By aspect — in detail
Mids
Strong consensus · 7 srcThe strongest point of agreement and the reason the 600-series badge sticks. Sources across the spectrum — including the review most critical of the headphone overall — single out the midrange as its best quality: natural, textured, three-dimensional vocals with excellent note definition. The only caveat is a mild forwardness around 1–2 kHz that can push vocals and snares slightly shouty on some heads.
“Vocals are beautifully sculpted and well lit in 3D, as you might expect, organically presented.”
audioreviews.org (Jürgen Kraus)
“Natural, dynamic, detailed sound”
What Hi-Fi?
“The mids are generally natural, though a mild forwardness between 1-2 kHz and low-treble energy around 3-4 kHz can make vocals and snares sound slightly shouty.”
headphones.com (Andrew Park)
Measured
Sennheiser's own tuning notes claim a deliberate lift in the upper mids for vocal presence. headphones.com's B&K 5128 confirms a mild 1–2 kHz forwardness — and warns that this exact region swings most with fit: it is “prone to significant variation based on the coupling/orientation/clamp of the headphone,” so anyone EQing here should do it by ear rather than by graph. Kraus, who dislikes the headphone overall, still rates the midrange as beating Bose and its peers outright.
Tonality
Contested · 10 srcThe axis everything else turns on. Both measurement rigs agree the HDB 630 tracks a target curve more closely than any mainstream wireless rival — and sources split on whether that is the whole point or the whole problem. One camp hears the most correct tuning in the category; the other hears a headphone so evenly balanced that nothing stands out, and calls it boring. The split tracks what you want a headphone to do, not what the graph says.
Measured
RTINGS reads Sound Signature “Balanced,” Bass Amount “Slightly Emphasized (2 dB)” and Treble Amount “Balanced (-1 dB).” headphones.com measures “excellent wideband balance with a few quirks” on a B&K 5128. SoundGuys scores MDAQS Timbre 4.7 and Overall 4.6, and finds it “does a damned fine job of matching a palatable response.”
⚠ vs. listeners — The graph itself is barely in dispute — this is a near-target tuning. What splits reviewers is whether target conformity is the goal, which is a preference question a measurement cannot settle. The one source that disputes the graph (a Reddit listener who heard the default as “very bass heavy, not even close to neutral”) auditioned a store demo unit, and commenters in the same thread raised the obvious explanation: the app's bass boost may have been left switched on by a previous listener.
Where it splits
Genuinely, measurably balanced — the most correct tuning in wireless, and right out of the box.71%
“Incredibly balanced sound that suits every kind of audio.”
RTINGS
Accurate but uninvolving — so evenly balanced that nothing stands out, and plenty of listeners hear it as flat and boring.29%
“For every one person who considers the HDB 630 to be the last word in transparency, there might be two people who think it sounds uninvolving.”
Darko.audio (John Darko)
Genuinely three-way split, and the disagreement is about character rather than quantity. The measured level is only slightly above neutral, so almost nobody calls it bloated — but one camp hears that restraint as tight, quick and articulate, another hears it as slow, soft and undernourished next to the Momentum 4's push, and a lone listener heard outright bass bloat. The app's bass boost is the recurring fix for anyone in the second camp.
Measured
RTINGS measures Bass Amount “Slightly Emphasized (2 dB)” — a hair above neutral, not a consumer shelf. SoundGuys attributes its slightly lower MDAQS Timbre score to “the light bass” and reached for the app's bass boost on Barry White and Isaac Hayes. Darko found the Momentum 4's sub-100 Hz elevation gone entirely and toggled the boost to get it back — noting the same boost turns Om Unit's electronica muddy, so it is material-dependent. headphones.com adds that the ANC's active feedback loop means the sub-800 Hz response you measure is close to what you actually hear.
⚠ vs. listeners — The measurements sit between the camps rather than settling them: +2 dB is too little to support “bass heavy” and too much to support “bass light,” which is why the argument is really about attack and decay — qualities a frequency response graph does not capture. The lone bass-heavy read came from a store demo whose EQ state was unknown.
Where it splits
Tight, articulate and physical — quick and controlled, with real sub-bass reach and no bloat.55%
“Bass is its standout strength—tight, articulate, and physical without boom or bloat.”
headphones.com (Andrew Park)
Slow and subdued — it digs deep but lacks focus, crispness and punch; some material sounds undernourished without the bass boost.36%
“Yes, the HDB 630 digs deep into the sub-bass but the low end lack focus, it is sloppy.”
audioreviews.org (Jürgen Kraus)
The outlier read: too much bass out of the box — bloated rather than neutral.9%
“The default tuning is also very bass heavy, not even close to neutral”
Reddit r/headphones
Contested, and it splits on tolerance for a safe top end. Most reviewers hear highs that are clean, balanced and specifically engineered not to fatigue — the top octaves sit slightly under. A substantial minority, including the most measurement-literate source, hears that same restraint as a mid-treble dip that leaves the presentation closed-in and short of air.
Measured
RTINGS measures Treble Amount “Balanced (-1 dB).” SoundGuys finds “the uppermost octaves are a little underemphasized, but otherwise inoffensive,” and advises a shelf filter rather than a peak boost if you want them back. headphones.com hears plenty of upper-air sparkle but a dip through the mid-treble, and Kraus — testing with the Cowboy Junkies — reports he “can barely hear the cymbals from behind the bass,” concluding the tuner took the treble back to an “über safe level.”
Where it splits
Safe, clean and non-fatiguing — detailed without ever turning bright, harsh or sibilant.68%
“tracks with a lot of content above 4kHz should be pretty well-represented, while preventing overstimulation or listening fatigue associated with high levels in these frequencies.”
SoundGuys (Christian Thomas)
Too safe — a mid-treble dip leaves it closed-in and stuffy, missing air and sparkle.32%
“Treble is where opinions are likely to diverge with any headphone, and it’s where the HDB 630 ended up disappointing me a bit.”
headphones.com (Andrew Park)
Broadly praised, with the disagreement being about the yardstick rather than the headphone. Against wireless rivals it is repeatedly called the class leader — cleaner and more separated than the AirPods Max, Sony XM6 and Bose QC Ultra. Against wired audiophile gear, the critical camp finds it merely competent, an incremental step rather than the revolution some video reviewers claimed.
“Layer separation and transparency emerge as the HDB 630’s defining characteristics.”
Darko.audio (John Darko)
“The HDB 630 are miles ahead when it comes to detail, dynamic expression and refinement.”
What Hi-Fi?
“Without EQ, the HDB 630 already outperforms nearly every major wireless ANC headphone in its class.”
headphones.com (Andrew Park)
Measured
RTINGS credits “amazingly well-matched left and right drivers” and an impressive peaks-and-dips result; SoundGuys scores MDAQS Distortion 3.8, and Headfonia reports no distortion even at maximum volume. Sennheiser builds these 42 mm drivers at its Tullamore plant in Ireland (the Momentum 4's come from China) with extra damping to cut closed-back backwave reflections — Darko notes the claim of tighter tolerances and better driver matching, which the RTINGS channel-matching result supports.
Well-liked overall, with one specific and repeatable exception. Reviewers agree the clamp is moderate, the weight distribution good and the deep pleather pads easy for hours — including over glasses, which the improved seal actively helps. But the pad openings are small, and listeners with larger ears report real pain; the recurring owner fix is to extend the headband so the cups sit lower. Two smaller notes: thin headband padding, and warmer ears than the Momentum 4.
“Because the mass is manageable and the padding is so thick, the headphones are quite comfortable to wear for long periods of time.”
SoundGuys (Christian Thomas)
“Comfort—for me, at least—is improved over the Momentum 4 thanks to reduced clamp force and better weight distribution, but large-eared listeners may still find the small-ish earpad openings too tight.”
headphones.com (Andrew Park)
“Padding around the middle of the headband is a little thin.”
RTINGS
Measured
311 g by Sennheiser's own spec, confirmed by What Hi-Fi and by Darko's note of an “18g weight increase over the Momentum 4's 293g” — mid-pack for a wireless over-ear, with no IP rating. RTINGS' headline con is mechanical rather than sonic: “Poor frequency response consistency (FRC) means you need to take time getting the proper fit with each wear.” headphones.com independently corroborates it on a B&K 5128 and adds that the cups swivel so freely that slight asymmetry on the head shifts tonal balance — so on this headphone, comfort and sound are the same variable.
Soundstage
Contested · 7 srcContested, and it tracks the comparison you make. Against wireless rivals and the Momentum 4, most reviewers hear a genuine step up — wider, pushed forward of the head, occasionally described as near open-back. Against open-backs and wired references, the critical camp hears an ordinary closed-back: not congested, but not airy either. The optional crossfeed narrows the stage as often as it helps.
Measured
SoundGuys scores MDAQS Immersiveness 4.0 — good, not exceptional. RTINGS dropped its Virtual Soundstage test in Test Bench 2.3, so there is no direct lab figure. Darko credits part of the width to the crossfeed feature (run on “low”), while an owner testing it found it narrows the stage on well-mixed stereo material and only helps hard-panned older recordings — so some of this split may simply be different crossfeed settings.
Where it splits
A real step up for a closed wireless can — wide, and projected in front of you rather than ear-to-ear.73%
“the HDB 630 paints its stage like a motorcycle helmet’s visor – a wider arc positioned slightly in front of the listener.”
Darko.audio (John Darko)
Merely adequate — average width and depth, and still audibly a closed-back next to real open headphones.27%
“Staging is not overly wide and not overly deep, but also not claustrophobic.”
audioreviews.org (Jürgen Kraus)
Isolation
Contested · 9 srcThe most evenly split aspect, and there is a measurement that explains why. The deep pads seal well and block a lot passively, so sources judging the whole package call the quiet excellent. Sources judging the ANC circuit itself find it a clear step behind Sony, Bose and Apple — because it is essentially the Momentum 4's circuit. Everyone agrees it handles steady low rumble and wind well, and that it is not the reason to buy these.
Measured
SoundGuys measures the ANC removing about 80–84% of noise (fit dependent) and identifies the reason the camps disagree: “a lot of the improvement in the performance over the Sennheiser Momentum 4 Wireless is achieved on the back of the superior isolation, as the effect of the ANC unit itself is extremely similar between both models.” RTINGS rates the ANC excellent overall but lists “ANC struggles in the low-bass” as a con. Darko finds wind-noise handling a genuine strength. Sennheiser's own marketing calls the ANC “flawless,” which no independent source supports.
⚠ vs. listeners — Both camps are measuring real things. The passive seal genuinely improved over the Momentum 4; the active circuit genuinely did not. Reviewers who weigh total quiet land positive, reviewers who weigh the electronics against Sony and Bose land negative — and because the seal does the work, results swing with fit, hair and glasses more than on rivals.
Where it splits
Excellent in practice — the seal plus the ANC adds up to genuinely quiet, and it is adjustable.45%
“ANC is generally excellent.”
RTINGS
The weak spot — good, not great, and a clear step behind the Sony, Bose and Apple leaders at this price.55%
“Just as it is with the Sennheiser Momentum 4 Wireless, ANC is a sore spot.”
SoundGuys (Christian Thomas)
The sharpest disagreement, and it is not really about sound. One camp notes it out-tunes every mainstream rival while costing the same or less, and throws in a $50 dongle and a parametric EQ nobody else offers. The other notes the plastics, chassis and comfort are the half-price Momentum 4's, the battery is sealed in, and an ordinary-if-accurate tonality has been moved into the premium bracket. Several reviewers hold both views and still recommend the cheaper model to most people.
Measured
$499.95 / £399.90 / €499.90 at launch and still $499.95 on Sennheiser's own store, against the Sony WH-1000XM6 ($450), Bowers & Wilkins Px7 S3 ($449) and Bose QuietComfort Ultra 2nd Gen ($429) — and against its own sibling, the Momentum 4 Wireless, now $249.95–$299.95. The bundled BTD 700 dongle sells separately for about €50. What Hi-Fi calls the package “competitively priced” and awards five stars; Kraus counters that at this price he expects spatial audio and a user-replaceable battery, calling the sealed battery “planned obsolescence.”
Where it splits
Fairly priced — best-in-class sound for the same money as, or less than, the Sony/Bose/Focal alternatives.64%
“Of the three, the Sennheiser have the most balanced, controlled sound, and manages this while being cheaper than either rival.”
RTINGS
Hard to justify — the same plastics as the half-price Momentum 4, with the upgrades all in software.36%
“At €499, the HDB 630 occupies an awkward position.”
Darko.audio (John Darko)
Solid but argued over, and the argument is about expectations rather than defects. Nobody reports creaks, wobble or QC problems — tolerances are repeatedly called excellent, the pads are user-replaceable and the case is genuinely good. The complaint is that at $500 it is the same plastic as the half-price Momentum 4, with a sealed-in battery and a plain look.
“But fans of discreet, minimalist design will more readily appreciate their subtly shiny matte finish and quality construction.”
What Hi-Fi?
“It lacks the premium materials expected at this level – the plastic construction feels identical to the €250 Momentum 4.”
Darko.audio (John Darko)
“Planned obsolescence not acceptable at this price”
audioreviews.org (Jürgen Kraus)
Measured
SoundGuys scores durability 7.5/10 with no IP rating; What Hi-Fi scores Build 4/5 and lists “Plain-looking design” as a con. Headfonia reports “build tolerances are excellent, hinges feel reliable, and there’s not a single creak or wobble, even when twisting the headband,” while noting it is still plastic throughout. The pads come off and can be replaced; the battery cannot, which is Kraus's core objection — his 2007 Sennheiser PXC 450 still runs on a slid-in AAA.
Well-regarded and lightly disputed. Instrument placement and separation are consistently called precise for a closed wireless headphone — helped by unusually well-matched drivers — with one critical listener finding it short of the mark. Kraus adds the useful condition that separation holds up as long as the low end stays controlled.
“Spatial cues and instrument placement are good and so is instrument separation as long as the low end is kept in check.”
audioreviews.org (Jürgen Kraus)
“Instruments panned hard left or right track with superior clarity.”
Darko.audio (John Darko)
Measured
RTINGS credits “amazingly well-matched left and right drivers” — channel matching is one of the headphone's strongest lab results, and Sennheiser attributes it to the Tullamore driver line. Headfonia reports imaging that “feels almost open-back-like at times.”
Dynamics
Contested · 5 srcGenuinely split, and it is the same argument as the tonality one wearing different clothes. One camp hears shape, drive and sharply defined attack; the other hears a headphone that renders everything accurately but pushes nothing, with a soft leading edge that drains the excitement. Nobody disputes it is less immediately exciting than the Momentum 4.
Measured
No lab test isolates this, which is part of why it stays contested — SoundGuys' MDAQS Distortion score (3.8) and Headfonia's report of no distortion at maximum volume say the driver is clean, not whether it slams. Darko frames the same quality as a deliberate design choice rather than a flaw: the Momentum 4 adds “cream and sugar,” the HDB 630 serves the coffee black.
Where it splits
Dynamic and expressive — sharp attack, natural decay, and it follows a track's rises and falls.59%
“These are wonderfully smooth and natural sounding headphones, full of shape and dynamism across the frequency range”
What Hi-Fi?
Soft and toothless — accurate but flat, with an attack that retreats instead of hitting.41%
“This results in a somewhat toothless attack…more a retreat.”
audioreviews.org (Jürgen Kraus)
