FabFilter Pro-DS does one thing, and it does it better than almost anything else: it removes harsh sibilance without hollowing out the vocal underneath. Sibilance is the piercing "s," "sh," and "t" energy that turns an otherwise polished take into something fatiguing on headphones. Pro-DS attacks it with the same design philosophy that made Pro-Q famous, an interactive display where you can see exactly what the plugin is catching and hear it in real time.
It excels at intelligibility. The two detection modes cover the two situations that actually come up in a mix. Single Vocal locks onto a lead take and reacts to its specific sibilant frequencies, while Allround handles busier material, full mixes, or dialogue where the source is less predictable. In Split Band mode the plugin only ducks the sibilant frequency range and leaves the rest of the signal untouched, so a bright vocal stays bright between the essing. The linear-phase processing, optional look-ahead, and up to 4x oversampling mean it stays clean even under aggressive settings.
The trade-off is value. At $199, Pro-DS costs as much as many full channel strips, and it is a single-purpose tool. Most producers already own a de-esser inside their DAW or compressor bundle, and for occasional cleanup those are perfectly adequate. Pro-DS earns its price only for people who de-ess constantly and want it to be fast and invisible. There is also just one band of detection, so unusually complex sibilance across two distinct frequency zones can require a second instance.
Against its alternatives it plays a different game. Timeless 3 is a delay, and Neutron 5 and VocalSynth 2 are broad multi-effect suites, none are dedicated de-essers, so Pro-DS wins on focus and transparency while they win on breadth. Choose Pro-DS if precise, repeatable sibilance control is a daily part of your workflow and you value the clearest interface on the market.