The original – redesigned.

The SPL DeEsser is unique – and has been since 1996. The Auto Dynamic DeEsser removes undesired sibilant frequencies in a simple and musical way, cancelling out S-sounds without affecting the natural character or timbre of the voice.

The newest generation of the DeEsser Mk2 features the same processing qualities as its predecessor, but comes in a new design and has an even better feel due to the solid aluminum knobs. The DeEsser Mk2 offers two mono DeEssers in one 19″ device. The De-Esser uses a unique technology to reduce sibiliance in a mix or on vocal tracks.
It automatically detects and hones in on the sibilant frequencies leaving neighboring
frequencies unaffected. These S‑sounds are mixed back into the main signal phase-inverted to cancel out the sibilance. The result is a sound-neutral, inconspicuous and extremely effective process.
Even at high S‑Reduction values the de-essing has an egligible effect on the character and timbre of the voice.

Get more information here: https://spl.audio/en/spl-produkt/deesser-mk2/