So, the US SCD OST used QSound, which was supposed to create 3D surround sound by facing the speakers away from each other. Obviously, this does not work for headphones. I've been trying to search for DSPs that can specifically replicate this for headphones with little luck. I was curious if anyone who's more experienced with audio engineering might have a better clue of where to look. I think it'd be cool to set up a processed version of the US SCD OST for headphone users to hear the music as it was intended, a sort of preservation effort.
I hadn't even heard of QSound until I found this thread, where I wound up in a bit of a adventure of 90's "multimedia of the future" and the "information superhighway". Anyways, I went ahead and set myself up for QSound and had a good listen to Sonic CD's music to see how it uses QSound. Outside of the singers in Tidal Tempest spatially being a bit higher than where I think my speakers are and the curious instances of odd panning and the time travel jingle swirling around me, QSound doesn't really seem to be heavily used a ton in Sonic CD's music? At best, it sounded a bit strange in-game coupled with the panning rings and the other sound effects. At worst, I couldn't hear a difference when I listened to the music again with headphones (outside of the stereo being slightly flat). So whether you're using stereo speakers or headphones, Sonic CD's music doesn't really have anything massive compared to the other QSound examples that I've heard elsewhere (street fighter zero 2 alpha for the arcade is a good example). To answer your question though, I don't have anything on QSound-to-regular-stereo mixing. In fact, it seems that QSound is literally so obsolete that there's really only information about it surface-level and from anecdotes! Not a good sign for something that's rather obscure nowadays. If anything, that's a bad sign. "Near-extinct language" levels of bad sign. Your best bet is to just... use stereo speakers or headphones. Sorry.
That's not how QSound works. It is meant to work with a "traditional" speaker setup. They just need to be positioned enough apart for your ears to be able to differentiate between each speaker enough (I think it was suggested at least half a metre for computer speakers, for example, and there was a 50- 75cm gap between the speakers on most Capcom cabs from what I recall.) When the gap gets wider (such as a Hi Fi environment) it's recommended to point them slightly inward, in fact. If you did face them outward, I think the effect would be somewhat diminished, as it uses an algorithm to figure out what volume and delay/phase would be heard from either ear at a set position, by taking your head into account, for that to work, you need to point the speakers forwards so the sound is going past your ears correctly. The problem is when the sound is going directly into you ears, such as headphones, that also diminishes the effect, it'll still sound "wider", but you lose a lot of the positional nuance. QSound created a new algorithm for headphones to get past that eventually, Q2, the problem is pre-recorded material is encoded with Qsound at mixdown, obviously, and most prerecorded stuff was recorded in the original algorithm. I honestly don't think a DSP will ever get a Q1 recording to sound precisely how it's supposed to through speakers when using headphones. There was a competing technology used on a few albums (and apparently used on some Megal LD games) called Roland Sound Space that worked far, FAR better on a headphone level. Examples of RSS here (although compression can also somewhat screw with 3D audio, so don't expect miracles)
