Sennheiser HD 620S

Sources split: a small majority hear real, extended sub-bass the open 6-series never had, with good impact and control; the rest hear a restrained, mid-bass-tilted or boomy low end with little sub-bass punch. The split tracks the seal — on rigs and heads that seal it reaches deep, and a small leak from glasses, hair or the limited cup tilt strips most of it away.

Sources split: most hear a natural, clean and open Sennheiser midrange with no closed-back honk, and several call the mids the highlight; a sizeable minority hear the 400–800 Hz lift and scooped 1.5–2 kHz as boxy, honky or odd, especially on female vocals and piano. Even its fans rarely rate it as full or natural as the open HD 600 / 650.

Sources split three ways. Most hear smooth, airy, well-judged treble with no sibilance — for several it is the best part of the headphone. About a third hear it as sizzly, sharp or peaky on some tracks, and a few hear the opposite, a slightly dull or rolled-off top. The narrow 4 kHz notch and the lightly damped driver sit behind all three readings.

Sources split: roughly two-thirds call it near-neutral and balanced — close to the Harman target, not tilted hard in any direction — while a third hear an uneven, coloured signature (a w- or v-shape, a 'phone booth' boxiness, a 'weird' default sound). The labs mostly sit in the first camp; several experienced listeners who EQ everything sit in the second.

The headline feature, and broadly agreed: wide and unusually open for a closed-back, credited to the angled drivers. The disagreement is one of degree — many say it rivals open-backs, while the measurement labs and several reviewers hear 'wide for a closed-back' with average depth and plainly closed character.

“they provided a wide soundstage, more like what I would expect from an open-back design”

Mel Martin, Home Theater HiFi

“Is it like an open headphone? Absolutely not.”

Griffin Silver (Listener), Headphones.com

A consistent strength: stable, well-organised left–centre–right placement that reviewers and gamers single out. The caveats are fine separation ('fuzzy' instrument edges for Listener, 'just decent' on busy tracks for one owner) and the channel imbalance a few units show, which shifts the centre.

“Imaging is excellent.”

Mel Martin, Home Theater HiFi

“Staging and imaging are highlights of these headphones.”

Biodegraded, audioreviews.org

Good, with a caveat. Most reviewers call it clear and detailed for a closed-back — a recording engineer finds it more resolving than the HD 600 / 650 — but the more critical ear-by-ear reviewers say it isn't special for the price and that some of the 'detail' is the treble tilt talking.

“Detail/resolution and clarity, particularly from the upper mids and higher in the range, are very good; although some of this perception is likely due to the treble tilt in the frequency response”

Biodegraded, audioreviews.org

“the sense of “detail” here isn’t anything special for its price on my head”

Griffin Silver (Listener), Headphones.com

Sources split almost evenly. One camp hears crisp, punchy, engaging dynamics with tight bass slam; the other hears a soft, relaxed, low-contrast presentation that lacks punch — the most-repeated criticism in the mainstream and critical reviews. The same bass-seal and 1–2 kHz scoop effects likely drive both readings.

Sources split: most find it very comfortable — thick, soft pads with room for the ears, a well-padded headband and some of the most comfortable pads in the 6-series — while about a quarter find the clamp too firm, especially on larger heads or with glasses, or can't get the cups to sit flush against the jaw. Most agree the clamp eases with use, and the pleather pads run warm.

A strength for most: a mostly plastic 5-series frame stiffened with steel headband sliders and cup plates that reviewers call sturdy, even tank-like, with replaceable pads and cable. The caveats come from owners: channel imbalance on some units, a headband pad whose adhesive lets go after a year or so, the proprietary twist-lock cable, and microphonic cable and cups.

“the frame does feel a touch plasticky, but the reinforced metal in the headband and earcup housings make the whole arrangement feel sturdy”

What Hi-Fi?

“Sennheiser should do a much better QC on these $350 headphones.”

lc6, Audio Science Review forum

The reason to pick it over the open 6-series, and most sources rate it very good for a passive headphone — quiet enough to keep music private and blunt typing, fans and chatter. The labs are more reserved: RTINGS rates it middling and SoundGuys finds low rumble barely touched, so it is a home and office headphone, not a commuter.

“If you stand next to somebody using the HD 620S, you hear absolutely nothing, zilch, zero.”

Jürgen Kraus, audioreviews.org

“high-pitched background noise is somewhat muffled, though chit-chat and deep rumbles aren't strongly attenuated”

RTINGS

Sources split: about two-thirds call it the best passive closed-back near its price and a legitimate 6-series member — even its sharpest critic says it earns the badge — while a third treat it as a sidegrade you should skip for the cheaper, more refined open HD 600 / 6XX unless you need isolation, or as worth nearer $200–250 than its price. The list price has since risen from $349.95 to $399.95, though it usually sells for about $300.