Audio Technica ATH-W3000ANV CSD Waterfall Plots. Not the cleanest.
I will give 50 % contrary view to "not the cleanest" judgment, 50 % and not a flat disagreement. The assessment 'clean' somehow does not fully relate to the resulting sound made by the driver and the resonance chamber of these headphones. Yes, the notes have longer decay than what would be a norm for 'clean' sounding headphones but the prolonged reverberations consist of what surely sounds like extra set of lingering harmonic series overtones. The notes sound thicker [but not in overdone way] because of their longer, shall I say, 'HARMONIC decay'. The important and unmeasured thing is what prolonged reverberations are made of, they can make headphones sound screechy or melodic. Despite the fact that W3000 do not measure top 'clean' they do sound very clean, one does not hear uncontrolled unpleasant dissonances. These headphones have one amazing tuning.