A De-Esser is essential when recording voices, particularly when using a condenser microphone or when recording your Grannie when she has her teeth out.
Paul White editor of Sound on Sound wrote the following when he reviewed the Drawmer MX50 De-Esser
" The MX50 can emulate basic full‑band de‑essing, but more interestingly, it also features a split‑band compression mode where only frequencies above a split point set by the user are attenuated. This isn't quite as sophisticated as precisely notching out only the sibilant band, but it's a lot better than the full‑band method for most musical applications. A further refinement is that very high frequencies (above the normal sibilance range) can be switched to bypass the process. "