> Why would speakers be any different than earphones

There are various "ideal" EQ targets for earphones depending on what your model of an ideal audio source is. They all start with a flat response speaker, from then you can model:

- Two speakers right next to the listener's ears. (flat)

- A single speaker 1 metre away in the x axis, in an infinitely-sized anechoic room. (free field)

- Two speakers 30 cm away pointing to a plastic torso at a 90° angle, in a room with reverberations. (B&K/Harman)

- A spherical room lined with speakers, point listener in the centre with no reverberation. (diffuse field)

- An infinite wall of speakers 1 metre away in the x axis. (another method for free field)

- etc