The engineers working on the sound-on-disc system were able to draw on expertise that Western Electric already had in electrical disc recording and were thus able to make faster initial progress. The main change required was to increase the playing time of the disc so that it could match that of a standard reel of 35 mm film. The chosen design used a disc nearly 16 inches (about 40 cm) in diameter rotating at 33 1/3 rpm. This could play for 11 minutes, the running time of 1000 ft of film at 90 ft/min (24 frames/s). Because of the larger diameter the minimum groove velocity of 70 ft/min (14 inches or 356 mm/s) was only slightly less than that of a standard 10-inch 78 rpm commercial disc.