What does bandwidth mean?
Bandwidth is the frequency at which the actual oscillation amplitude is attenuated by -3dB from the commanded oscillation amplitude. This is approximately equal to the frequency at which the actual oscillation amplitude attenuates by 30% from the commanded oscillation amplitude. The bandwidth has to be tested with small driving signal, which guarantees that the attenuation of the actual oscillation amplitude is caused by bandwidth limitation, not by driving current limitation.
As an example: when a stage is driven to oscillate with a 1µm amplitude at 1Hz it will respond by oscillating at 1Hz with a 1µm amplitude. If its bandwidth is 80Hz, when it is driven with an 80Hz signal it will respond by oscillating with an amplitude of 0.7µm.