A stepped enclosure for a rotating disc data storage device having an actuator operably moveable within a range of movement adjacent the rotating disc in a data reading and writing relationship. The stepped enclosure comprises an airflow conditioning surface disposed in a substantially close-fitting relationship with the disc and spatially disposed therefrom a first distance. The enclosure further comprises a niche, or recessed area, in the airflow conditioning surface apart from the actuator range of movement defined by a recessed surface disposed a second distance from the disc greater than the first distance.