It mostly comes down to mastering. Some hi-res versions use a different master than the CD, which can affect volume and dynamics. If the hi-res version has less compression or peak limiting, it might sound quieter but more natural. EQ differences can also change the perceived impact. Some DACs handle hi-res files differently, which can affect playback. And sometimes, expectations play a role—if a hi-res version is just cleaner rather than dramatically different, it might seem less engaging. The best hi-res releases keep the original dynamics while adding clarity.
Why some streaming hi res versions are lower SPL
Why is it that some hi res versions of cd red book music sound quieter and less dynamic/ engaging while others deliver everything you’d want? Namely full volume and dynamics which are identical to the original cd version but with the added resolution expected of the format.