A first and a second bale speed sensor are provided in a segment of the baling chamber of an agricultural baler. The first sensor is positioned at an upper part, while the second sensor is positioned at a lower part of the baling chamber. Respective outputs of said bale speed sensors being operationally connected to a controller which is adapted to adjust based on said outputs a synchronization between the periodically forming and pushing of a slice of crop material and the reciprocal movement of the plunger.