Band: opinion spread · Dot: weighted average
Sources split, though not evenly. Most reviewers and two flat-target benches hear an unhyped, close-to-neutral balance. A smaller camp of listeners, a Harman-target reviewer and some owners hear it as dark and dull. The graphs agree on the shape; the disagreement is over the reference, plus how the cups sit.
Measured
Five rigs against the same rig's HD 600: 5–9 dB more output at 20 Hz, level from 100 Hz to 1 kHz, 2.5–6.5 dB less at 1.5–3 kHz and 1–10 dB less from 5–8 kHz. Against the Harman over-ear target (oratory1990, GRAS) it sits 2–6 dB short below 50 Hz, about 4 dB low at 2 kHz and 3.5–12 dB low from 6–10 kHz. DIY-Audio-Heaven's flat-plate bench puts it within ±3 dB of a flat target from 20 Hz to 22 kHz.
vs. listeners — Both camps are reading the same curve against different yardsticks: it is near-flat by a flat-plate or monitor-matching reference and dark by the Harman target. Unit variation adds to it — Sonarworks found pairs within ±2 dB except ±4 dB around 6 kHz across eight units, and listener's two samples differ by 2–3 dB from 1.5 to 6 kHz.
“Designed especially for studio use, Neumann’s NDH 30s offer exceptional clarity and a neutral, unhyped frequency response.”
Sam Inglis, Sound On Sound
“I'm notoriously treble sensitive, but the NDH30 is among the darkest headphones I've ever heard”
listener (squig.link measurer), r/headphones
