Back in the 80s, harddriveless computers would exist slap bang under tvs.
But u knew that leaving a floppy disk on a tv could be dodgy.
Harddrives in 90s computers that used tvs were shielded - but this was radio shielding to prevent `noise`. No1 mentioned harddrives and magnets... but it should be mentioned.
Imo, unless u`r using a scientifically amplified 1jiggawatt induced coil magnet to experiment in time travel, without flux capacitors (which is silly really, every1 knows the flux is a required constant), the likes of a speaker (which I think u`r on about) next to a metalic pc case, shouldn`t effect the harddrive.
That`s not to say I wouldn`t recommend installing a drive inside a decent speaker cabinet.
And hey, alot of cases have a case speaker next to the drive bay.