MusicTechHelpGuy breaks down the knee control in Logic Pro's compressor, the setting that shapes how compression kicks in around the threshold.
A hard knee creates an abrupt switch from uncompressed to compressed, treating everything past the threshold the same. A soft knee eases in gradually, so signals just above threshold get compressed lighter than signals well above it.
His rule of thumb: hard knee suits precise, individual drum tracks like kick, snare, and toms. Soft knee tends to work better for vocals and acoustic instruments where a more natural dynamic feel matters.
He demos both settings on a kick drum, showing how a hard knee compresses every hit evenly, while a soft knee leaves softer hits mostly untouched and clamps down harder only on the loud ones.