Sound
Neutral
Also called neutrality, flat, reference tuning
A neutral product adds as little of its own color as possible, so recordings sound the way they were mixed. In practice it means a frequency response close to an accepted target, with no obvious bass or treble emphasis.
For speakers, neutral means a flat on-axis Frequency response with smooth, similar off-axis response, measured anechoically. For headphones there is no single answer, because a headphone that measures flat at the eardrum does not sound neutral; targets such as the Harman target and Diffuse-field curve are attempts to define what neutral should measure like.
Neutral is not the same as boring. Many listeners prefer it because it works on every genre; others find it polite and reach for a V-shaped or Warm tuning. Studio monitors and some Objectivist-leaning products aim for it.