Arturia Pure SUB is a bass design synthesizer, not a general soft synth that happens to reach low notes. It splits a bass sound into three independent layers, a clean fundamental (Sub), a shapeable harmonic layer (Harmonics, with Pressure and Reese modes), and a grit-and-movement layer (Texture, with ring/amplitude modulation, distortion, and the Corroder source), then blends them at a filter stage with more than 40 filter modes.
The instrument's signature feature is Sub Regen, which restores a clean fundamental after distortion and saturation, so the low end keeps its weight no matter how aggressive the patch. A 33-mode Sub Processor, a 12-slot FX rack with 18 effects, and a Maximiser handle the finishing, while a dedicated Pitch Envelope makes 808-style attacks quick to dial in.
Against UVI Rumble, the other notable dedicated bass synth, Pure SUB splits by sonic role rather than frequency band and costs a quarter as much at its intro price. It will not replace a broad instrument like Serum 2 for leads and pads, but for bass-led production it is a focused, affordable specialist.