Control of third octave vibrations in a mill stand can be achieved using a high-speed piezoelectric assist coupled to a hydraulic gap cylinder to increase the damping of the roll stack. Vertical movements of the roll stack (e.g., the top work roll) can be determined through observation (e.g., measurement) of hydraulic fluid pressure of the hydraulic cylinder or entry tension of the metal strip. After determining vertical movements of the roll stack, a desired change in hydraulic pressure can be determined to overcome, reduce, or prevent third octave vibration. This desired change in hydraulic pressure can be effectuated at high speeds (e.g., at or above approximately 90 hertz) using the piezoelectric assist.