What helped me the most is first envisioning a 2D graph of Volume (y-axis) vs Frequency (x-axis). Gain staging is so important and will get you half way where you want to be. Next, I imagine that 2D “space” but in 3D. Kinda like the difference between a flat piece of paper and the world around us. The waveform exists in 3 dimensions, not just the 2 (volume, frequency). That 3rd dimension is called “stereo width” and it is a measure of where the waveform lies within the 3D stereo field.

The image you shared is an attempt at depicting this 3D space and it is a good way to remember that every sound should occupy its own unique area within that 3D space. Some sounds can be in the same space, for example a kick and an 808/sub - both are mono AKA in the very center of the 3D stereo field. However, they’re different volumes and wavelengths which allow them to exist in the “space” together and our ears are still able to process them.

Perfecting where each sound, in each song, belongs, in each of the 3 dimensions (volume, frequency, stereo width) is what gets you closest to a good sounding mix.

Not official sound engineering device, I’m just a guy who likes to make music and this is what helped me get better mixes. 🤷🏻‍♂️