Atma-sphere (no affiliation). Natural, not fatiguing, and the perception that you're listening to music- not a "system" or a stereo or even speakers for that matter (as Sounds Real Audio mentioned).
Objective characteristics would include flat frequency response across the audio spectrum (often extending to 100khz- to ensure flat response), Low distortion, transient response (high slew-rate) for dynamic range among others.
Objective characteristics would include flat frequency response across the audio spectrum (often extending to 100khz- to ensure flat response), Low distortion, transient response (high slew-rate) for dynamic range among others.