The HiFiMan HE-400i are great critical listening headphones that are not really suitable for any other use case. They're comfortable and deliver an excellent sounding audio reproduction. However, they can sound a bit sharp on already bright tracks, and they do not have as much bass as the Edition X. They also have fairly weak hinges that are not very durable, unlike the HiFiMan Sundara, and may be a deal breaker for most critical listeners.
The HiFiMan HE-400i are decently well-built reference headphones. They have a lightweight, metallic frame that makes the headband feel sturdy. They're also comfortable to wear for long periods of time. Unfortunately, their build quality has a few flaws, especially at the hinges, where they are prone to breaking under moderate physical stress. Also, they are big, bulky critical listening headphones, not meant to be used outdoors or while doing any kind of physical activity.
The large and open ear cups of have a metallic finish and a slight blue tint that's eye-catching. That coupled with the soft suede padding and the old school leather headband give them a retro, yet premium appeal that will work for some. They do not look as premium as the Sundara and they're a bit too bulky to wear out in public, but they're not designed for outdoors so it shouldn't be too much of an issue.
The HiFiMan HE-400i are comfortable, well-padded headphones. They're a bit tight on the head, but the suede-like material used for the padding is soft and pleasant on the skin. The ear cups are not as large as the Edition X, and the padding touches the tips of some listeners'ears. However, this smaller format might be more comfortable for some than the oversized ear cups of the more premium model.
These headphones do not have any controls.
The HiFiMan HE-400i, like the rest of the planar magnetic HifiMan headphones, are not very breathable. They have an open back design which usually does not get as hot as closed back over-ears. Unfortunately, since they are planar magnetic headphones, the larger drivers obstruct a good amount of airflow, so they will make your ears fairly warm after a couple of hours of continuous listening. You will have to take breaks if you have long continuous listening sessions when compared to some other over-ears like the Sennheiser HD 700.
The HiFiMan HE-400i are big and not portable. They're a bit too cumbersome to comfortably carry on your person and do not fold into a more compact format. The ear cups lay flat but are bigger than average over-ear models, which doesn't save much space. On the upside, they are a little smaller than the Edition X, but you will still need a backpack or a large bag to transport these headphones. Also, they don't come with a protective case or pouch.
The HiFiMan HE-400i have a good build quality. They make use of premium materials, which results in a sturdy design that can handle a fair amount of physical stress. The ear cups are not as well-built as the Edition X's ear cups. However, the plastic joints connecting the frame to the ear cups is thicker and sturdier, which makes these headphones slightly more durable.
Update 12/04/2018: Multiple users have experienced a build quality defect, resulting in broken hinges/yokes under mild stress. We have therefore adjusted our build quality score to reflect this manufacturing issue.
These are not sports headphones. The large over-ear cups will sway and quickly slip off your ears if used during exercise or while running. They're a bit more stable than the Edition X and will maintain their position during casual or critical listening sessions.
The HiFiMan HE-400i is a very good sounding pair of open-back over-ear headphones. They have a consistent, punchy, and well-balanced bass, a nearly flawless mid-range, and a very good treble. They also have exceptional imaging, and a soundstage that outperforms most of the headphones we have measured so far. Overall they have a well-balanced and versatile sound and would be a great choice for a wide range of genres, especially vocal-centric music. However, because of their lack of sub-bass and slightly sharp treble, they may not be ideal for the fans of bass-heavy genres. Their upgrade, the Hifiman Sundara, are slightly less bright sounding and produce less distortion.
The bass of the HE-400i is very good. The LFE (low-frequency extension) of 54Hz is decent, but not great. Also, low-bass which is responsible for the thump and rumble common to bass-heavy music is lacking by more than 5dB. So their sub-bass may not be heavy enough for the fans of heavy bass. Mid-bass, responsible for the body of bass guitars and the punch of kick drums, is also lacking by about 1dB, but this effect will be very subtle. High-bass, responsible for warmth is quite flat and over our neutral target by just 1dB.
The mid-range is great. The response is flat throughout the range, which indicates a well-balanced reproduction of vocals and lead instruments. But low-mid and mid-mid are above our target by about 2dB. This thickens the body of vocals and lead instruments a bit, however, it won't be noticeable to most people. High-bass is within 0.6dB of our neutral target, which is great.
The treble performance is very good. Low-treble is relatively even and flat. It is overemphasized by just 1.2dB, which won't be very noticeable. However, the +5dB bump in the sibilance range (6KHz-10KHz) makes the S and T sounds, mostly heard on vocals and cymbals, a bit bright and piercing, especially on overly bright tracks. The newer HiFiMan Sundara have a slightly better balanced sibilance range.
The HiFiMan HE-400i have a great frequency response consistency. The maximum amount of deviation across our five human subjects is less than 3dB at 20Hz, but the deviation happens across a very narrow range and the rest of the bass region is exceptionally consistent. The treble delivery is also very consistent across multiple re-seat, with the maximum deviation below 10KHz being less than 2dB.
The imaging performance is great. Weighted group delay is at 0.15, which is very good. The GD graph also shows that the entire group delay response is below the audibility threshold. This ensures a tight bass and a transparent treble reproduction. Additionally, the L/R drivers of our test unit were very well-matched in frequency, amplitude, and phase response, ensuring accurate placement and localization of objects (voices, instruments, and video game effects) in the stereo image.
The soundstage performance of the HE-400i is good. The PRTF graph shows a good amount of accuracy, and a decent amount of pinna interaction/activation. However, the notch around the 10KHz region is not very accurate or deep, which suggests a soundstage that is relatively natural and large but located inside the listener's head. Also, because of their very open enclosure, their soundstage will be perceived to be more open than that of closed-back headphones.
The HiFiMan HE-400i have a good harmonic distortion performance. The amount of THD produced in the bass range is within very good limits, and it doesn't rise dramatically under heavier loads either. However, the mid and treble ranges show elevated levels of THD which could make the sound of these regions a bit impure and harsh. Their upgrade, the HifiMan Sundara, have an improved THD performance but this won't be audible to most people.
The open-back design of HiFiMan HE-400i is purposely meant to leak and poorly isolate listeners. This improves the sound quality by creating a wide and immersive soundstage but this also means, the headphones cannot be used outside effectively. They will most likely distract anyone around you with their leakage level and they will be practically unusable in loud environments.
The HiFiMan HE-400i have a poor isolation. The architecture of these headphones is completely open, and block very little. In the bass range, where the rumble of airplane and bus engines sits, they don't achieve any isolation. In the mid-range, which is important for blocking out speech, they don't isolate at all either. In the treble range, occupied by sharp sounds like S and Ts, they achieve about 5dB of isolation, which is barely noticeable.
The HiFiMan HE-400i have a poor leakage performance. These are the one of the loudest and leakiest headphones we have measured so far. Not only the level of the leakage is extremely high, the profile is extremely broad too. Most headphones either level off at higher frequencies, or roll-off, but similar to the Edition X and Sundara, the HE-400i keeps getting louder as the frequency rises. The significant portion of their leakage is between 300Hz and 20KHz. In terms of loudness, with the music at 100dB SPL, the leakage at 1 foot away averages at 67dB SPL and peaks at 86dB SPL, which is a lot louder than the noise floor of an average office.
These headphones do not have a microphone so the recording quality has not been tested.
The HE400i do not have a microphone so the noise handling has not been tested.
The HiFiMan 400i are passive critical listening headphones with no battery or app support.
These headphones do not have any active components and do not require a battery.
These headphones do not come with an app or software for added customization options.
The HiFiMan HE-400i have a simple 1/8"TRS audio cable with no in-line remote. They will only provide audio when connected to your console or PC and have practically no latency since they are wired. However, this also means that they will not have the range and convenience of wireless headsets when gaming.
These headphones are wired and do not have a Bluetooth connection. If you want a good-sounding wireless headset, then consider the Bose QuietComfort 35 II.
The HiFiMan HE-400i, like the Sundara, have a simple 1/8TRS audio cable with no in-line remote/microphone. They will only provide audio when connected to your PS4, Xbox One or PC.
The HiFiMan HE 400i do not have a dock. If you need a headset with a dock that also has a wired connection for gaming or watching movies, then consider the SteelSeries Arctis 7.
These headphones do not have a wireless range since they only connect via a regular audio cable with an in-line remote.
The wired connection of these headphones has negligible latency which is suitable for gaming and home-theater use. Unfortunately, they will not have the range and convenience of wireless headsets
The Hifiman HE-400i are great-sounding headphones with a comfortable fit and a balanced audio reproduction. They're a good choice for critical listening but will not be as good for other use cases. Unfortunately, their build quality, though premium looking is a bit fragile and weak at the hinges. This may be a deal breaker for some, especially since similarly designed models, like the ones compared below, have an equally as good sound but a better build quality.
The Sennheiser HD 650 are slightly worse for critical listening than the HiFiMan HE-400i. The Sennheiser have a slightly more durable build quality, and they do not make your ears as hot since their dynamic drivers do not obstruct airflow like the planar magnetic ones of the Hifiman. Also, the Sennheiser have an iconic sound profile which some may prefer over that of the HE-400i but have a much smaller soundstage. The Hifiman, in this case, have a more immersive sound quality. They also have a better bass delivery and more comfortable design that you can wear for longer. The fragile build of the HE-400i makes them hard to recommend, but overall, they are better sounding and more comfortable than the Sennheisers.
The Hifiman Sundara are a better built and better sounding critical listening headphone than the Hifiman HE-400i. The Sundara have much better build quality than that of the HE-400i which makes them a bit more durable although they are still prone to a few defects due to the mediocre overall quality control from Hifiman. The HE-400i, on the other hand, are a bit more comfortable to wear since the ear cups swivel to better adjust to the contours of your head, which isn't the case with the Sundaras. On the upside, the Sundara are a definite upgrade to the HE-400i and would be the better headphone for critical listening.
The Beyerdynamic DT 770 are a slightly worse sounding critical listening headphone than the Hifiman He-400i mostly due to their closed back design and weaker soundstage. On the upside, they have a much more durable design, and since they have closed back ear cups, you can use them outdoors which makes them a much better mixed-usage option than the HiFiMan. They also have a better bass range which some may prefer. The DT 770 are a better headphone overall compared to the HE 400i. However, if you only care about sound, the more spacious soundstage of the HE-400 may make them the better alternative for you.
The AKG K 712 Pro have a similar performance for critical listening as the HE-400i but they're comfortable. They also come with more accessories and their headband design despite having more moving parts is a bit more durable than the Hifiman's. On the upside, the HifiMan HE-400i are still fairly comfortable headphones and their design feels a bit more premium. They also have planar magnetic drivers that create a more spacious soundstage but it also makes them a bit warmer to wear for long listening sessions. Soundwise, the HE-400i have the slight edge but if you want the more comfortable headset, get the AKGs instead.