Unless you're going for an obvious effect, our familiarity with the sound of the human voice makes over-treated vocals obvious or unpleasant to the ear. While different vocalists require treatments that are unique to their individual voice, in general, use wide octave settings and gentle amounts of boost. EQing at the following frequencies can improve the sound of a vocal performance: For fullness, adjust between 140-440Hz, for intelligibility, adjust between 1-2.5kHz, for presence adjust between 4 and 5kHz. Sibilance occurs between 6 and 10kHz. It's best to cut here. Stay tuned for additional tips for EQing vocals.