Transmission of vibrations into the cabin while driving and the general comfort of the driver is essential for agricultural and heavy-duty vehicles. Due to long working hours and rough terrain during operation, reduced attention or health problems may occur when significant vibrations are transferred from the vehicle chassis to the driver. One of the modern damping systems which can drastically minimise vibration transmission is the semi-active suspension system featuring a Magnetorheological damper. This damper can adjust the damping level using varying currents through the coil. The advantage of this system is the wide dynamic range and the fast response time of damping force. This paper aims to create a device for testing a S/A controlled fast MR damper in seat suspension, further measuring the effectiveness of the damping system in compare with passive damper.