The 660s are resolving enough when I am actively seeking for detail, dark enough to not distract me when I am doing something else, good vocal presence to put forward the voice when I am listening to a podcast, rewatching a lecture, or watching a YouTube video while doing something else, Not as shouty as other midrange focused headphones to fatigue me, Breathable enough to not sweat at all, Light enough to be worn forever, Durable enough to last forever, Good enough imaging for gaming, And natural timbre to allow me to focus on the sound/music instead of the device, Wide enough soundstage to not feel in my head but also intimate for things to also sound presented right to me
Sorry for formatting
im pretty sure i can hear a good amount past 20khz if its the only sound, but otherwise its indiscernible and im pretty young too