The upgraded Haaze v2 from Klevgrand is an elegant solution for controlling stereo width and spatially positioning a sound in a stereo mix. Regular L-R panning is a weak tool that doesn't resemble real-world acoustics, which becomes clear when trying to place a mono sound naturally in a stereo mix (especially on headphones). The result still feels very "mono". Haaze is an audio plugin that makes the positioning feel more natural, understandable and pleasant for the ears. It splits the audio signal into 16 frequency bands. On each band, you can delay the left or right signal (which will make the listener believe the sound arrives from the side that’s reaching the ear first), pan it to the left or right, or adjust the overall width on that band (for example, make the lower frequencies more focused in the middle than the higher). Haaze can also diffuse a mono signal and make it wider.
If this sounds complicated, Haaze comes with many presets that will help you to get started. It sounds good both in headphones and loudspeakers, and it has great mono compatibility.