ehhh I'd say mostly solved. The problem of turning a recording into a perfect sound-wave replication is actually not easy, because the physical world is annoying with heat and friction and and physics.
I'd say 24/96 is comfortably the "end game solved problem" quality for source recordings though, not CD. Even if it is just for the baseline safety margin that it is easier to implement perfect filters with no transition bands anywhere near the audible frequencies, and that additional bit precision has no downside unless you get into accuracy problems with noise on the recording side.
From the speaker point of view, I think IEMs are the closest to being "solved", since the tiny drivers minimize the physics issues with larger drivers, they are probably closest to pure reproduction. For full-size speakers etc., pure reproduction can be accomplished for certain frequency ranges by individual drivers, but over the full range it is not so "solved", e.g. with bass there is often a physics issue with the kinetics of moving a large driver cone in perfect phase-sync with the relatively tiny and light tweeter.
I've actually been wondering if speaker cones are a possible application for graphene.
I'd say 24/96 is comfortably the "end game solved problem" quality for source recordings though, not CD. Even if it is just for the baseline safety margin that it is easier to implement perfect filters with no transition bands anywhere near the audible frequencies, and that additional bit precision has no downside unless you get into accuracy problems with noise on the recording side.
From the speaker point of view, I think IEMs are the closest to being "solved", since the tiny drivers minimize the physics issues with larger drivers, they are probably closest to pure reproduction. For full-size speakers etc., pure reproduction can be accomplished for certain frequency ranges by individual drivers, but over the full range it is not so "solved", e.g. with bass there is often a physics issue with the kinetics of moving a large driver cone in perfect phase-sync with the relatively tiny and light tweeter.
I've actually been wondering if speaker cones are a possible application for graphene.