By aspect — in detail
Tonality
Contested · 12 srcThe headline disagreement. The bench sits close to target, and most reviewers call it neutral or 'bright-neutral.' A minority hear it as outright bright (wanting a warm, powerful source), and a few hear a warm lean instead — a split that tracks, in large part, how hard and how warm the source drives it.
Measured
On the bench the HE400se tracks close to the Harman target (ASR: response 'complies with our target well … usable without equalization'), with the trademark HiFiMan dip around 1–2 kHz, mostly-linear bass and mids, and a mid-treble peak near 7 kHz plus narrow resonances higher up. Sensitivity is below average (~91 dB/mW) despite low impedance.
⚠ vs. listeners — The graph is broadly neutral; 'bright' versus 'warm' versus 'neutral' is largely the same near-target tilt heard through different amps, sources and ears. Reviewers who under-power it or pair a lean source hear 'bright/thin' (Audiophile-Heaven frames the brightness as a symptom of under-driving it); those on a warm, powerful desktop chain hear 'fuller/warmer' (Headphoneer). The disagreement tracks the pairing at least as much as the headphone.
Where it splits
Neutral / bright-neutral — balanced and close to target, usable without EQ.71%
“I would describe the HE400SE’s tonal balance as one that leans towards what I personally consider to be “neutral”-sounding, with linear bass and mid responses, as well as a mostly-even treble range.”
Chrono (headphones.com)
Bright — treble-forward; needs a warm, powerful source to sound right.14%
“While sundara was delightfully bright, He400SE is quite bright and needs a warm and smooth source to sound alright.”
Audiophile-Heaven
Warm-leaning — fuller and warmer, especially well-driven.15%
“It is warmer sounding with more body in the mids, but lacks the huge soundstage and great imaging of the X3.”
Headphoneer
The most-argued sonic axis. Sources agree there's a peak around 7 kHz (with resonances higher up); they split on how it lands. One camp hears it as sharp, tizzy or gritty; the other hears the top end as smooth, detailed and non-fatiguing — even best-in-class. The divide tracks the recording, treble sensitivity and a little EQ.
Measured
Sources locate a peak around 7 kHz (Fc-Construct, Chrono, TechPowerUp) with additional narrow resonances ~8–10 kHz (DIY-Audio-Heaven), over otherwise good extension and air above 10 kHz; distortion is very low. It responds cleanly to a few dB of cut around 7 kHz.
⚠ vs. listeners — Same peak, opposite verdicts: it sits just above the 5–7 kHz sibilance region, so on bright recordings or treble-sensitive ears it reads sharp/tizzy, while others hear it as detailed and non-fatiguing — and a small EQ cut resolves it for both. Home Studio Basics notes the old HiFiMan 'hiss/bite/essiness' is 'gone' on this model.
Where it splits
A ~7 kHz peak that reads sharp / tizzy / gritty on some tracks.36%
“Treble is smooth but has a sharp edge on it. This, however, is easily solved with some EQ or filtering.”
DIY-Audio-Heaven
Smooth, detailed and non-fatiguing — remarkably well-tuned for the class.64%
“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.”
TechPowerUp
Everyone agrees on the facts — the sub-bass rolls off, and what's there is tight, fast and low-distortion but short on slam — and that it EQs cleanly. The split is whether that reads as lean and unsatisfying or as clean and plenty for the price (especially once properly driven).
Measured
Extended but level-light: sub-bass rolls off (Fc-Construct locates it ~40 Hz; Chrono notes no shelf under 120 Hz), so it's tight, fast and low-distortion but short on slam. It takes bass EQ cleanly, though a boost needs a beefier amp. Owners of the current 'Stealth' version report punchier, tighter bass than the older non-stealth unit.
Where it splits
Lean / sub-bass-light — clean and fast but short on slam; wants EQ.74%
“In my books, sub-bass is where the HE400se is the weakest even relative to many open-back dynamic driver headphones”
TechPowerUp
Present, fast and satisfying — controlled and plenty for most, especially well-driven.26%
“Some will complain that the bass doesn’t slam hard enough, and while I understand the sentiment, I don’t entirely agree.”
Home Studio Basics
Broadly a strength: clean, linear mids with a natural timbre and good clarity. The recurring caveat is the HiFiMan 1–2 kHz dip and late-rising pinna gain, which can make the upper mids read a touch forward/dry and push some female vocals back (or, on a few tracks, toward nasal).
“Unsurprisingly, I have come to adore the mids on these. I found myself appreciating nuances that previously went unnoticed”
TechPowerUp
“As such, the upper mids can come off as slightly dry.”
Fc-Construct (headphones.com)
Measured
The HiFiMan 1–2 kHz dip (~3 dB, Chrono) with pinna gain that only rises after 2 kHz (Fc-Construct, TechPowerUp): mids are clean and linear but the upper mids can read forward/dry, and on some tracks push female vocals toward recessed or nasal (Acho, TechPowerUp).
Soundstage
Moderate · 8 srcCalled open and spacious for the price without being holographic. Most put width roughly on par with the HD 560S and ahead of the HD 600/650 for a sense of distance, with modest depth; a couple of reviewers expected more from big planar cups, and a few find it a bit intimate for gaming.
“The HE400SE actually has one of the more spacious and open-sounding presentations in its price bracket.”
Chrono (headphones.com)
“I still found the 400se a bit too claustrophobic for gaming.”
Home Studio Basics
Measured
Reviewers put width roughly on par with the HD 560S and ahead of the HD 600/650 for a sense of distance (Chrono), with modest depth — open and spacious for the price rather than holographic.
Two things at once: layering and instrument separation are a planar strength, but positional imaging is front-focused with a weak center image — which is why several reviewers steer competitive gamers elsewhere.
“The HE400se's imaging does a good job in allowing instruments to layer three dimensionally on top of each other without fighting on the same 2D plane.”
Fc-Construct (headphones.com)
“Where I do find that the HE400SE performs somewhat poorly is in its imaging, as it lacks the degree of precision that you get with HD560S or DT990 Pro”
Chrono (headphones.com)
Measured
Layering and separation are a planar strength, but positional imaging is front-focused with a weak center image (Chrono, TechPowerUp) — good for casual listening, weak for competitive shooters.
Widely called a 'new baseline' for the class — genuinely good detail retrieval and clarity for the money, close to the HD 560S. The honest caveat: resolution isn't outstanding in absolute terms, and budget, non-hand-matched drivers can show minor channel imbalance.
“The technical performance of the HE400se is what I'd consider the new baseline for so-called "audiophile" headphones.”
Fc-Construct (headphones.com)
“At the same time, I did find myself wanting more resolution from the drivers.”
TechPowerUp
Measured
Very low distortion (ASR, DIY-Audio-Heaven call it 'exemplary') and a class-baseline level of resolution; channel matching is praised by some (DIY-Audio-Heaven) but TechPowerUp caught minor imbalance — expected of budget, non-hand-matched drivers.
Classic planar speed — quick, clean transients and good attack/decay are agreed. The debated part is macro-slam and low-end impact, which several find lacking out of the box and which improves markedly with more power.
“attack, sustain, decay, and release are all markedly better with a planar, and this has a lot to do with their driver structure.”
Home Studio Basics
“it really feels lacking when it comes to delivering a satisfying, defined impact in the low-end.”
Chrono (headphones.com)
Measured
Fast planar transients with light macro-slam, tied to the sub-bass roll-off and the need for power; it scales up noticeably on a strong amp (Headphoneer drove it off 100 W speaker taps for 'way above its price-point' results).
Mostly positive: light for a planar (~385–390 g) with large, comfortable pads, and comfort reviewers rate among the best HiFiMan has done. The caveats are real, though — headband soreness after an hour or two, no horizontal cup swivel, open-back heat, and small pad openings for larger ears.
“comfort ends up being the best it’s ever been concerning HIFIMAN products.”
Home Studio Basics
“I do get the common problem of headband soreness after an hour or two.”
Fc-Construct (headphones.com)
Measured
~385–390 g with a one-piece metal yoke and large pads; clamp reads medium (DIY-Audio-Heaven ~3 N) to slightly-low (TechPowerUp), the cups don't swivel horizontally, and the open-back cups run warm. Owner ratings split roughly 2:1 positive on comfort and fit.
Two true things at once. The frame is widely called sturdy-enough for the price — metal yokes, simple and functional. But the stock cable is nearly universally panned, the plastic cups and pad glue look cheap, and HiFiMan's quality-control reputation shadows it — even as many owners report years of trouble-free use.
Measured
Metal yokes on plastic cups, with a stock cable widely panned as stiff and microphonic (ASR calls it a 'thin, horribly coiled wire'; Fc-Construct, Chrono and Acho agree), pad glue/flattening (Home Studio Basics), and HiFiMan's driver-failure/channel-imbalance reputation. Amazon owner reviews run net-negative on reliability (14:19) and cable (13:14) even as sound and value run strongly positive, and a self-selected Reddit poll put brand-wide issue reports near a quarter — countered by many trouble-free owners and HiFiMan's cheap, responsive warranty/refurb.
Where it splits
Sturdy and functional for the price — metal yokes, simple, does the job.34%
“The 400se actually feels sturdy and functions flawlessly, as the design is simplistic and utilitarian.”
Home Studio Basics
Cheap cups, a dreadful stock cable, and HiFiMan's QC shadow.66%
“What's not acceptable is this cable. It's horrendously stiff with an awful case of cable noise. It's like barbed wire without the barbs.”
Fc-Construct (headphones.com)
Isolation
Strong consensus · 4 srcOpen-back by design: essentially no passive isolation, and it leaks freely both ways. Expected for the type, not a flaw — but it rules out commutes, offices and shared rooms.
“Sound isolation isn't much of a thing on larger planar magnetic headphones, and the HE400se is no exception.”
TechPowerUp
“If pushed to maximum volume, they practically become two speakers.”
MobileAudiophile
Measured
Open-back — no meaningful isolation and free leakage both ways, by design (TechPowerUp, MobileAudiophile, Audiophile-Heaven).
Value
Strong consensus · 11 srcThe near-universal verdict: the cheapest real way into planar sound and one of the best-value open-backs going. The only asterisk is the total cost — you should budget for a proper amp and, usually, a replacement cable on top of the ~$109 sticker.
“That it comes at such a low cost is a huge bonus, making the HE400SE one of my best picks for a bargain headphone.”
Audio Science Review (amirm)
“I believe the 400se is still the best mid-fi value for the quintessential planar sound at an insane price point.”
Home Studio Basics
Measured
~$109 now (launched $149.99); near-universally recommended as the budget planar to beat, with the standing caveat that you must budget for a real amp and, usually, a replacement cable.
