Superlux HD 660 Pro

Sources split, and the split is about tolerance rather than fact: every curve shows a peak around 6–8 kHz. The larger camp — both measuring reviewers, the lowest-rated owner reviews, Reddit's sharpest critic — hears it as sharp, sibilant or metallic and says it needs EQ or a tissue in front of the driver. The smaller camp, led by headphonecheck and a good share of owners, hears open, detailed highs that stop short of harsh. Several in both camps note that the same lift is what makes it useful for spotting flaws while tracking.

Sources split three ways. Most owners, and DIY-Audio-Heaven by ear, hear too little: thin, short of punch, missing the lowest notes — the single most common complaint in the lowest-rated reviews. A smaller group led by headphonecheck hears bass that reaches deep without being pushed. And the two reviewers who took it apart, Audiofanzine and Custom Cans, hear plenty of bass that is loose and uneven rather than missing. The measurements side with 'plenty' — which makes fit and the treble peak the likely reasons so many hear so little.

Sources split. A small majority by weight — headphonecheck, most video reviewers and over half the owners who describe the balance — call it clean, even and honest enough for monitoring. The rest, led by the two reviewers who measured it, call it bright, thin or hollow, fine as a magnifying glass on a recording but wrong for mixing or for relaxed listening unless you equalise it. Owners who do EQ it tend to say it sounds much better afterwards.

The steadiest part of the sound. Reviewers who measured it and reviewers who only listened agree the midrange is even, clear and not pushed forward, with voices easy to follow. The dissent is at the edges: a few low-rated owner reviews call the mids missing or tinny, which reads as the treble peak colouring everything above them.

“Mids are fairly neutral, dynamic and ‘open’ sounding and have good clarity.”

DIY-Audio-Heaven (Solderdude)

Wide for a closed-back at this price, by broad agreement — reviewers and owners alike describe real width and a sense of the room, helped by the forward treble. Compared directly with a DT 770 Pro, opinion goes both ways: Custom Cans thought the Superlux possibly wider, two owners heard the Beyerdynamic as the more spacious.

“sound staging on these is possibly better than the dt770”

Custom Cans (Jason, YouTube)

“In addition, the headphones offer a surprisingly wide soundstage for a closed-back model.”

Phillip Ebert, Thomann owner review (32 Ω)

Sources split, on a thin base. Headphonecheck and the owners who game on it report clear placement and easy direction-finding. Against that, one Reddit reviewer found his pair's left and right channels unbalanced, and the measurements and owner reports suggest that is a matter of which pair you get rather than of the design.

High for the money, and widely said so — but it is detail of the spotlight kind. Reviewers credit the treble lift for the articulation: consonants, breaths, cymbals and reverb tails are pushed forward, which is what you want when checking a take. Set beside a DT 770 Pro, most who own both hear the Beyerdynamic as the more resolving.

“They are quite bright though, with lots of clarity in the high end.”

technically_not, Thomann owner review (150 Ω)

“The Beyers have much better detail, depth, soundstage and FAR better low extension but I guess this is to be expected at this price.”

TERD, Thomann owner review (150 Ω)

Mixed, and thinly covered. Headphonecheck heard punchy transients and DIY-Audio-Heaven a dynamic midrange; Audiofanzine found attacks precise but the overall delivery heavy-footed. At the bottom end a couple of owners report the bass compressing or saturating on sub-heavy music played loud, which matches the distortion measured there.

“Transients in particular are reproduced with punch.”

headphonecheck.com (Carsten Kaiser)

“the bass is so wrong and kick drums come out extremely loud and compressed”

boudou701, Thomann owner review (32 Ω)

The most consistently praised thing about it. Soft velour pads, a padded headband and under 290 g on the head let most owners wear it for hours, and several rate it close to the DT 770 it copies. The exceptions are specific: Audiofanzine found it pressed above the ears, a few owners with large heads or particular head shapes got pain or gaps under the ear, the pads run warm, and two reviewers found them firmer or scratchier than Beyerdynamic's.

“Nearly as good as the beyerdynamics, which are the most comfortable pair of headphones I have ever worn.”

technically_not, Thomann owner review (150 Ω)

“The fit of the headphones is excellent.”

headphonecheck.com (Carsten Kaiser)

Sources split, and not simply press against owners. Audiofanzine opened one and found blobbed solder joints, knotted wires, glue and yokes it could bend by hand; Custom Cans' teardown found lighter metal and rougher stamping than the Beyerdynamic but a sound copy. Owners divide the same way: many report sharp unfinished edges on the metal, a thin cable, glossy cups that collect fingerprints and a handful of failures — a dead channel, crackling or rattling within a year — while others have used theirs for years in studios and gig bags. The cable is fixed.

Decent for a closed-back, with a fit caveat. Most reviewers and owners find it blocks enough and leaks little enough for tracking next to a microphone, and several put it level with a DT 770 Pro. A minority find it lets more through than a closed headphone should — where the cups don't sit flush under the ears, it does.

“Isolation from outside noises is decent to good.”

DIY-Audio-Heaven (Solderdude)

“they are WAY less isolated, more like semi-open than closed”

boudou701, Thomann owner review (32 Ω)

Sources split, with the larger camp clear. Most owners and video reviewers, and headphonecheck, call it remarkable for £30 or $45: a comfortable closed-back that does a studio job. The dissent is firm, though — Audiofanzine gave it 4 out of 10 on the strength of its construction, DIY-Audio-Heaven says a DT 770 is worth the difference, and the lowest-rated owners say buying cheap meant buying twice. Both camps tend to agree it makes more sense as a tracking or spare pair than as an only headphone for music.