An optical playback or recording device is equipped with mass-unbalance detection means (20) for detecting unbalance on the record carrier (2). Mass-unbalance causes vibration and sound in the optical device when the record carrier (2) is rotated at a relatively high speed. When mass-unbalance is detected, the speed may be reduced to reduce the vibration and sound in the optical device. The mass-unbalance detection means (20) performs the following steps to detect mass-unbalance: a) determining the maximum value Umax1 of the actuator control signal (AS) at a rotational speed Ω1; b) determining the maximum value Umax2 of the actuator control signal (AS) at a rotational speed Ω2; c) comparing Formula (I) with Formula (II). If these values are substantially equal, then the effect of mass-unbalance is small, otherwise the effect of mass-unbalance is too great and the speed may have to be reduced U max ⁢ ⁢ 1 ω 1 2 ⁢ ⁢ with ⁢ ⁢ U max ⁢ ⁢ 2 ω 2 2 . ( I )