my opinion. The bass does not blead into the mid frequencies as much as in other headphones, for example; in the tracks, Smooth Jazz Tribute to Sam Smith, the bass came in nicely without taking anything away from the beautiful mid frequency presentations.

Mid Freq: This is a warm-ish headphone and I say that because this headphone sounds quite like my HD6xx from the low to low-mid frequencies and then it starts to differentiate itself from the high-mid to high frequencies. The Vocals are very clear and everything exists within the boundary of “mids” but there is no emphasis in any specific areas. Everything from vocals to instruments retain that smoothness through this frequency. For example; while listening to the Small Bump by Ed Sheeran, the bass was almost euphoric while the guitars and vocals retained its beautiful harmony

High Freq: this is where the real fun begins for this headphone. The highs are rather rolled off in the HD6xx/H650 or HD600s but here, the highs are clear and much more evident. It is much more natural and lively-sounding. Now, you might associate lively-sounding to bright or even sibilant headphones, so let me make it clear, “He400i is just right, it is not sibilant.” Now, of course if you are coming from a more dark-sounding headphone or if you are all about that “warmth” then, you may FEEL like it is sibilant at first, but that is just your ears getting adjusted to all the details in the highs that you have not heard before. Some instruments are meant to sound this way, to make the overall track livelier, but some headphones take this away because not many people enjoy all the details in the highs and it is a very hard to get that perfect roll off to make it “just detailed enough but not sibilant.” But as you move up away from the Mid-fi area, you are seeking for more “detail and clarity,” therefore high end audiophile headphones are commonly criticized for being sibilant. It seems like He400i has achieved that “just right” feeling for some people. It may be still sibilant depending on your preference or previous gear but at least for me and those I have talked to during this review, this headphone seems to do just that, “perfect.”

Soundstage: the soundstage is most intimate than the HD600 or the HD6xx/HD650, but this makes the bass much more apparent. This would be a preference thing but I enjoy soundstage and this was a downside for me

Imaging: very accurate for a sub 500-dollar headphone, I would say it competes with the HD600/650s if not just a tad bit better. For example; in my symphony tracks, I could tell which instruments were coming from which positions but it was not a wide accuracy but more an intimate one.

HD600/H650 vs HE400i: Straight off the bat, there is no clear winner, it will ultimately be your preference that determine which headphone is right for you. The HD600 is commonly compared to the HE400i. Some reviewers say that the He400i is as neutral as the HD600, which I do not agree with because if anything, the He400i is more closely related to the HD650s in that it has that bass. Of course, both do not have a lot of bass but they have more than neutral headphones like the HD600s. He400i sounds livelier than both HD600 and HD650 but vocals come in much more euphorically in the HD650s because it is much more present due to the rolled off highs. Some may rather prefer the more natural sounding vocals and instrumentation in the He400i.

He400i + phone: at max volume, the He400i is at a reasonable listening level. Everything sounds great but at the same time, sound a bit lean and messy/veiled in busy tracks.

He400i + Schiit stack: sounded just right, I can see many people using this combo as it adds more warmth and clarity. Modi 2’s clarity may be overwhelming for some people and can be even called sibilant in some tracks but again, this depends on your preference and which gear you are coming from.

He400i + Oppo ha 2 se: This was by favorite combo. Sounded phenomenal, even took it out for a drive in my car and although it may not have been the best idea, I have no regrets. The bass boost in the Oppo ha 2 se with the He400i is just mouthwatering. The mids became more emphasized with the highs retaining that clarity and detail.

He400i + Darvoice 336se: I’ve noticed some higher than normal noise floor, probably due to the He400i being low impedance headphones but this combo adds more bass and vocal emphasis. Overall, I would say it makes the He400i slightly warmer without losing any detail in the highs.

He400i + Jotenheim: Rather an overkill, since these headphones are highly efficient. But a powerful amp and a good dac adds more body to the sound making everything more full and detailed. With this specific combo, it felt like everything the He400i could accomplish was accomplished. The instruments and vocals sounded much more detailed compared to the He400i + phone combo. The bass also seemed to extend more and punch more confidently.

Overall Thoughts

The He400i is a great headphone to start with if you are looking for a great headphone. If you are looking for great headphone within this price range, it is either the HD600s, 650s, or these. It all comes down to what is important for you. Do you prefer more bass & lively/detailed headphones? Then, the He400i could be for you.

At 240 dollars new (price I paid) this probably one of the best price/performance ratios I can think of for cans of this class. Each song is a new listening experience and these sound far superior to any other cans or speakers I have ever heard. I am currently using a C&C BH amp Colorfly C3 combo. Sound is very addicting with very pleasant musicality with great tonal balance. Clamping force was high on initial use but they fit much more comfortably after a few days of use. I would gladly pay 400 even 500 for these headphones.

I'll keep this relatively short as the HE400i has over 20 reviews here, some of which are very detailed and some that contradict others. This is just my 5 cents on the matter.
 
I think @jerg summarized it perfectly in his review, that these are a "compromise between musicality and technicality". On one hand, they are detailed and accurate, have great separation and for acoustic music, there's good layering. On the other, listening through them simply isn't immersive enough, as if they are too detailed, soul left outside the box. It's kinda hard to explain in words, but if you ever get the chance to listen to a pair of Shure SE535 (*) or something with a similar audio profile, you'll understand what I'm talking about. Imagine the audio equivalence of drinking just enough to feel the effect.
(*) My listening (and evaluation) mule for the past 5-6 years.
 
Other than musicality, my second and final con on audio with these, is the treble. It's too extended, causing things like cymbals to sound too distant from the rest of the record (think one floor above). Some call it separation, I call it "the thing that's wrong with half the cheap headphones I listen to", except the HE400i ain't cheap. A lot of companies seem to do that as it adds sparkle and detail (I guess?), but personally, I'm not a fan.
 
Unto actual usage, these are pretty easy to drive from anything. Smartphones, Fiio amps, 1st gen Schiit Fulla, no problem.
On comfort, the pads and headband are very nice and comfortable, but the grip is very tight. I've been looking around for a solution on Google without avail, till I got tired (and pissed) and took the "manual" approach: Bent them myself at 5 points across the upper steel gate, now it's just fine (the 2 L bends, middle, and half-way through to the middle).
I read about these having some issues with the cable and Hifiman mentioned on their website about swapping them. For what it's worth, I got the new cable, and no complains. It's thick and conductive, really all I have to say. The 6.5mm adapter is crap though, had connection issues so I threw it to the bin (having another 5 laying around).
 
Lastly, Hifiman states in the manual that "to obtain optimal performance", these should be burned in for "at least 150 hours", constantly. Subjectivity aside, this is, by far, the dumbest remark I've seen on any headphone, from any manufacturer. Just think about the prospect of, well, buying a pair of $500 headphones, eagerly anticipating them, finally getting the package and then, "welp, here they are, let's just put them there playing and wait another week". By now I imagine I passed the 150 hour mark, and frankly? I don't remember how they sounded a week ago in comparison, to be bothered with. If it wasn't important enough to burn them during production, this can't be too meaningful at the customer's hand.
 
To close the review, you might be wondering why the 5 star rating. Simple: Supposedly these retail for $450, but occasionally they will go as low as $250, and for that price, it's very impressive value.

Equipment used: Schiit Modi Multibit and Vali 2.

I will keep this short.  I currently have both the HiFiMAN HE-400i and the Beyerdynamic DT880 250 Ohm non-pro version.  I read a lot of reviews with people bagging on the DT880 vs the 400i, so when I got the DT880 I figured that I would be sending them back and keeping the 400i.  I had been listening to the 400i first, and I really liked them.  I love the focus pads and the sound is really good.  I got them on sale, so they were a great deal.  As a matter of fact, I did not even plan on opening the DT880.  However, I decided to give the DT880 a shot.  
 
Well, after listening to both the 400i and the DT880, I am returning the 400i.  I used my on-board sound card to power these.  I listened to Deadmau5, Nora Jones, Metallica Enter Sandman, Steppenwolf.  I did a side by side comparison switching back and forth adjusting volume levels, and honestly the DT880s just sounded clearer to me.  The bass on the DT880 hits harder, the trebles and mids were clearer.
 
I was shocked by what I found after reading all these reviews.  I don't know if people are making some of this stuff up, or what, but after owning both and doing a side-by-side comparison to me the DT880 seemed better, at least for my taste.  They are also lighter than the 400i.  Don't get me wrong, I like the 400i, but compared to what I experienced switching back and forth between the two.... That being said, I would consider myself to be your typical listener.  I got the 400i for $249 and the DT880 for $149.  I am surprised, but I am sending the 400i back to HiFiMAN.  For me the DT880 is the winner.  I still think the HE-400i is a cool headphone.
 
 
Other headphones I have owned that are worth mentioning are the DT990 Pro and the ATH-M50X.

Would recommend if you are not a bass heavy person. This paired with the EF5 amplifier from Hifiman is almost majestic, music just flows extremely well. Soundstage also has improved from originals, which is extremely impressive, considering the originals being so great. Definitely recommend, have been disappointed by hifiman in anything.

Introduction: well, let me start off by saying that I don’t come from the wealthiest background.
So, it shouldn’t come to a surprise that purchasing the hifiman even at $300 was a big move on my part and wasn’t an easy decision, but my love for audio made me detest using cheap audio products which didn’t honor music, instead spat on its face.
 
 

Da luuks and da build: I’ll say it, these look sexy. The chrome cups give for a very classy and sophisticated look IMO which helps it segregate itself as a higher class of headphones. The headband is not so ideal but you get used to them. Others really don’t. I wore these during a road trip and I stopped counting how many weird looks people were giving me. It was awkward to say the least. But tell you what? I didn’t care, (maybe I cared a little bit), but I wasn’t going to take them off my head.
 
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But the sexy cups tend to be a fingerprint magnet, they don’t give me much confidence in terms of being scratch resistant. Take care of them will you? Try not to throw them around and be rough with them. The headband adjusters inflict scratches on the back of the metal structure. For the retail price of $499.99 this is unacceptable to me. Hifiman messed up big time in this part for me. The adjusters are very hard to adjust due to stiffness but ease up over time. The new 2.5 mm connectors look nice, I’d say they shouldn’t cause any problems.

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Da cumphorttt: Holy schiit! Why would you take these of your head? Even if no music is playing, I would rather keep them on my head while they hug my head with those soft pads. It’s not a headphone that I want to keep on my head just for its sound, but its comfort makes me want to keep them on even if there is no music on! I have listened to these for hours at a time and felt little to no discomfort. These don’t disappear completely but they don’t keep screaming “hey I’m on your head, does that bother you?”.

 
Da sundddd:
First impressions when I received them were as follows,
***note: I am playing them out of an Objective2 amp with no external dac, only the crappy one from my HTC one m8 and my Lenovo notebook. So maybe that's the reason for my impressions.
 
 Unimpressed. I simply didn't see what the fuss was all about. The treble siblant and strident.
 
 The vocals were nice but there was no *magic* I wanted for 300 dollars.
 
 The bass, oh my God, where is the bass? Is hifiman pranking me? Is this a joke? Are my headphones broken? The mid bass sounds horribly anemic, like someone beating on plastic with plastic.
Unacceptable for it's price tag. Where is the liquid planner bass I was promised? There is no sign of sub bass. It's just missing. On "secrets" by tiesto and kshmr- this particularly showed.
 I tried eq from dobly atmos on my HTC one m8: on the "rich" setting with a bit more eq'ed sub bass. better. The treble calmed down, but not much. The mids still there and are nice but no orgasmic *magic*. They are just not forward enough for me. Mid bass less plastic feeling but still not good enough. Sub bass is helping the mid bass sound a bit more textured but it's still mostly missing and obscure. Hell I preferred the punchy textured bass on my $50 status audio hd one than the he-400i at this point.
 
 But slowly they started to improve, (burn in? What? It really works?) the treble calmed down a lot. And the Objective2 seemed to help, (ampless directly from phone with eq didn't work well enough). The mids started to sound a lot more nice. Vocal layering was very impressive. The bass improved and wasn't as plastic crappy feeling anymore. But it didn't go deep at all. Impact was almost non existent. It wasn't "accurate" there was certainly information missing my $10 earbuds with eq can dig out that this couldn't.
 
 On a jazz track it really shined. On "the look for love" by Stanley Turrentine - the instrument separation was impressive. The instrument's attack and decay is something I first realized on this headphone. The strings and drums sounded fantastic. They had life in them!
 On "better than anything" by Diana Krall and Natalie Cole - the vocal layering and separation was also quite impressive as I've never heard them on other cheaper audio gear.
 But at that time I thought that if they didn't improve drastically with a better dac (garbage in, garbage out and all that), and further burn in, I’d have to say that I really didn’t think they were even worth $300 let alone $500. But prices are really crazy in the audio world I’ll have to say. My perception of value for money might differ from yours but whatever.
 

Now these are my impressions after listening to them for around a month-
 
Bass: amazing sense of realism and the lightness of the slam helps clarity.  It can sound anemic depending on the song and the rig. There is a certain texture the bass presents that I’ve come to love. With the correct eq however it can reach higher levels of awesomeness! For bass heavy genres I use the eq to bump up the bass quite a bit and boy does it seriously hit hard! Most of that seductive texture is still retained but now it doesn’t just punch weakly, now it attacks you with authority! Yes, in a pleasurable way! On The Eagle’s Hotel California the kick drums with eq are very authoritative and make for a very addicting listen.
 
Mids: Oh. Thissss. This is amazing. The mids have a sweetness to them that is hard to describe, its unlike anything I’ve ever heard. The instruments are presented in a way that is just a joy to listen to! On Porcupine Tree’s song- My Ashes, the guitar sounds incredible and the imaging is very good. The vocals carried that sense of dark atmosphere which just stood out so much to me! And not surprisingly Steven Wilson’s songs are great on these. The Vocals and the instruments never sound congested, rather they flow. Green day is also amazing here. The guitar riffs have a sense of authority to them. On Diana Krall’s Let’s Fall in Love, her voice sounds intoxicating to say the least. I’m blown away each time I hear that song. Bjork and Carpenters also sound amazing! Blowing me away each time I put their songs on.
 
Treble: One cannot be perfect from every angle. Somewhere there has to be a problem. In this case for me It’s the treble. Don’t get me wrong, it is very extended and isn’t veiled or dull in any way. Rather it’s insanely lively and clear. But that clarity can get a bit displeasure-able at times. There’s peaks in around 4k and 7-9k that I can only describe as party poopers. They almost ruined the headphones for me! They made the vocals sound shrill and harsh as well as the cymbals and high-hats. Listening to Fetty Wap’s Trap Queen without eq ,the cymbals/high-hats are ear piercing and make for a very very bad experience. On Eminem’s Must be the Ganja, it’s torture. Everything sounds sibilant to a certain degree. But I was persistent, after weeks of trial and error I finally came up with a eq setting for me, which killed all the sibilance. Now this headphone for me had become worth $300 and even more. Everything sounded smoother.
 
Soundstage/separation/imaging: wow, coming from super low-fi gear this was amazing to me. The attack and decay, the transience, the flow of everything was spectacular! The clear identity of each instrument and their ability to stand out individually without seeming to be mashed into a crowd was something I hadn’t experienced before until I heard the Hifiman he-400i. While the soundstage isn’t HUGEEE it has its charm for me. The soundstage over all seems to expand more on some songs than others. Vocal layering is also very nice as I had stated above in my first impressions.
Amping: This needs and I mean NEEDS a warm sounding amp to sound like what people praise these so much for! I had to learn that the hard way. I didn’t have the budget at the time to get a rig for it so I was stuck with an Objective2 double amping out of my phone or laptop and using the onboard crappy dacs they come with.
So if you’re thinking of getting these for portable use with a phone, like I was, you can say bye-bye to that. (unless of course you have a warm sounding amp/dac in your phone e.g the nexus 6p?).

Conclusion: Over all I wanted to experience what good audio sounded like and hifiman he-400i gave me a bit more to bite than I could chew. It’s overwhelming treble extension is definitely something I could live without! It’s sibilance and harsh/shrill attitude is something that ended up making me decide that this wasn’t really the right headphone for me.  
 
 
P.S- here’s the eq that I was using for them:
 

 
 
 
And for when I wanted BASSSS~
 

 
 
 
Please do let me know what you think of my review (as it's my first), where I messed up and where I can improve on in the future.

I am coming from limited headphone experience compared to most on Head-Fi, however I've had my fair share of listening to headphones over the years. I have listened to the following open back headphones: Senn HD-650, HD-580, AKG K712, AKG K240, Beyerdynamic DT 880, and Beyerdynamic T1. Out of all of these, I have to say I prefer the HE-400i over even the HD 650s, which were my favorite for nearly the 2 years I have had them so far. While I love the laid back sound of the Sennheisers, I could not really experience many of the "hidden" things in recordings and other details. The HE-400i's have a way of making instruments sound super realistic, and in my opinion they are amazing at instrumental and classical music. In some pop songs, this extra detail means slightly heightened treble because of compression and mixing for those rock and pop genres, however it is not so much that things become sibilant. Comparing to the Beyer T1, these have not nearly as bright treble, and I much prefer these over the T1s.
 
Bass extension is AMAZING on these. Sure I haven't listened to the other Hifimans or Audeze planars, but I have never experienced planar headphones before the 400is. Compared to everything I've heard, these win in bass extension hands down. They have the perfect amount of bass for me, I would call ever so slightly more than neutral, which I like. I just love the detail and the way they make things sound. The mids are great, but I do prefer the HD 650 mids over these. They are very close to the 650 mids, a little less smooth however.
 
I have 2 minor complaints for the HE-400i: the cable, and the fit. The cable terminated to a 90 degree angle 1/8th jack, which is very odd considering most headphones like this have a straight jack. But, the quality of the cable makes up for it, being completely cloth covered until the end of it. The fit for me is ok. I have a taller head than most people, so I have to click the headband adjuster all the way up for the pads to fully cover my ears. If the adjuster had one less click from the top, I would not be able to pull the pads down over my ears. So if you have a large head like me, see if you can try them before buying, because what's the point of having a headphone if it doesn't fit. The build quality however is extremely impressive, these feel more like $800 headphones than the $499 listing price.
 
If these sound so good, I can't wait to hear the HE-560s. I had my doubts about Hifiman before, but these guys are the real deal and make excellent quality headphones. I got these open box for $389, and even for the listing price of $499, I'd say these are well worth it. 

You’ll understand that once you start buying headphones, amps and dacs that you get the niggling feeling every once in awhile to try something new. Or to get the next upgrade. Well I purchased these during my niggly moment to do both.
 
I got these for about $450NZD which equates to $306USD as of this moment which is super cheap for a headphone of this build quality, let alone a planar from a reputable brand. I wanted to dabble into planar magnetic headphones and read great things about the HE-400i’s
 
Unfortunately I think I’ll have to let these go as they don’t really scratch the itch. This is not going to be an overly negative review just heads up
 
As you most likely already know, these headphones are low impedance and terminate in a 3.5mm jack which is angled. I don’t know about you, but I wouldn’t want to wear these outside. Luckily they do include a ¼” adapter.
 
Just FYI, I didn’t find I needed to mod the grills. My headphone didn’t actually come with padding inside so the sound was less impaired compared to some forums I had seen. I bought these second hand and I’m not sure if the previous guy took them out.
 
Build:
 
The build on this headphone is “O for Awesome” (NZ joke) need I say more?
 
Well since this is a review I will say more. The headphone is primarily made from metal, the cups are metal inside and out. The band is metal with nice tactile clicky tabs for adjusting. The only plastic parts are the yokes which I find a bit strange. I mean, the headphone is 2 pieces of nicely made metal with plastic joining them. Seems like a weak point to me. Anyways I digress.
 
The pads are also of good quality. My pair came with the newer version focus pads (Focus pad A’s). I believe the older versions were a bit thinner, but mine are very plush and comfortable. They don’t feel like memory foam, but are quite soft and feel decent.
 
The cables are very nice. The older versions had the old style screw on type connectors. However mine came with the detachable 2.5mm connectors on each ear. Much easier to take in and out as well as make replacements for. The cable itself is also well made with a braided exterior and decent thickness and pliability at the same time They are a much welcomed upgrade from the thin silver HE500 cables.
 
Comfort:
 
These are among the most comfortable headphones I’ve worn. I’d say even slightly more comfortable than the HD800s. They are extraordinarily light for a planar and the focus pads really just seal the deal.
 
Since they are so light, 370 grams. The thin head band doesn’t really matter. It is wide and can spread the weight evenly on your head without any one section pushing down to cause discomfort.
 
There is also a good amount of adjustment available on the headband. The very nice tactile feedback from changing notches is great and it doesn’t feel like it would change on their own without your say so.
 
One small gripe about the earcups. This really is just a nit pick. Since the yokes are so far out on the cup itself, when putting the headphone on there isn’t really a “correct” place to put your hands when holding them. I like to flatten out the ear cups before I put them on so they don’t have to rub on my face to flatten out themselves. The yokes make this very awkward.
 
Sound Quality:
 
When I picked these up I was looking for that “planar sound” I know there wasn’t going to be heaps of bass and I was fine with that. But I was expecting transparency, soundstage and clarity for days!! Unfortunately I might need to sell these and spend a little more to get that. This is definitely a good entry into planar.
 
Treble:
 
The highs on this headphone are in no way spiky or sibilant. They stop just before it gets too far. They are however very clear and precise. The word to describe these headphones is “fast” most dynamic drivers just can’t compete with the speed of planars. It doesn’t skip a beat. Listening to music with a lot of layered instruments is a breeze.
 
Mids:
 
In general the highs and mids of this headphone are slightly extended. These two areas are where the headphone shine. Vocals and instrumentals sound very detailed while wearing these.
 
Bass:
 
Now I know that planars in general have slightly less bass. But in my opinion these headphones were lacking a bit too much. They were ALMOST lifeless in terms of sound. They had plenty fn mids and highs but the warmth, if even for a little bit were not there. The sounds I heard for the low end though were very detailed and precise. They weren't that punchy the majority of the time.
 
Soundstage:
 
The soundstage on these were pretty good. Coming from the hD600s these far surpassed them. The transparency of the planar drivers and the earcup design were almost perfect. I’d say the soundstage was wide and had some back and forth to it. But the up and down directions were a bit smaller.
 
Imaging:
 
Very nice. With the accuracy of the drivers and deliverance of minute detail the imaging was very accurate.
 
Conclusion:
 
I PERSONALLY don’t think these cans are my thing. I was expecting a slightly warmer sound. I know planars can do it. But it seems this headphone was much more analytical for me anyways.
 
I can not fault the build or comfort at all. It is by far the most comfortable I have used. The pads are great, the overall aesthetic is very sturdy and tough looking. I like it
 
For this price range I think this headphone does a great job. But it seems like I need to spend a little more in order to get a more balanced planar.

There is not much I can add to the best reviews that have been written here but I must say I am very pleased with the HE-400i... specially when I have been using the Sennheiser's HD600 for so long and was convinced that those were the absolute reference headphones. So naive of me!
 
The HD600's are indeed good but the Hifiman's present the music with much more finesse and realism. So much that I opened my wallet and matched them with a brand new Burson Audio Soloist SL, which they prefered in detriment to my old Musical Fidelity X-Can V3.
 
I was lucky to made the purchase right after the new version arrived in Europe - equipped with the 2,5mm plugs - but to my disappointment (the only one I might add) the stock cable was so incredibly bad that I get scared for a moment. The cable completly ruined the SQ that I cannot even describe!
 
So I made a 3 meter-long Canare L-4E6S with Neutrik 6,3mm jack plug and a pair of 3 pole 2,5mm I found on Ebay (and WBT solder) and... WOW! Now this headphones can sing!!!!
 
Being so cheap why aren't this cable offered in the package in the first place?!
 
Highly recommended

HiFiMAN HE-400i:  A Low Cost Neutral Planar
 

 
SPECS:
http://www.hifiman.com/products/detail/178
Driver Type                       Single-sided Planar
Plug Type                         3.5mm with 7.5mm adapter ( dual 2.5mm into the earcups )
Cord Length                     1.5m
Frequency Response       20 Hz – 35 kHz
Impedance                       35 Ohms
Sensitivity                         93 dB / mW @ 1kHz
Weight                              370g
 
WHERE TO BUY / COST:
http://store.hifiman.com/index.php/headphones/he-400i.html
$399 new
 
OVERVIEW
Being familiar with planars from Audeze, Fostex, and MrSpeakers I want to report how the HE-400i from HiFiMAN stacks up. HiFiMAN aims at delivering a comfortable headphone with tight bass while still keeping the planar sound signature. They also strive for the HE-400i to be easily driven by portables and we will investigate the efficiency along with the acoustics.
 
The initial impression is that the packaging, headphone, and cable all make one cohesive bundle with the exception of the right-angled jack plug on the end of the cable. I see no reason for a right-angled jack plug. This and all of my other headphones all have a straight jack plug. It appears to be an attempt to make it more portable, but the headphones themselves are so large it is unlikely that anyone is going to wear these away from their home rig. HiFiMAN did replace the screw in connectors that attach the cable to the headphone with 2.5mm stereo jacks making connecting the cable a cinch. Yay!
 
AESTHETICS

First of all the box is really well packaged. Adequate foam is placed during shipping and the headphone is neatly tucked inside the shaped compartment foam so they do not bounce around during shipment. The accessories are minimal including a single cable, 3.5mm to 7.5mm adapter, and the headphones. It would be nice to see a 3m cable included that has the straight jack plug, but the short cable was not a problem for my desktop setup.
 
The finish is dark blue with a metallic sheen. The grills are free of defects and add a hi-end look to the headphone. The gimbals, temples, and headband are all cohesive and because the earcups can swivel to completely flat, fit issues are minimal. The headband and head-size adjustment systems are one of the best I have seen in any headphone. They are superior to headphones like AKG and Audeze because they are easier to adjust and simpler. The earpads are pleather with a thin ring of felt on the part that rests against the ear/head. This allows for some air venting and typically tightens up the bass. It also adds to comfort. The earpads are angled with the thickest part of the pad designed to rest at the back of the head tilting the driver towards the ear canal. The earpads can be removed by gently deforming one side and pressing inward towards the center of the earpad and then bending the pad slightly. This reveals clips that hold the pad to the earcup. With the earpads removed one can replace them with other pads and play with the angle. To me this was an absolute must because the default angle for the pads made listening too fatiguing because the angle was too direct for my ears.

 
ACOUSTICS
After a long listen I determined that the peak extending from 3.5 kHz to 7.5 kHz is too fatiguing for my ears without moving the pads around. I reversed the tilt placing the thickest part of the pads to the front and thus the thinnest at the back. This drastically mellowed the troublesome peak and made the headphone much more listenable. It also shifted the soundstage from a back of your head experience to a more speaker-like sound. The bass is airy and renders very low bass notes. The mids remain extremely neutral and the treble keeps its rolled-off nature. If the HE-400i is too fatiguing for you try flipping the pads. Pro Tip: Some positions are not favorable and tend to negatively color the sound. I found the best positions are with the thickest parts of the pads either to the front or back. Having them up or down alters the sound too much.
 
Unamped: With an efficiency of 93 dB / mW the HE-400i does need a decent voltage swing to get loud enough. To achieve 110 dB SPL a voltage of 1.3 volts RMS is needed which should be fine for most devices. Acoustically, portable listening is superb. The bass is crisp and tight, the mids clear and mellow, and treble well extended be it a tad rolled off in the upper-most frequencies. This slight roll-off makes for a more enjoyable experience by not being bright. The treble is not so rolled off to the point of being colored or greatly attenuated, just rolled off into good balance. Chick Corea’s Three Ghouls, Part 1 sounds very even from bass to treble. The chimes and triangle are easily discernible without being drowned out by the midrange and bass. The bass is airy and engaging. Perhaps a touch of air is removed from the woodwinds, but the track sounds excellent in all other regards with the HE-400i.
 
Amped: Amping the HE-400i reveals how inefficient it is. Right away I had to go to the hi-gain setting on my desktop amp. Almost all other headphones run on medium gain A good tube amp, like Schiit’s Valhalla 2, will further mellow the somewhat direct sound of the HE-400i and provide plenty of voltage into this voltage hungry can.
 
Being very neutral the HE-400i reveals flaws in your music. It will not enhance an already neutral sounding track and some music among my hi-fi tracks fell flat. Take Dion’s Crossroads from his Bronx in Blue album. The midrange is very harsh and hard to listen to. The mix is just that way on this track and with a less neutral can it can be hard to catch. Others like Benni Chawes’ Always on My Mind from the Bang and Olufsen concert prove sublime. The bass is clear, but not overwhelming, Benni's voice is up-front and delicate and the brush strokes on the drums clearly audible. Amped the HE-400i sounds better with electronic and jazz over rock and metal, but once your brain adapts to its sound signature it becomes very competent at just about anything you throw at it.
 
Switching to the other amp in my setup, the Grace m903, I found the HE-400i to be more detailed, smoother in the midrange, and equally even in the bass compared to the BUDA. The BUDA sounds a bit colored with the HE-400i having too much bass and not enough detail in the upper treble. This leads me to think that finding a great amp synergy will allow the HE-400i to sound even better, but any reputable amp will suffice as long as it can swing the voltage. In fact I found the HE-400i to sound great from portables and my desktop amps.
 
CONCLUSION
There is no doubt that HiFiMAN is coming out with some great gear. The HE-400 and HE-500 are old favorites in the planar community, but with the new releases like the 400i and HE-1000 it is clear that HiFiMAN is picking up on improving their already great sound. The HE-400i, with the pads in the stock configuration, proved too up-front for my tastes. Perhaps I am just sensitive to the 3.5 kHz and 7.0 kHz peak as others have not really picked up on this issue, but to me it is important to mention that the pads can be moved. I have found that there are very few stock headphones that perfectly match ones preference. No surprise considering even our physiology is different. That said applying slight EQ or in the case of the HE-400i moving the pads around fixed any problems I found. It is definitely an awesome sounding headphone. Due to its neutral sound signature be sure to allow adequate time for your brain to adjust.
 
I think HiHiMAN met the goals of making a light, easy to drive, improved sound quality headphone that many, like myself, will thoroughly enjoy.
 
LINKS
Measurements
 
COMPARISONS
I have received a few requests to compare the the HE-400i to the AKG K712 Pro.
 
The AKG K712 Pro is one of my favorite dynamic headphones and I am intimately familiar with it. Through several iterations of upgrading I found it to be the most revealing headphone under $800. It does fall flat on its face when it comes to aesthetics because it feels cheap and does not have a great headband adjustment system. The HE-400i on the other hand is has a better design and is more comfortable. The HE-400i rests perfectly on my ears at the appropriate level while the AKG sits low and too loose. Both headbands are very comfortable, but the materials on the HE-400i just feel better made and thought out. The cables are both nice with the HE-400i being much shorter. The AKG K712 Pro cannot really be balanced without serious modification while the HiFiMAN can be easily balanced which is a plus if you have a fully balanced setup. The AKG’s finish is not a fingerprint magnet like the HE-400i which I know a few of you will enjoy, but how often do you look at the outside of your headphones anyway?
 
Sonically the two are similar being somewhat neutral and mid-centric. The AKG is more tinny sounding in the midrange compared to the HE-400i. Both generate bass well with the AKG sounding more airy and open while the HiFiMAN quick and direct. What I love about both is how they reproduce horns, drums, vocals, and especially guitar. Listening to Something To It by Great Big Sea on their Rant and Roar album shows how each sounds even. The HE-400i on this track can clearly be dissected into its various components. Bass, mids, treble separate out nicely giving each a very speaker-like presentation. The AKG focuses more on vocals and scopes in on the airy details like the slight echo in the room and the reverb of the drums. The AKG muddles up the soundstage and makes it harder to enjoy each instrument separately. The upper treble is easily discerned with the HE-400i compared to the AKG because of the muddling effect. I prefer the HE-400i because it sounds like the more competent headphone and is much more speaker-like.

400i is in my world actually different beast to the old HE-400 and should have another name. HE-460 would be more suitable I think. The sound is much more balanced than the old HE-400 which makes it suitable for different stiles of music. The sound of HE-400i is very clean, transparent and life-like. Compared to much more expensive headphones it can get a bit bright and congested in the mids. This is only when compared to planars costing more than double its price. HE-560, the big brother, has a bit clearer (more refined) mids, better soundstage, little less pronounced bass and a tad more treble energy. Overall the sound signature is quite similar. I am not sure if the price difference ($400) is justified in this case. The little sibling HE-400S has a bit less bass extension, messier and less defined mids and a bit more treble energy (although 400i has a bit more detailed treble anyway). The price difference of $200 is not that big but probably worth the "extras" in the sound of 400i. 
HE-400i is a worthy headphone and a nice introduction to orthodynamic headphones.

HE-400i are real audiophile headphones with clear, clean sound and a quite affordable price that won't break the bank. The build quality is on pair with it's bigger brother HE-560 and actually even better in some details. Compared to the older models HE400 and he500 the difference in build quality and comfort is like day and night. HE500 was a great sounding headphone indeed but very uncomfortable. 400i looks gorgeous with their mirroring surface finish. The comfort is splendid with soft Focus pads and adjustable headband that will fit even the largest of heads. The cable is detachable which is great.
 
Some people have been complaining about Hifiman's cable and connectors. I actually think they are quite nice. The locking mechanism on the plugs is secure and eliminates the risk of cables falling off.
The sound of 400i is one of the best I have heard from any headphone up to €700 even beating some headphones more expensive than that. The bass is very accurate, textured and deep. The mids are very detailed and lucid. Vocals have lots of character. There is a beautiful feeling of intimacy and naturalness to the sound. The treble is finely balanced to the rest of the soundscape and very clean. The sound is actually nicely balanced across the spectrum. The soundstage is not that big but the imaging is spot on. There is a good amount of air around instruments and vovals.

All in all this is a superb headphone worth every penny. It is priced as mid-fi headphones but perform at the hi-fi level. Real audiophile stuff. Highly recommended!

I was quite blown away, having only listened to cheap IEM's until I finally bought the HE-400i.
 
On first impression, I noticed a brilliant forward texture this headphone added to the music. It makes listening very fun and enjoyable, as bass, mids, and treble all seem to come alive from the liveliness + body of this texture. I would think of it as the opposite of being "muffled," this headphone makes the sounds come out very strong with lots of presence and movement.
 
As for sound quality, I think it meets all expectation of an audiophile headphone. Treble is clear and neutral. Mids seem to be more of the focus, as they have a slightly more pronounced volume and realism, especially when listening to vocals you can hear great details in the voice. Bass is tight, focused, has lots of texture and impact, and depending on the music genre can be either just right or a little too quiet for one's tastes.
 
As for the negatives, this headphone has a small soundstage, which can be extended with the help of DAC's or other audio equipment and tools. Nevertheless, the imaging is very forward, so without a large soundstage some listeners could find it overbearing. I like my music to sound very intimate, so I personally don't think the soundstage is horrible, although I do think that it can still be improved greatly in order to bring out dimension and depth, as well as overall ambience in the music.
 
What I personally strongly dislike about this headphone is its lack of instrument separation in busy tracks. Normally the separation can be heard quite clearly in most songs, but since I love music with a lot going on, I was disappointed with the performance the HE-400i. Perhaps it is because of a small soundstage or a lack of layering, I'm not sure, that contributes to certain sounds often being "drowned out." Instead, it sounds like a mesh of instruments and sound effects that I can't quite make out individually, say if I wanted to focus on a particular instrument that was playing in the background. I'm guessing most people will not have a problem with this however, as my music tastes are rather particular.
 
Lastly, the physical quality of the HE-400i is overall not as good for an expected $500 value headphone. Adjustment of the bands don't feel very smooth or well-made, attachment of connectors is awkward, and the box it comes in has lost adhesion in the glue. These minor issues don't detract any value from the headphones to me however, as I personally don't find them to be detrimental to my listening experience. I have only taken a star off for lack of instrument separation in busy tracks, which is something very important to me.
 
In conclusion, if the soundstage/layering problem can be overlooked for you, this headphone wows in every other way.

These headphones will let you know if your source is good or not.  I won't repeat much of the pros and cons of this headphone that hasn't already been said.
 
These are really comfortable for hours at a time, both in ergonomics and sound.  Bass goes deep, Mids are nice and Highs are sweet.
Bass doesn't have impact until you use an EQ or other sort of sound processor, along with a good amp.  I drive mine through an old school NAD 2140 amplifier.  I drive these hard enough for the grills to rattle.  Some of the stuff I listen too just isn't produced right and the Hifiman will reveal it to you and shove in it your face. Hence why I use an EQ and such.  Because without them, the 400i will make you start to hate some of your music selection.
 
Bass goes deep and has lots of detail.  Shove some good power through the 400i and enjoy the good head massage these planar drivers can produce.  And don't forget the nice soundstage that these open headphones have.
 
Comfort is as good as the HD650.  You can easily forget that you have them on and the hours just fly by.  Now if you want to hear manly bass, the HD650 isn't for you.  The HD650 is the Prius, whereas the 400i would be the Aston Martin when you consider the power capability between these two headphones.  The HD650 will hit its driver limit with a FIIO E12A!  That is just sad.  Pardon me, while I wipe a tear......from laughing.
 
Are there better sounding headphones out there?  Yes sure.  But you will spend way more money for a little bit of gain. But that is just my opinion and the complain box is already full.
 
Personally I don't think these are worth 500 bucks.  More like 400 max and that includes the box it comes in with.  
 
 
 
3/1/17 update:
I've put the JVC SZ-2000 "protein" earpads on the 400I.  Impact greatly increased and the total sound changed for the better.
 

 
Below are my current EQ setting on the DBX goRack

 
 
Foobar VST settings.

A little background before I start. I'm 16 years old and I slowly began to become addicted to fine, audiophile-quality headphones. I remember the first time I heard beats at an apple store. I thought they were amazing until I heard my friend's HE-400. Those blew me away and my whole perception on sound and music became a deception. So my journey is as follows: Audio Technica CKM500, Audio Technica M50, HiFiMan HE-400, and now HE-400i! Since I've owned the HE-400's before getting these I'll do a little comparison as well as an in depth review.

The type of music I listen to is usually EDM, POP, ROCK, sometimes classical, sometimes oldies like 60s, 70s, 80s, and 90s music. This may play a role in my review. My set up is Mid 2012 MacBook PRO with retina display>schiit vali>cable pro freedom upgrade cable> he-400i. I have tried these with a Geek Out AMP/DAC and I'll get more into that later and I'm about to acquire a schiit modi DAC.

Bass: The bass on these are in a word, stellar. My god...my mind gets blown away every time I listen to heavy bass music like Zenith by Dannic. On songs by Lindsey Stirling (Transcendence or Electric Daisy) the bass creates such a pleasant sound I start to question reality. It's just so involving! Now, both the HE-400 and M50 have more bass impact and slam but not the same amount of refinement. The bass on HE-400 and M50 bleach into the other parts of a sound spectrum. Bass on the HE-400 and M50 along with the V-shaped frequency curve created the fun factor but these are different. They just do their job and reveal what needs to be revealed. There's no exaggeration or emphasis without reason. On songs that call for bass, these deliver. I know these won't satisfy hard core bass-heads but are more than ample for your average guy. The first thing I noticed with these from the HE-400 is how much less slam and impact they have but with enough time I realized that it's actually a good thing. For slam and impact: HE-400 (9) > M50 (8) > HE-400I (7)... But for refinement and accuracy: HE-400I (9) > HE-400 (8) > M50 (7)

Mids: I'm sure you guys have heard that these are quite neutral sounding headphones. But in my opinion these are on the fence on a lot of aspects. I find that the HE-400i somehow stand on a fine line between being neutral and a warm sounding headphone as well as a fun and boring headphone. Mids on these evidently more forward than both the HE-400 and M50. The mids on these are nice; however, on certain songs things do sound a bit congested and a little recessed. With enough experimenting, I found that this can be fixed through adequate amping and cabling also helps. On the Vali and stock cable, I find things congested. However, on the GEEK OUT 1000 with the freedom cable the mids on these are just so amazing. Listening to new POP songs like "Want to Want Me" by Jason Derulo and "I really like you" by Carly Rae Jepsen really shows how the mids on these headphones are spectacular. Mids on these cans are the most pronounced and my favorite part of the headphones.
Mids Rating: HE-400i (9) > HE-400 (6-7) > M50 (4-5)

Highs: The treble on these things is a beast. They really do sparkle and listening to certain songs over again can be a revelation. When I listen to my Kenny G album or acoustic/classical music, certain instruments just find a way to pierce my soul and heart. It's just so awesome. I can't find anything wrong with them. The treble spike present in the HE-400 is now gone and treble on the M50 were just average compared to these. There is no spike in these. They just do what the should.

**I know that I've made these sound like perfect headphones but they aren't......... some things I disliked about these are below**

Cable: The stock cable is extremely light and fairly short (5ft) for some people, but I didn't have a problem with them for my set up. Switching to the upgrade Cable Pro Freedoms ($200) I realized how much detail I've been missing. The cable makes the headphones more neutral (more forward mids, more tube-like bass, and less harsh highs). So many things were heard which were absent in the stock cable. Instrument separation is also better on the Freedoms. The biggest things that the Freedoms did was add to the soundstage. There is a sense of realism and you are there experience. It's 3D. I personally think the Freedom was an exceptional upgrade and a must for anyone buying these headphones. They are $40 cheaper at Todd the Vinyl Junkie check it out.

Soundstage/Imaging: Soundstage on these are terrible. YES! I said it...terrible. They were so bad I almost thought about returning them for my old HE-400. I did however found a way to fix this. The cable helped a lot as well as a proper DAC. Geek out 1000 are sufficient to make the soundstage manageable. These headphones alone sound almost like a closed back headphone and it's the one thing I wish HiFiMan could have improved on.

Product: The actual product feels somewhat cheap being a $500 headphone. The headband adjustment system makes a cheap noise whenever I adjust it and I lack confidence in it. The ear cup grills rotate when I touch them and it isn't stationary. These problems aren't noticeable unless you are a meticulous person and shouldn't really bother you.

In conclusion, I believe these are perfect for anyone looking to buy a mid-fi headphone. They work great on a wide variety of genres. They only thing is you must have a proper set up and cabling is recommended. The vali makes the headphones sound fast, but somewhat dry and congested. The Geek Out make the mids sparkle and enlarges the soundstage. The cable pro freedom does so many wonders. If you are choosing between these, HE-400, or M50, then go for these please. Now, if you already have an HE-400 I wouldn't recommend shelling $500 for these. If you have the M50 then yes these are a worthy upgrade.

HIFIMAN HE-400i REVIEW
 
 
INTRODUCTION
 
 
First of all I would like to stress this is purely subjective review of HE-400i as I am now an biased  owner of these cans and my experience with headphones is limited. Nevertheless I have heard some of the better headphones on a decent rig and thus will try to compare HE-400i with other cans as that might be helpful to give you a better perspective of what HE-400i may offer. First time I heard these headphones was during the December 2014 in Bratislava (Slovakia). Thanks to a very kind reseller, I had an unique OPPOrtunity to listen and compare a set of high quality headphones such as Hifiman HE-6, Hifiman HE-560, HE-400i, Oppo PM1 and Sennheiser HD800. The source was MacIntosh MCD 1100 CD/SACD player, the headphone amp was Oppo HA-1. The session lasted for 2 hours, I was making notes and  decided to buy HE-400i. My previous headphones were Beyerdynamic DT990 Pro. My home rig is quite modest, I use HE-400i with a laptop and Audioengine D1 as a DAC/head amp or with my iBasso DX90 player. Other quality cans I have heard and compared (but this time without the possibility of a direct A-B comparison) with HE-400i include Audeze LCD-X and Audeze LCD-2 (fazored 2.2 version). I listen mostly rock, hard rock and pop, occasionally classical and metal, and rarely blues, jazz, new age and electronic. Recordings that I used for this review were approximately of  90% of lossless formats (flac, wav, ape, dsf ) , other 10 % were mp3s (from 192 to 320 kbps).
I decided to give a certain score to various aspects of HE-400i, 10 of these aspects refer to the sound, while few others refer to the non-sound related qualities like appearence, comfort, efficiency, value etc. All aspects have range from 1 (the worst grade) to 10 (the best grade). Virtually the perfect headphone (for the sound alone)  would naturally be 100/100 in my scale book (haven´t heard such one yet Because of that I decided to give HE-400i two kinds of score. The first one is just for the sound alone and the second one is my overall score (it includes both sound related and non sound related aspects) of the product.
 
DISCLAIMER
 
Please bear in mind all grades (used for both sound and non sound related aspects) are based on my subjective opinions. As I am an owner of HE-400i and my experience with other compared headphones has been relatively short,  my opinions might be biased or inaccurate.
I am not an expert, I just wanted to share my thoughts on HE-400i.  HE-400i had more than 150 hours of burn in, at the time of this review. With the exception of Beyerdynamic DT 990 Pro (which had about 200 hours burn in) I don´t know how much burn in had the other headphones to which HE-400i has been compared to in this review. My HE-400i was reviewed in stock form ( as well as all other headphones mentioned in this article.)
 
SOUND  ASPECTS
 
 
1) TIMBRE  AND OVERALL  TONALITY
 
 
HE-400i is a headphone with a very balanced sound signature, nothing really stands out, although in comparison to other cans HE-400i is significantly warmer than DT 990 and less dark than LCD-2. Overall I would say HE-400i is neither dark nor bright headphone.  To me the sound signature is neutral/ slightly warm what also happens to be my preference. As for the timbre - vocals and instruments sound naturally across all the frequencies. There is a slight dip in the upper midrange /lower treble (around 1 to 3 kHz) and then a slight dip between 4-5 kHz , but this is OK for me and might be even beneficial because it helps to avoid unpleasent shrillness, wonkiness or sibilance (especially in less than stellar recordings). Bass extension as well as treble extension is fairly decent  (http://www.innerfidelity.com/images/HiFiMANHE4002014.pdf)  and that is certainly helpful for the headphone to sound considerably realistic. Of course there are even better headphones which are able to portray vocals or instruments in even more realistic way ( e.g. LCD-X or HE-6). But to me these differences are actually subtle and thus would rate HE-400i in this regard (timbre + overall tonality) very high.  Positives in HE-400i tonality are obvious from the very first listening - you get typical planar qualities also in these entry level orthodynamic headphones such as: smoothness, linearity (no unnatural bumps or dips across the frequency range) and overall transparency. Other aspects which I like on HE-400i tonality and which are maybe a bit underappreciated are also 1) non-fatiguing and 2) practically sibilance free sound (this is by no means an integral part of a high quality headphone – for instance HD 800 is a tremendous headphone, but with its huge soundstage and analytical kind of sound it tends to be far more fatiguing and prone to sibilance than HE-400i). So despite being a bit behind in „realism“ in comparison to top cans (HE-6, LCD-X, HD 800) HE-400i gets in this section  (overall tonality/ timbre) due to its listener-friendly, well balanced sound,  a high grade:   9/10
 
 
2) BASS
 
 
Bass quality is usually a strong point in the catalogue of „planar virtues“ and here HE-400i delivers too: tight and punchy bass response, impressive texture and solid extension are adjectives which come to mind when thinking about bass on HE-400i. Initially I found the bass impact a bit softer on some songs but that impression was largely affected by the fact, that I used to listen music a lot of years through my vintage SonyEricsson W810i phone with the option „megabass“ happily turned on and...with some „bass heavy“ IEMs happily on, as well. Oh well... Being spoiled with such „bass treatment“ for so long, no wonder some ugly basshead took its toll... Yes, there are headphones with better bass extension, viscerality and better bass impact than HE-400i – for example Audeze LCD-2, ( which have some of the best bass I have ever heard)  but HE-400i still offers the bass that I would call „accurate“. Probably not enough weight for „ bassheads “, but certainly a plenty of punch or slam when the recordings call for it and all that with the beautiful, trademark Hifiman texture – overtrumping even Oppo PM1 in that regard, dare I say. When I was listening some of the SACDs (e.g. dsf files via iBasso DX90), namely Sting´s bass guitar on The Police album Synchronicity, I never had a feeling that I am missing something from the bass line. Especially on SACDs I found the bass quality from HE-400i outstanding. Also on headphone amp from Oppo (HA-1) or Audioengine D1 the bass came alive, particularly on lossless material. The situation was a bit different when you were listening mp3´s – there was less viscerality, worse layering, less bass oomph.  Subjectivelly speaking, due to the planar nature and gentle mid-bass hump I found the bass on HE-400i even more engaging and musical than let´s say the bass on HD 800. And after listening to some well recorded SACDs or other lossless files, I ´ve got a better idea how able is HE-400i to produce high quality bass. It´s pretty capable.  9/10
 
 
3) MIDS
 
Midrange on HE-400i is very transparent and yet, at the same time musical, which for me is a rather attractive (and addictive) combination. Particularly the lower midrange is sweet and very pleasant to listen. The mids on HE-400i are indeed richer/lusher sounding than the mids on HE-560 and it was one of the reasons I decided to buy HE-400i instead of buying HE-560. Vocals ( especially male, but female too) sound stellar, you can feel the emotions emanating from the singer. Vocals seem even slightly forward (although this depends also on specific recordings) and as such HE-400i is a very fitting headphone for vocal genres (rock, pop). I like melodic rock a lot and that´s why for me it is very important how capable is headphone to portray electric guitars – here on HE-400i the guitars (both electric and accoustic) sound great. It has just enough crispness/edge to sound lifelike and just enough smoothness to sound ear-friendly. Guitar grandmasters like Eric Johnson or Joe Satriani sound simply fabulously. Even on bad recordings these instruments never sound too screechy, which happened to be the case with DT 990 (and to a degree with HE-560). Other instruments like piano or keyboards also sound very naturely. But as some top cans have even more midrange creaminess (LCD-2), glamour ( Oppo PM1) or bloom ( HE-6) while maintaining midrange transparency on par or even slightly better than HE-400i, I decided not to give here 10/10, but 9/10. But nevertheless midrange quality is also a strong point of HE-400i sound and is really close to the very best headphones.
 
 
4) TREBLE
 
 
Treble on HE-400i is reasonably extended with a gentle spike around 9-10 kHz, which for me provides just the right amount of sparkle. There is less treble energy on HE-400i than on HE-560 or DT 990 but a bit more than on LCD-2 or Oppo PM 1. Cymbals, percussions, organ or string instruments like violin sound detailed and clear. There is no exaggerated focus on treble (like on DT 990) which may result into analytical tonality and fatiguing sound. Some headphones somewhat artificially boost treble which can give a listener sense of ultra detailness but usually such headphones  (like DT 990) have V-shaped sound and that is not my preference. On the other hand HE-400i doesn´t sound artificial in treble but quite natural, sufficiently detailed and smooth. Treble is well integrated with other parts into frequency spectrum and contributes to the balanced tonality of HE-400i.  OK, there are headphones which have slightly more detailed and still perfectly natural treble, namely HD 800 and HE-6 (these two headphones have the best treble I´ve heard so far), but on the other hand HE-400i offers (at least for me) sufficient treble oomph without harshness or sibilance. Sibilance or treble harshness/hardiness may occur very very rarely and only on pretty bad recordings ( usually badly mixed,  highly compressed remasters in mp3 format) On decent recordings, even on compressed, modern date music with poorer dynamic range, there is virtually no sibilance or excessive glare. I am sorry for a comparison to speakers, but my Dynaudio Focus 110A (1800 € expensive) are in no way so forgiving of poor recordings while Hifiman HE-400i is in that regard much more listener-friendly audio product. What already sounds harsh or overly bright on my speakers is still perfectly listenable on HE-400i. Among headphones HE-400i is more forgiving of bad recordings than DT 990, HE-560, HD 800 or HE-6. In my opinion it even rivals LCD-2 (fazored) and is only slightly inferior to Oppo PM1 in this regard. This is also one of the reasons why HE-400i has non-fatiguing sound and why I am giving such a high grade also in this section  – 9/10.
 
 
5) SOUNDSTAGE
 
 
Regarding the soundstage of HE-400i, there has been written certain criticism here and there on the internet. This criticism I can understand but can not fully agree with. I will admit that the soundstage is not the strongest point of HE-400i sound presentation but I can´t agree that it is any small, average or even claustrophobic. If that would be the case, then you simply could not have such an amazing instrument separation, which is somehow presented in HE-400i sound. Maybe part of this criticism came from comparing HE-400i with HE-400, in which HE-400i, perhaps, came up short. I haven´t heard HE-400 so I could not compare both headphones but I could compare HE-400i thoroughly with DT 990 and at least briefly with other premier cans. And I came to a conclusion that the soundstage on HE-400i is, as a whole, realistic and reasonably big. From my point of view, the soundstage width really is not exceptional, it is about on par with DT 990, but in height and especially depth HE-400i has significant edge over DT 990. This results into more 3D sound in relation to DT 990. From the brief comparison with HE-560 I did not feel that the more expensive headphone had here such a big upper hand.  I might be wrong though, because as mentioned, my time with (A-B ing) both headphones was limited. From my memory Oppo PM1 also did not seem to have much advantage here over HE-400i (and if at all, then probably in depth). Only when I heard cans like HD 800 or LCD-X it became obvious that there was substantial difference in soundstage expansiveness. However, what I like on HE-400i soundstage is that it comes natural and realistic: compressed mp3s with low dynamic range will truly sound narrower in width and generally flatter, high quality recordings (e.g. 24 bit/192 kHz FLACs or SACD files) with a decent dynamic range will sound a lot more 3D. Or, to put it in a different way, when the song is recorded with an expansive soundstage, HE-400i will clearly show it, without breaking a sweat. Bottom line: HD 800 is getting 10/10 here, HE-400i is getting 8/10 here, DT 990 is getting 7/10 here.
 
 
6) IMAGING
 
 
Imaging on HE-400i is pretty good.  It´s easy  to pinpoint where instruments or vocals are located, because of the reasonably big soundstage and great instrument separation. But it´s understandable that some  higher end headphones with larger soundstage, better treble and bass extension and slightly better overall resolution/clarity (e.g. HD 800 or HE-6) are able to offer even more precise imaging.  But HE-400i is no slouch in this regard.  Although HE-400i is on the „warmer side“ of neutral  I do not feel  it lacks airiness or speed. Despite having more intimate soundstage and less airier sound than HE-560 or HE-6, HE-400i is - thanks to its excellent instrument separation, solid speed /PRaT and resolution - still able to image really really well.   8.5 /10
 
 
7) INSTRUMENT SEPARATION
 
 
One of the sound aspects which in my opinion draws a line between average, good and great headphone is the instrument separation. ( Indeed, what else should „separate“ it, if not the instrument separation ?! )  In this context I would rank HE-400i to the group of great headphones because one of the things which a listener immediately notices is how easy HE-400i separates single instruments, main and background vocals. HE-400i is able to stay focused even during the busiest musical passages. This ability is naturally further enhanced by high quality recordings and high-grade rig. HE-400i takes full advantage of high quality lossless material like DSF/DSD files.  Separation on SACD type of audio files is particularly impressive.  Also for modern compressed rock/metal recordings is HE-400i a fully-fledged headphone as far as instrument separation goes, but here HE-400i clearly shows the drawbacks of recordings with poor dynamic range.  Highly compressed nowadays albums with a dynamic range under  7  -  in a direct comparison with older recordings - usually sound flatter,which negatively affects subtle nuances left in music. From my point of view, this is also harmful for presenting instrument separation in an effortless way. However, you can´t  blame the headphone for not making compressed 320 kpbs mp3´s sound like SACD files with a dynamic range of 12 or higher... I can imagine that some higher end cans like HD 800 or LCD-X would - due to their better soundstage, better treble or bass extension - sound more effortless in this aspect and that´s why I´m giving 9/10 here.
 
 
8) PRaT
 
 
I have to admit, this term was initially new to me and only thanks to this site (http://www.head-fi.org/t/220770/describing-sound-a-glossary and http://www.head-fi.org/t/371771/what-is-prat)  I became familiar that it is an acronym for pace, rhythm and timing. That´s fine, but what is it actually supposed to mean ?!  I´m not going to reinvent the wheel by saying that it obviously is connected with the headphones quality to present music in its full dynamics, in its ability to appropriately render even subtle, „ hidden“ microdetails such as decay, texture, attack (see the aforementioned glossary) etc. I came to an understanding that to have superior PRaT it is essential to have high quality transducers - which provide  excellent damping (to prevent resonances), fast transient response (to achieve superb resolution) and extremely low distortion. To make it short, HE-400i does have all of this... to a certain level, which seems to be (at least for me) rather high. Thanks to the planar nature of the HE-400i transducer, these cans are able to „ decipher “ also such „ hidden“ microdetails like decay or texture considerably quickly. This show ups in an articulate sound which is presented in HE-400i across the whole frequency spectrum. However there are headphones which are even more agile in this ability to portray attacks, with even better transient speed, leading to a more precise sense of timing in music and generally better resolution. I haven´t had a pleasure to hear electrostats but these are said to have that special agility ( thanks to the nature of their transducer). There is no reason to be doubtful here. The best headphones in this regard (PRaT), from the cans that I´ve personally heard, were the Audeze LCD-X. First think that struck me when I heard them was: „wow, what a fast sound !“. They were incredibly dynamic sounding cans through their balanced stock cable. But despite having a bit more relaxed sound than LCD-X on the balanced cable (which from my impressions is enhancing, besides other things, particularly the PRaT factor) HE-400i consistently offers, already through the unbalanced stock cable, a very fine sense of attack, fast decay and solid transient speed, that´s why I´m giving   8.5/10 here.
 
 
9) MUSICALITY
 
Probably the most difficult sound aspect to measure - if it´s any possible - is „musicality“. What is this so called „ musicality“  all about ? Well, for me it is quite subjectively perceived sound quality usually connected with a sense of cohesion, ability to present music as a whole, or in other words, great reproduction of macrodetail. It´s a sound which is „pleasent to ears“, often perceived as lush or euphonic, or sometimes kind of coloured in a subjectively postive way. This is the area where HE-400i truly shines. You simply stop checking or analysing every single microdetail and instead you feel „immersed into music“. With HE-400i you can clearly feel how much emotions are left in music, let it be passion, joy, sorrow, softness, regrets or commitment. Slightly warm/neutral sound signature of HE-400i is also very fitting for longer listening sessions. Up to this time I´ve heard only 2 headphones with maybe a touch more „musical“ approach, namely Oppo PM1 and the „pesky“- „ how could they make such a relaxing sounding can with such an „unrelaxing“ comfort ?! “-    LCD-2. These two cans would get 10/10 for musicality, while HE-400i gets 9.5/10 here.
 
 
10) OVERALL TRANSPARENCY/ RESOLUTION
 
 
Last, but certainly not least important sound aspect I´m going to briefly analyse in connection with HE-400i is the overall transparency and resolution of the headphone. These sound aspects are closely linked, and while they are not absolute synonyms (see http://www.head-fi.org/a/describing-sound-a-glossary), it´s obvious you can hardly have great transparency without having great resolution and vice versa. Headphones with great transparency (should) have optimal clarit, low distortion and sound free of significant peaks or unwanted resonances. Headphones with great resolution (should) have superb detail retrieval, ability to render even subtle information in music. As mentioned in PRaT section HE-400i have appreciably fast transient response which helps a lot in deciphering subtle details. Together with impressively low distortion across the whole frequency spectrum (see THD graph on http://www.innerfidelity.com/images/HiFiMANHE4002014.pdf) and generally smooth and cohesive „planar“ sound, we get, in my opinion, a headphone with a high grade overall transparency/resolution. However some headphones may have more accentuated or extended treble, which may lead to a sense of more detailed sound. Some listeners may prefer this and it´s usually a desirable quality for some genres like e.g. classical. Some headphones may have better bass extension (HE-560, LCD-2, LCD-X) with similar or better transient speed and that also leads into more detailed or textured presentation in bass/ sub-bass.  On the other hand HE-400i, also maybe due to its warm/neutral sound signature, does not feel overly analytical. It does not present music like „all details are in your face“ but chooses more musical approach – it tries to present music as a whole, while keeping more than sufficient clarity. At least for me. 9/10.
 
 
That is for the sound – related aspects...
Now briefly to the non-sound related aspects...
 
 
NON-SOUND RELATED ASPECTS
 
APPEARENCE / DESIGN
 
 
HE-400i are in my opinion very nice looking headphones. They have modern look with a newly designed headband and specific FocusPads (combination of velour and pleather) Cups are of a very attractive deep purple/ deep grey colour (depends on light and angle you look at). Only drawback seems to be they are a bit fingerprints prone so I would recommend to clean them regularl, if you want to keep them intact. I like the appearence/design of these headphones very much. But, be aware: If you look at yourself in the mirror wearing them, you may look as an alien from a very distant galaxy...  As known, HE-400i are of open back design and as such they naturally leak a lot of sound.
My score: 9/10
 
 
COMFORT/ ERGONOMICS
 
 
The construction of HE-400i feels rather solid, but the headphone is quite flexible in a positive way, as you can easily adjust the position of these cans on your head. After you place them on your head they stay firm and stable. New headband and Focus Pads are in my opinion also contributing to a better overall comfort. Some users have reported certain unpleasentness from the clamp pressure but I personally find it fairly comfortable. I´m a fan of FocusPads too, they are soft and pleasant to wear as your ears don´t get hot. Biggest impact in comfort department (in relation to the older Hifimans or other planars)  was obviously achieved by weight reduction. HE-400i, being at 13,05 ounces or 370 grams, is substantially lighter than the older Hifimans (HE-500, HE-400, HE-6) or Audeze LCD- series. This contributes (and in a big way) to a very good overall comfort of HE-400i, which is miles ahead against LCD-2, about on par with Beyerdynamic DT 990 Pro and a bit worse than on Sennheiser HD 800 (probably the most comfortable headphones I´ve ever worn)  As far as other ergonomics goes I did not find anything particularly bothering, besides of the cable connectors which are not the easiest to screw and the length of the cable, which might be a tad short ( only 5 feet or 1,5 meter long, but of a very good quality)  for a comfortable home listening - especially if you are using HE-400i with your main audio rig.
Summary: wearing comfort 8.5/10, other ergonomics 7.5/10   Overall comfort/ergonomics 8/10
 
 
EFFICIENCY
 
 
HE-400i are one of the most efficient headphones among planars. Their relatively mediocre sensitivity ( SPL at 93 dB/mW ) and low impedance (at 35 Ohms) mean these headphones should sound sufficiently loud and reasonably well also through a cell phone or an iPod. However, it does not mean HE-400i needs no amplification. It is still harder to drive than the average over the ear headphone. You would get much better results by using headphone amplifier. I´m using HE-400i with iBasso DX90 and Audionengine D1 (DAC/headphone amp).  Built in head amp in iBasso DX90 is sufficiently powerful to drive them to the high level even on medium gain. HE-400i is even touch more easier to drive than DT 990 ( SPL at  96 dB/mW and 250 Ohm impedance). With HE-400i I can get comfortable listening at 210-225 volume level on medium gain on lossless material of good dynamic range (11 and higher, usually older recordings from 80´s). With DT 990, in comparison,  I have to crank the volume to around 220-235 level with the same recordings. When listening louder modern recordings (lower dynamic range) the volume level around 195-210 is usually sufficient for me.  Audioengine D1 is also capable of handling HE-400i. It´s not the most powerful amplifier but it has no problems to drive these headphones really well. Overall I would say Hifiman HE-400i is quite an efficient over-ear headphone and can be also used with portable players.
My score: 8.5/ 10
 
 
PRICE/PERFORMANCE AND VALUE  (I´ll admit this is a kind of ambiguous aspect)
 
 
This is the aspect where I can give 10/10 without hesitation. Why ? HE-400i offers tremendous price/performance ratio, for 500 dollars (euros) you get a headphone which can hold its own very respectfully against some of the best headphones in the world and is even pretty competitive (with them) in some sound aspects. Despite being a bit worse in overall sound quality vs HE-560, LCD-2, Oppo PM1, HE-6, LCD-X or HD 800 the difference is actually much tighter than the price tag would suggest.  While spending 500 dollars/euros for a headphone is not a „bargain“,  it is in fact a very generous price for this audio product –  taking into account its impressive sound quality and also prestigious looking leather box, which comes in a package with HE-400i.
But the overall value of HE-400i goes further than just to „respectful sound quality for 500 bucks and a nice box“. Thanks to its non-fatiguing yet at the same time engaging sound and impressive wearing comfort is the Hifiman HE-400i literally a perfect headphone for longer listening sessions. HE-400i, as a fairly efficient headphone, can also be used with decent portable players, which allows you to get (back) into the world of high quality sound within a few seconds...  These valuable assets were also taken into account when giving my overall score for this product.
 
 
SUMMARY
 
 
 By counting all 10 grades from all 10 sound aspects I got the number  88.5/ 100. That´s a pretty high score, but to me it seems subjectively fair. Yes, maybe HE-400i did not quite excel in any of the aforementioned sound aspects (In none of the ten analysed sound aspects it got 10/10 ! ) but I felt these headphones offered very solid performance in all examined areas. Maybe small compromises were here and there, but the overall versatility and consistency in sound quality was apparent in all sound aspects and for all examined genres (rock, pop, classical, metal, blues, jazz, new age and electronic). Although I have compared HE-400i with higher end headphones only for a relatively short amount of time, I feel confident in saying that HE-400i is very very close to the top level headphones (grade 90 and above). Well, for me HE-400i is a kind of „entrance gate“ to high end sound. And while the asking price is not cheap - around 500 dollars/euros -  it´s easy to recommend these headphones to all audiophiles on a „lower“ budget, because the overall price/performance factor is even better than 8.85/10...
 
 
Bottom line
 
 
If it was only for the sound quality alone I would give HE-400i four and a half star. But taken into account also the price/performance ratio, the level of comfort and fairly good efficiency (for a planar headphone) I decided to give this audio product five stars.
 
 
 4,5/5 stars  (or to be more precise 88.5/100)  - for the sound quality             5/5 stars - overall rating for the audio product
 
 
POST SCRIPTUM
 
 
After burn in (150 hours and more) it seemed to me that the sound was generally smoother and the bass was a bit more impactful/extended. Otherwise I have not felt, there has been significant changes. Of course, YMMV...
 
The sound potential of HE-400i can be probably further enhanced by modification (http://www.head-fi.org/t/698974/hifiman-he-400i-impressions-and-discussion/3510 or by using a balanced cable ( http://www.head-direct.com/Products/?act=detail&id=211).   After the modification has been done, some users reported improvements such as: better soundstage, better imaging, bass or treble extension... However, I don´t know how much of an overall improvement can be achieved by modification. Nevertheless, I am not interested in any modification of HE-400i because I am already satisfied with the sound quality and the sound signature from the stock model. Besides of that I do not feel technically competent „for the job“.  On the other side in the future I would like to buy a balanced cable and Oppo HA-1 – a highly capable headphone amplifier /DAC offering  XLR connectors, enabling to use HE-400i in a balanced mode. I guess this is a way for me to go...
 
 
That´s it. Thank you for reading ! Kudos to your stamina   Greetings from Slovakia, Martin

Disclaimer: I am using it out of my PC, I don't have an amp with it yet and I will be modding these fairly soon, which should improve the sound, so I will update this review when I get there.
 
Initial impressions
Before break-in, they had much less bass, other sound aspects didn't change very much though. The build quality is nothing special, it is alright I guess, has some metal and some plastic in it, not too bad, but they are not for throwing around, and I am concerned about the longevity of the moving parts such as the adjustments in the headband. The cable, in my opinion is very bad, but not from an audio standpoint, don't worry about that, no microphonics, it does what it's ought to, but the sleeving is poor quality, and I really don't like the right angled 3.5mm jack. The headphone is very comfortable though. I did have some initial fatigue because of it pushing my glasses, but I think it bent it so now it is flush with my head, and also, it has some very minor pressure, which doesn't bother me having come from terrible gaming headsets and it can be loosened if it hurts you. So no problems with comfort personally.
 
Sound
 
Bass: These headphones are considered warm, and I have to agree with that, I think these have very nice extension, and power, but when very low, it loses some control and a bit of impact in my opinion, also, it can get a bit faded or hazy, still very good though, when getting closer to the mids, it gets really sweet, with a lot of power and kick, and is very present. Almost perfect. If only it had a tiny bit faster attack.
 
Mids: I'm in trouble with describing mids, as I don't have a lot of experience in this department, but I can say that it is, not overly, but realistic, a little bit laid back, which is not for my liking, and higher up it loses some presence, as if there were layers of sound, and mids would get back, a layer further from you. What I really like though, and this is not necessarily only the mids, but I would say mostly, is the timbre! These headphones make percussion and anything that is made of wood sound so real, vibrant. Bass is good when you can feel it, not hear it, but you don't really think that mids could be felt too, until you listen to this headphone, which just reproduces them just the way they are supposed to sound. Vibrant, woody, hollow, you can almost see the guy hitting given instrument, or blowing down it. 
 
Treble: In my opinion, this might be the only department that these cans are lacking for me, it is certainly good, and nice sounding, even the extension is ok, but the way it sounds is just not for me. It is not quite as sharp, attack-y, fast, and most importantly up-front, engaging, and forward as I would like it to be. Still gets very close to it though! 
 
Other attributes: The soundstage is fairly large, nothing crazy here, but it is involving, and does everything it should to make you forget about it, and satisfy you. 
 
Update: (20.03.2017) First impressions after removing the mesh. Soundstage opened up, imaging became more detailed, treble raised, the sound got more of a crunchy or crispy quality, and last but not least, probably because of these improvements, micro-details emerged. Also, a darkness, or veiled quality is relieved.