Band: opinion spread · Dot: weighted average
Sources split, and it's the most-argued point. About half — editorial reviewers and owners alike — hear a smooth, controlled, non-fatiguing top end with enough air. A large minority, led by treble-sensitive listeners, hears occasional sharpness, sibilance or a hot spot in the upper mids and lower treble, worse at high volume, on cheap dongles or with wide-bore tips. A smaller group finds it too polite, lacking sparkle. Measurements explain the split: the 4–6 kHz region sits well under target, then a peak near 8 kHz comes back to target level, and insertion depth and tips move both.
Measured
Across 28 IEC-711-class rigs the 4–6 kHz band sits about 4 dB under the Harman in-ear target (2.4–6.4 dB), then a peak near 8 kHz (6.5–9.5 kHz) returns to roughly target level (+5.5 dB re 500 Hz, median); 10–15 kHz runs about 2.5 dB over target. The B&K 5128 rig (Fox Told Me So) reads the whole top end brighter. Deeper insertion cuts 4–6 kHz by 2–3.5 dB (Super*, ATechReviews); the stock foam tips cut 10–16 kHz by about 2.5 dB (boizoff) and Final Type E tips cut 6–10 kHz by about 2 dB (IEM Ocean). Source impedance barely moves it (Audio Amigo, 15 Ω).
vs. listeners — The level above 6 kHz is close to the target, so 'harsh' is not excess treble; what listeners react to is the contrast between the relaxed 4–6 kHz dip and the 8 kHz peak, which shifts with fit, tips and volume. The same curve reads as 'smooth' to most and 'spiky' to treble-sensitive ears.
“It does exactly what it needs to do to balance out that dynamic bass boost without giving you sibilance or fatigue.”
Audio Amigo (YouTube)
“but does so without the subtle harshness that the Tea Pro sometimes displays”
Resonance Reviews (Aaron)
“The treble response is lacking in terms of amount”
avishifi (avishai.squig.link), Head-Fi
