Fit and Comfort

Seen above is the HIFIMAN HE400se on a headphone stand that is actually a set of two artificial ears complete with soft-molded human ears and a couple of different adapters acting as the top of the head. This has been mounted on a tripod, which also showcases how headphones would look on a human head, with the artificial ears spaced ~20 cm apart. As with all headphones, getting a good fit and seal is crucial, and make sure to properly use the pivot points and height adjustment on the headband and ear cups thus. This section is mostly a summary of the points expanded upon in more detail on the previous page, whereby I will again point out that the HE400se weighs 390 g but does not feel heavy on the head if properly positioned. It's not as comfortable as some heavier headphones though, and the headband with the lack of horizontal swivel is primarily to blame here. Clamping force is also slightly lower than I'd like, which could be due to this particular sample already having been broken in courtesy another reviewer before it was sent my way. If you find the clamping force too high, you can carefully bend the steel band outward by raising it all the way up to expose it below the headband and pressing outward there. Be careful when doing so lest you loosen it up too much permanently. Sound isolation isn't much of a thing on larger planar magnetic headphones, and the HE400se is no exception. As such, those around you are likely to get a second-hand listen of whatever you are listening to, and the external environment will play a big role in how much you enjoy listening with these.

Audio Performance

Audio Hardware

I won't go into detail on the workings of planar magnetic drivers, having covered it before. To summarize, it involves the use of ultra-thin diaphragms with conductive traces as the voice coil. This allows for theoretically lower inertia paired with high magnetic flux fields generated from magnets to move the diaphragm back and forth very quickly for fast transients and increased resolution while lowering distortion. HIFIMAN is not sharing any details about the diaphragm in the HE400se, which usually is code for "not as good as we have it in other, more expensive headphones." With "good," I am simply referring to the thickness of the diaphragm, nature of the voice coil (magnetic traces), and actual magnets. For the latter, we see similar stealth magnets as on the much more expensive new Arya. However, not as rounded or strong as those in the Arya, these do not seem as well-executed. HIFIMAN has the luxury of locally sourced, strong neodymium magnets to lower any resonance impact on the sound waves generated from the diaphragm. It does seem as though the stealth magnets are not all created equal.

Regardless, symmetrical magnets are on either side of the diaphragm, and these are smaller than before and curved to where standing waves do not incur diffraction, which keeps distortion low. HIFIMAN thus claims these magnets to be acoustically transparent, or at least as best as currently possible in this budget range. The drivers make for a set of headphones that are fairly typical of current-generation planar headphones in that they are relatively low on impedance at 25 Ω, but then require more power than many headphones with a below average sensitivity of 91 dB/mW. Amplifiers capable of providing ~0.5 W at 25 Ω will have enough headroom to account for transients as well, since that will output more than 100 dB already. Most portable DAC/amp units will be found wanting though, in some cases even with a balanced cable, so the HE400se is better-suited for desktop use.

Frequency Response Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature emphasizing a slightly elevated bass and smooth treble range with detailed mids and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


We now get to use our new headphones test setup, which has a set of two custom in-ear microphones for the two channels. These microphones closely adhere to the IEC711 class, but have been tweaked to be more reliable in the >10 kHz frequency range that was the issue with my previous setup, which is still very good and will continue to be used for IEMs and earphones. Two soft silicone pinnae are installed on the sides, separated by a distance matching my head, and multiple "height" adapters have been 3D-printed for further customization based on fit and head size and shape. Each set of microphones has an XLR output I separately adapted to 3.5 mm. I did power the headphones off a dedicated source, the JDS Labs Element II.

This artificial head simulator feeds into a reference USB sound card, which in turn goes to a laptop that has ARTA and REW running and the headphones connected to the laptop through the sound card and/or a separate DAC/amp if needed. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. The raw data is then compensated based on a custom curve created after having worked with Crinacle from In-Ear Fidelity to get measurements with this setup on par with a GRAS 043AG industry-standard measurement rig, so big thanks to him for that. Give him a subscription on his new YouTube channel if you like his work, the poor guy lost access to his immensely successful older channel recently.


That was the biggest update since the last headphones review, which is also why there haven't been any in the last couple of months. The other update is that I am retroactively measuring all the headphones I have here, including those previously measured and reported, while adding them on VSG.squig.link along with all the earphone measurements. Do note that since they are mixed in there, the default "VSG Target" is my preferred one for earphones, with a different pinna gain and bass boost as opposed to my preference for over-ear headphones. Scroll to the bottom and choose different targets there, as I added new ones, including two from Harman Kardon developed after years of R&D. The Harman 2018 over-ear target in particular is a reference curve many headphone makers aim for now, but I find it too bass-boosted. As such, I am opting for the Harman 2018 curve with the bass target from the Harman 2013 curve, which is what is being referred to as the "Harman Combined" target there. This idea came from a highly experienced reviewer on the Headphones.com review team, so I'll give Resolve due credit while recommending his work as well.

Having listened to quite a few different HIFIMAN products over the last few weeks, which is also a hint of what's to come, the HE400se clearly follows the company's house sound. This is especially evident with the scoop at 1 kHz, where you would otherwise expect to see pinna gain result in SPL elevation instead. There's a train of thought about having a dip at 1 kHz for vocal bleed, before a rise from 2 kHz to account for where throaty sounds are produced. I can't say if HIFIMAN subscribes to this, but it sure again looks like it here, which makes the upper mids come off artificially brighter than is actually the case. This is where I can see some people disliking the tuning, with the potential for some female vocals coming off as nasal, or even shouty. Having gone back and forth multiple times, I don't think it's overly bright myself, but keep my preferences for generally brighter and treble-emphasized music in mind.

The tuning of the HE400se is aiming to be fairly neutral, but the drivers and frequency response make it less ideal for monitoring than something flatter in the bass and mids. This being an open-back set of headphones, I was not expecting a bass shelf akin to what we saw with the closed-back Meze 99 Neo, and the driver limitations relative to more expensive headphones is indeed primarily seen in the lack of sub-bass extension. In my books, sub-bass is where the HE400se is the weakest even relative to many open-back dynamic driver headphones, whereby the planar advantages of fast decay and relatively high dynamics are not appreciated. Fans of EDM, house, and electronic music may want to look elsewhere. By comparison, the bass proper comes off fairly neutral relative to the mids, so much so that you may want to EQ this region to make bass guitars and kick drums play well. There is enough leeway with linear distortion to do so, especially considering planar drivers tend to have a linear impedance across the entire frequency range. I used Equalizer APO with Peace GUI and successfully set a bass shelf of 3–4 dB starting at ~250 Hz and below—just set the default preamp to -6 dB and call it a day.

Knowing the HIFIMAN house sound is more about detail and classical and orchestral music based on the tuning, the mids did not surprise me. By default, there's no felt transition from the bass to the lower mids. This will be the biggest change for people who have used closed-back headphones with a more bass-emphasized V-shaped tuning. Make sure to give yourself some time to get used to the HE400se if you are in that situation. Vocals and instruments will come off very differently from before, often feeling "wrong" simply because it is different. Give the brain a week or two to get used to this, and you will start appreciating the layers abounding here. It's no one-trick pony, with plenty of range to allow different instrument classes to shine. At the same time, I did find myself wanting more resolution from the drivers. This could be a result of having listened to some other excellent planar magnetic headphones recently that showcase the possibilities of the platform, but it thankfully does not get in the way of imaging, whereby I will say it is good enough not only for the likes of orchestral music, but also movies and even gaming. Indeed, combined with a relatively uniform soundstage that is about average for over-ear headphones of this size, you have a very specific imaginary field in front of you inside of which where sounds are coming from is easily identified, including footsteps in competitive shooters. Wider sounds towards your ears are hazier, though.

Unsurprisingly, I have come to adore the mids on these. I found myself appreciating nuances that previously went unnoticed, so much so that I may have to buy some CDs or FLACs to make sure local files I have are not with recording errors. Perhaps this is where the reference aspect comes back, with so much range to vocals and instruments that I found myself listening to music I generally don't even frequent. But it was time to go wild even with some Tejano music in the mix to represent my old home of Houston, Texas. Male vocals were so detailed and had just enough energy that I almost ignored that vocals are not my preference in music. This range lends itself well to the soundstage too, which more or less follows the shape of the ear cups in being taller than wider. It is extremely spacious, almost coming off as small speakers further away from your ears, with the sound-field mapped out mostly in front of you regardless. I would have liked more holography, especially after reading so many positive comments about the soundstage, but it is still one of the most open sets in that regard, just not necessarily for gaming, if you are weird like me and try it out with these. Though quite precise, Imaging is more front-focused. Sounds coming from the side are centered around maybe a 120–150° field in front of you.

The treble response had briefly been touched on already, and there are shades of brilliance. The tuning is one of the very best I have heard across all headphones, and this is generally true regardless of whether you are a proponent of the Harman target or not. It's smooth, detailed, and non-fatiguing without being bright. I even had some bassheads listen to this, and it was a convincing set for jazz and funk music, as well as pop and R&B. I wish channel matching were better though, since I had a couple of instances where some piano keys were louder on one side than the other, but such is the nature of the budget planar headphones market that you can't expect hand-matched drivers. The HE400se is tuned even better than the Arya in this region, and that set costs $1600, but is in turn tuned better than the $3500 HE1000se in the HIFIMAN lineup. So far, only the flagship Susvara does better among those I have here, but this is a real testament to the HE400se.


When I moved from the US to the UK, I got rid of a significant chunk of my personal audio collection, including a couple of beyerdynamics, Audio-Technicas, and Sennheisers. As such, and given the time that has passed since, I will refrain from comparisons to headphones I no longer have solely based on my recollection. Shown above are instead three others I do have on hand, including the Sennheiser HD 6XX, Philips Fidelio X2HR, and Sennheiser HD 598 that is the very first set of "proper" headphones I ever bought for myself. Note that the former two are like new with pads that are reflective enough of the retail experience, whereas the HD 598 has slightly worn pads, which likely lowers the bass response compared to a new unit. The HD 6XX is also typically more expensive, but the other two are on par with the HIFIMAN HE400se in pricing even today. I will say that the HE400se is the best-tuned set of the lot in my books, and a lot of this again comes down to the treble response, where the others barely come close. The Fidelio X2HR is a bassier set with warmer mids and lower detail, the HD 6XX is also warmer but significantly more damped in the treble, and the HD 598 is shouty and a touch sibilant here. When it comes to the technical performance, I will again give the edge to the HE400se even though the Sennheisers fight well, especially the HD 6XX. Build quality and comfort is where the HE400se loses out to all three, with the Sennheiser pair being lighter, and the velour pads are just dreamy in use. The Fidelio X2HR has a very nice suspension headband with matching velour pads, too. Overall, I'd still take the HE400se over all three, especially now that the HD 6XX has had a price hike and HE400se a price drop.