Comparison: Hifiman He 400i and Sennheiser HD 660S2
Scooped mids are for the mix 🎚️🎛️🎚️🎤💽, not for the headphones 🎧
[Side view of Hifiman He 400i headphones]
A friend recently lent me his Hifiman He 400i headphones. He said the ear cups and cup mounts “kept falling apart,” so he replaced the ear cups with aftermarket ones, and he is using 3-D printed cup mounts.
I start out with the Cayin N7 DAP as my source, playing back files that are stored on the device (not streaming). Initially, the Hifiman He400i lack soundstage depth to the point of lacking liveness, and everything seems crammed into the center. The high end is admirable at this price point, and the sub-bass is powerful and prominent. I compare it with my Sennheiser HD660S2’s, which are at about the same price point, though it is hard to pin down the He 400i price point in 2023. (I review the Sennheiser HD660S2’s here https://open.substack.com/pub/hanscox/p/review-sennheiser-hd660s2-open-back.) The Hifimans are planar magnetic while the Senns are dynamic. The Senns have a palpable sense of space, and they are not slouching in their high end. The HD660S2’s are probably most known for having more sub-bass than other models in the 600 series. And the Hifimans have good sub-bass too, perhaps even more of it than the HD660S2’s.
Listening to track one on the Grant Green album Funk in France, “I Don’t Want Nobody to Give Me Nothing,” the tonal balance is excellent. When I switch to the Sennheiser HD660S2’s, I notice less highs and lows than the He 400i’s give, but there is a palpable soundstage, a sense of space that seems to surround me. This album, however, does not have wide soundstaging with either pair of headphones, nor with the Skullcandy Hesh ANC’s, which I tried for comparison. The Brad Mehldau Trio’s album, Art of the Trio Vol. 4: Back at the Vanguard, has a remarkable soundstage—very wide, especially with open-back headphones. Here, the Hifiman He 400i’s get to show off the wide soundstage typical of good open-back headphones. If I could have the combination of tonal balance with exquisite highs, of the He 400i’s, and the deeper, bigger, wider soundstage of the Sennheiser HD660S2’s, I think that would be the best of both worlds. I like a slightly scooped-middle sound, which the Hifimans have. I like a big soundstage.
[View showing inside of Hifiman He 400i aftermarket ear cup, with fluffy lining]
These Hifimans are great for jazz, with their sizzling cymbals standing out in the mix, and the deep acoustic bass standing out about as much. The Sennheisers are great for having more of a sense of liveness, especially important for live jazz recordings such as these Grant Green and Brad Mehldau Trio albums. They have a flatter response, with much more midrange sound than the Hifimans.
Both headphones have about the same weight, and both are light. The Sennheisers have a firmer clasping force, but the Hifimans stay in place during head movements (unlike the heavy and luscious Sendy Peacock planar magnetic headphones I review here https://open.substack.com/pub/hanscox/p/review-sendys-peacocksopen-back-over). It may be unfair to compare the Hifiman He 400i’s to the higher price-point Sendy Peacocks, but I did, briefly, and there is a larger soundstage with the Peacocks. The soundstage is larger—wider and deeper—with the dynamic open-back Focal Clear Mg’s, and this is another unfair comparison, yet comparison with higher price-point headphones allows the possibility of the lower price-point headphones to surprise the listener with the quality of their sound.
Switching to the Astell & Kern A&futura SE180 DAP, with the SEM4 DAC module with optional upsampling/remastering to DSD 64, just like the Cayin N7 was doing, and playing tracks stored on the device, I try out the Hifiman He 400i’s with Blacknote’s title track on 43rd & Degnan (the cross street where the World Stage recording label was located—run by the great jazz drummer Billy Higgins). I’ve become used to the tonal balance of the Hifimans. The cymbals stand out well, especially since the drummer on this album is excellent. Initially, the low end seems light. Even low, open strings on the acoustic bass seem too light. I know these headphones can pump out strong, deep bass, so it is just the recording itself—that or the DAP.
The scooped-mid tonal profile of the Hifimans allows the trumpet and soprano sax to play their repeated motifs without offending the ear. Headphones with more midrange tend to have me turning the music down, on this track, which has a lot of repetition of loud, staccato figures on sax and trumpet. There is the sense of being just outside a wide doorway, with the band playing in another room, though occasionally some instruments reach out from the far edge of the shallow soundstage. This recording has a deeper soundstage to it than the Mehldau Trio at the Vanguard—I find Village Vanguard recordings to have very wide, though shallow, soundstages. In comparison to the Hifimans, the Sennheisers produce a more balanced tonal palette, with more mid-bass at the start of the track, which seemed very light through the Hifimans. The midrange is immediately noticeable as more forward, though not standing out more than would sound good. I feel more as if I am in the room with the band. And the room feels large, with a high ceiling.
Changing to Beethoven’s Symphony #5 in C minor, the scooped-mid tonal profile is at odds with the high midrange content of most classical, orchestral music. The double basses stand out, and the deepness of their sound is impossible to miss. The brass has a lot of brassy buzz, given the extended high end response of the He 400i’s. The woodwinds are light and airy. The upper strings—violins, violas, cellos—typically prominent are the least prominent in the Hifimans. They sound thin and weak, with little detail being resolved.
Swapping out the Hifimans for the Sennheisers, I find the first movement sounds more powerful given the stronger midrange response. The strings sound as a unit, a balance of low, mid, and high tones. The sub-bass of the double basses can be heard, but it is not synthetic sounding, because of the mid-bass response being stronger with the Sennheisers. The brass are brassy without overly emphasized treble range, and they have more mid-range power. In summary, the Hifimans are not my choice of headphones for orchestral music.
One of my go-to tracks for listening to new headphones is Bibio’s “Out Goes the Light,” from their BIB10 album. I am expecting the Hifimans to show themselves well in this one. The Sennheisers are doing well, reproducing the sub-bass in whatever is used for a kick-drum sound. Mid-bass sounds good, with the bassline not booming over the drum but set a bit above it. The guitar—clean, chorused and twangy—is sensual and delicious.
The Hifimans do a good job with the instruments that have lots of bass or treble, but the scooped-mid profile makes the vocals, a featured attraction of this track, fall flat and sag. The mids of the guitar, so important for getting its twang to come out, just aren’t strong enough, on the first guitar heard on this track, to give the twang its oomph it deserves. The high-mids are missing, especially, and the guitars—like Beethoven’s strings (so to speak)—sound weak and thin. This is not what I was hoping for.
[Front view of Hifiman He 400i headphones]
Now, I expect this to be a cinch: Metallica’s “Battery,” from Master of Puppets, through the Hifimans. Metallica had heavily scooped mids at that point, and the Hifimans emphasize that. Cliff Burton’s typically low-toned bass is easily heard. James Hetfield’s vocals are balanced well with the rest of the ensemble, not too forward and not in the background. Kirk Hammett’s wah-wah guitar solos are beautiful. These are Metallica-tuned death-metal headphones. Now, one more track on this album, since this is so much fun now. “Leper Messiah” has long been one of my favorites. The use of dissonant dyads that quickly resolve to consonance is part of the reason for my attraction to it. Hammett’s musical ideas are among the best Metallica solos and lead accompaniments, I think. And Lars uses the kick drum to good effect. The solos are wonders to behold, and still I have no complaints about the Hifimans for this album.
As a different heavy-metal test for the Hifimans, I choose some midrange-heavy death metal, “Hell Awaits” from Slayer’s live album Decade of Aggression, streamed at CD quality via Qobuz. The guitars in Slayer, here, have more much more midrange in their tone, than those on Metallica’s Master of Puppets. Almost immediately I am disappointed by the scooped-mid tonal profile of the He 400i’s taking away much of the chainsaw-like tone of the pounding rhythm guitars, distorted almost beyond recognition as a string instrument. The saving grace is that bassist and vocal Tom Araya’s voice sounds good. I could get used to these headphones as headphones for listening to heavy metal, I guess, but frankly, I don’t see why I would. I would go for the Sennheiser HD660S2’s over the Hifiman He 400i’s. Whether this is a fair comparison may be questionable, since I’m not sure they are at the same price point, since I’ve had trouble finding reliable figures for the He 400i’s. How fair is a comparison of a pair of dynamic-driver headphones to a pair of planar magnetic headphones? I'm not sure. But they're headphones that seem similar in some superficial ways, so I figured I would give a comparison a good effort.
As a last listening test, I’m going to try some electronic music. Aphex Twin just released an EP, Blackbox Life Recorder 21f / in a room7 F760. It sounds good on the Hifimans. I tend to think of electronic music as more flexible in what tonal profiles I like to listen to it with. The He 400i’s do well with the sub-bass synths, and the cymbals sound very sizzly, like vocal sibilants. The soundstage extends nearly as widely as the Sennheisers’ does. I still like these less than I like the Sennheiser HD660S2’s because of the illusion, with the He 400i’s, that the music recording has much less mid power than it does through headphones with a flatter response.
In the end, I find I can get used to most headphones I’ve tried out. When I compare them, I find I like some better than others. And here it is, a disclaimer, for fair is fair; this comparison is really just my opinion about these headphones, however my statements may be phrased, that is, even when I speak as if I am stating “objective” facts. Our hearing, taste, and all the rest, are different for each of us.