I think there's more to speech than just the hyoid bone. Neanderthal man (and woman) had, in comparison to today:
a different shaped (flatter from memory) palate
a larger tongue
a larger jaw
higher (as in nearer the top) vocal cords
less well developed (hence less controllable) musculature in the oropharynx and nasopharynx

And of course they had much less to talk about...