By aspect — in detail
Comfort
Strong consensus · 6 srcThe headline strength and the most consistent point of praise. At about 250 g with very low clamp and soft velour pads, it's repeatedly called one of the most comfortable headphones its owners have worn — an all-day, forget-it's-on fit. The only quibbles are a lightly padded headband on some heads and ears occasionally brushing the pad's back edge.
“For casual listening at home, it's difficult to beat the comfort of the Sennheiser HD 599 for long sessions.”
Jasper Lastoria, SoundGuys
“This is without a doubt the most comfortable headphone I’ve ever used. Nothing even comes close to it.”
Thememefactory7 (r/headphones)
Measured
~250 g; medium/low clamping force with soft, replaceable velour pads and a soft headband (DIY-Audio-Heaven). SoundGuys scores comfort 8.3/10, the highest of its category scores.
Warm — that's the identity, and nearly everyone agrees on it. A rolled-off sub-bass, a lifted mid/upper-bass and gently warmed mids give a relaxed, 'warmish neutral' voice that's easy to listen to and never harsh. Where descriptions diverge is degree and framing: most call it warm and smooth, some call it just a touch too warm, and a few frame the mid-bass-plus-treble shape as a mild 'V.' It takes EQ well up top but not on the deep bass.
“The overall tonal balance is a ‘warmish’ type of ‘neutral’.”
Solderdude, DIY-Audio-Heaven
“this headphone is genuinely the warmest open back headphone I’ve ever heard.”
Thememefactory7 (r/headphones)
Measured
FR shows sub-bass rolling off from ~40 Hz, a ~5 dB mid-bass lift, and a response sloping gently downward from 200 Hz to 2 kHz (warm mids), then fairly flat 1–15 kHz (DIY-Audio-Heaven).
The most-argued aspect, and the physical core of the warmth. Everyone agrees on the shape — the deep sub-bass is rolled off while the mid/upper-bass (~200–250 Hz) is lifted about 5 dB — but not on the result. One camp hears a warm, punchy, satisfying low end that's plenty for the price; another hears it as boxy, boomy and bleeding into the mids. A concrete gotcha both sides note: try to EQ the sub-bass back in and the driver audibly distorts.
Measured
Sub-bass rolls off from ~40 Hz; mid-bass elevated ~5 dB (DIY-Audio-Heaven). 2nd- and 3rd-order distortion reach audible ~1% in the bass, and a high-output-impedance source adds ~4 dB more mid-bass and turns it 'bloated and muddy.' SoundGuys warn sub-bass EQ boosts can push it into THD.
⚠ vs. listeners — The camps aren't disputing the graph — 'punchy/fun' and 'boxy/boomy' are opposite reactions to the same measured mid-bass lift over a rolled-off sub-bass. The sub-bass roll-off (and its tendency to distort when boosted) is common ground; only the valence of the mid-bass differs.
Where it splits
Warm, punchy and fun — reaches deep enough and gives an open-back a satisfying, un-fatiguing low end.52%
“Bass goes reasonably deep, even to sub levels, and it is punchy at the same time.”
Lieven, Headfonia
Boxy and boomy — a mid-bass hump that bleeds into the mids and thickens male voices, over a rolled-off sub-bass.48%
“The bass ‘bleeds’ into the mids which is most obvious with male voices which turn a bit ‘bloomy’.”
Solderdude, DIY-Audio-Heaven
Generally liked, with one recurring caveat. The midrange is warm, rich and musical, and vocals are a strength — but the warmth and the mid-bass lift round off the upper mids and can thicken or pinch male voices. Female vocals fare better; the net is a pleasant, slightly rounded presentation rather than a crisp, neutral one.
“The mids are extremely musical, rich and engaging and they have good spaciousness, separation and depth.”
Lieven, Headfonia
“Female vocals don’t suffer too much, but male vocals seem pinched and weighed down.”
Carroll Moore, Major HiFi
Measured
The response slopes down from 200 Hz to ~2 kHz, warming and slightly thickening the mids; the mid-bass lift bleeds into lower male vocals (DIY-Audio-Heaven).
Smooth and easy — the most agreed-upon virtue after comfort. The treble is relaxed and non-fatiguing, never harsh or sibilant, which is why owners can wear it all day. The trade-off, acknowledged widely, is that it's a touch rolled-off and less extended than pricier Sennheisers, so cymbals and air can read soft or slightly hollow rather than sparkly.
“Treble is ‘soft’ and sounds pleasant. It is never harsh nor sibilant but is not as ‘refined’ as that of the HD650.”
Solderdude, DIY-Audio-Heaven
“Even without EQ they’re fun, they will absolutely never give you treble fatigue, like it’s so easy to wear them and listen with them all day.”
GrimTurtle666 (r/headphones)
Measured
Fairly flat from ~1–15 kHz and extends beyond 20 kHz (DIY-Audio-Heaven); relative to the lifted bass, HiFi Oasis note 'cymbals and snares can sound a bit hollow.'
Soundstage
Contested · 6 srcGenuinely split, and it tracks what you compare it to. Against cheaper closed-backs and the HD 560S, many owners hear it as notably wide and deep — a highlight, and a big reason it's a gaming and movie favourite. Against pricier open-backs (or on the measurement bench), reviewers find it a little intimate and closed-in, not the wide stage the marketing implies.
Measured
No stage measurement is definitive, but DIY-Audio-Heaven's listening notes and Major HiFi both describe a somewhat close, 'leaning to congested' presentation, while owners comparing to the HD 560S consistently report more perceived depth.
Where it splits
Intimate and a touch congested — decent but leaning closed-in, and narrower than pricier open-backs.55%
“It lacks a bit in ‘open-ness’ of the sound.”
Solderdude, DIY-Audio-Heaven
Wide and deep — a real highlight for the price, with genuine depth and great for gaming.45%
“it presents a very balanced soundstage, as it has width, but also depth. This is rare for sennheiser headphones”
Thememefactory7 (r/headphones)
A quiet strength and the other half of the gaming appeal. Placement is described as accurate and precise, with good separation for the price — enough that owners reach for it in games and for spatial listening, even when they're lukewarm on the wider stage.
“Imaging is also spot on, it is extremely accurate. This would be a great gaming headphone.”
Thememefactory7 (r/headphones)
“The HD 599 also delivers excellent gaming performance with accurate sound imaging that helps players pinpoint in-game audio cues.”
HiFi Oasis
Okay for the class, not a selling point. It resolves enough to enjoy, but the warmth veils fine detail and it clearly trails the HD 6XX/600 and pricier references. Complex, busy passages are where the emphasized low-mids can smear things — this is a relaxed listen, not a revealing one.
“The warmth hides some detail however, and they are not as detailed as 6XX from my experience.”
Thememefactory7 (r/headphones)
“the emphasized low-mids can hide details in complex music.”
HiFi Oasis
Measured
DIY-Audio-Heaven note it shows the finest nuances a bit less than the HD 650, consistent with the warmer tilt and softer treble.
Modest and relaxed rather than punchy. There's decent mid-bass impact, but reviewers note it's a touch slow and soft compared with pricier Sennheisers, and the rolled-off sub-bass limits outright slam. Fitting for the cozy, easygoing character — no one buys it for the hit.
“Speed and attack are pretty good but compared to the HD600 they’re a tad slower of course.”
Lieven, Headfonia
“Decent impact/slam.”
SDLiu4 (r/headphones)
Measured
DIY-Audio-Heaven's step response shows a well-damped driver whose initial rise doesn't fully reach level — a slight lack of 'speed.'
Light and durable, but unmistakably plastic. The all-plastic chassis feels a little flexible and less premium than pricier Sennheisers, and owners caution against tossing it in a bag — yet it's reported as reliable, with removable velour pads and detachable cables. The catch is a proprietary 2.5 mm twist-lock cable that limits aftermarket options.
“the HD599 has a very light and plastic feel to it and the headphone band does bend in a lot of ways.”
Lieven, Headfonia
“all plastic, don't throw them in a bag with a bunch of books, but well-made”
thelubbershole (r/headphones)
Measured
~250 g; ships with two detachable cables (3 m to 6.3 mm and 1.2 m to 3.5 mm) via a single-sided 2.5 mm twist-lock connector; velour pads are user-replaceable (DIY-Audio-Heaven).
Isolation
Strong consensus · 3 srcOpen-back by design: essentially no passive isolation, and it leaks freely both ways. Expected for the type and not a flaw, but it rules out commutes and shared rooms — a quiet-room headphone.
“Its open-back design offers almost no isolation and limits where you can use it.”
Jasper Lastoria, SoundGuys
“And be warned, the bleed is real, folks.”
Carroll Moore, Major HiFi
Beloved on sale, second-guessed at list — the other real debate. Nearly everyone agrees it's a superb buy when it dips to ~$80–130, one of the best cheap open-backs going. At full price the case gets harder: the more neutral HD 560S is cheaper, the HD 6XX sits just above, and the newer HD 550/505 now crowd it. What you pay decides which camp you're in.
Where it splits
A steal on sale — one of the best budget open-backs when it drops to ~$80–130.52%
“They’re even better when they go on sale at $80, it’s one of the best budget buys in Head-Fi when it does.”
Regular-Cheetah-8095 (r/headphones)
Overshadowed at list — its own cheaper and newer siblings sound as good or more accurate for the money.48%
“While both the Sennheiser HD 505 and Sennheiser HD 550 are more expensive than the HD 599: they both sound very good by comparison.”
Jasper Lastoria, SoundGuys
