It goes without saying but keep in mind that I am reviewing the variant with 2.5mm connectors. I have not tried any other variants except the original one but I’ve only had it under trade show conditions 6 years ago so it’s as good as not having tried it by now.
The HE400i to my ears has a tonal balance of slightly on the warm side of neutral without a hint of bloat in the bass frequencies or sounding thin or too clinical in the upper frequencies.
The bass is not fully extended and can be perceived as slightly soft in impact relative to what you’d normally get from a good sealed headphone. I don’t want to exaggerate that though, I feel while it’s lacking in sub-bass, the rest of the bass presence is fairly flat and one that old school audiophiles will like tonality wise. It doesn’t have a bump or wide emphasis in this area.
As a result, the bass to midrange transition is quite good. You don’t feel something is not integrated or bleeding, and most of the midrange tread this fine line of either being slightly recessed or forward depending on the tracks. The upper midrange is lower in level which is a common sight when looking at frequency response but the tail-end going to the lower treble has a small peak. It wiggles unevenly before showing another peak again at 9-10Khz.
It results in some shrillness in how electric guitar is portrayed at times, while the cymbals can come a little across harsh and sibilant. Personally, it’s quite bearable but I can easily see a handful of folks being annoyed with this. Depending on the type of music that you’re listening to, this can add some liveliness to the mix or make the experience more fatiguing.
The stage has a good sense of width but not as much height which is typical of open headphones in this price range. If you’re coming from a closed headphone, you would appreciate the openness of this one.
Imaging is quite average for an open headphone and while separation is respectable, I find the peaks in the treble contributing to slight grunge that overlays to the music especially for fast rock genres.
For a headphone that has a neutral tonality, I find its transient response to be not as fast as I was expecting quite possibly due to the soft dynamics and treble peaks. It’s not slow sounding by any means but I find it to be bested easily by Beyerdynamic DT880 and from memory, the Grado SR225i.
Finally, the HE400i plays loud enough from portable devices and crappy audio outs but amplification makes good improvements. Using my Schiit Magni 3, I find that the treble is less harsh and the overall presentation is less sucked out. The Schiit products, in general, are known for a somewhat flat presentation so I imagine the soundstage will improve with other amplifiers.
At its original price point of $449, I would consider the HE400i to be overpriced because there are better sounding headphones at a similar or even lower price range. To name a few, the Sennheiser HD598 – 650 family, the Beyerdynamic DT880 and DT1990, heck even its own Sundara can get you a better value than the 400i. If you want to fully go Hifiman’s route, the HE4xx and the 2020 version of HE400i would be worth a look as well.
If you can get it for less than $250 though, then the HE400i begins to look like a solid option. Personally, I still prefer the Sennheisers and even the Sundara with the latter being a newer headphone with an updated driver technology.
The HE400i was a good mid-fi headphone when it was released and maybe it still is, but other options that I mentioned simply ticks more boxes at a similar price point. Maybe it’s one of the reasons why the HE400i never came close again to its original MSRP.