It's been 12 years, but I once wrote a blog post on how my commercial spatial audio effect works: https://hajo.me/blog/2014/12/28/how-surround-sound-for-headp...

BTW, the resulting plugin was used during mastering of George Lucas' Red Tails, so I guess sound quality was fine ;)

My own Mac app has long since been discontinued (because Apple locked me out of the KExt permission), but I sold the tech and it lives on.

I keep wondering if I should build hardware headphones with the spatial audio inside, so it looks like Dolby Atmos to the TV but then does virtual surround sound on your headphones, but hardware has low-ish margins so I never found anyone willing to fund it, even though I already have a working prototype. Oh and the audio engineer who invented it has since been Grammy-nominated twice. And, well, Hollywood likes it. But still a tough sell towards investors.