You need more information to calculate flow rate. Qes is the electrical Q of the speaker and only takes the electrical properties into consideration. To use the calculator enter your air velocity or volume air flow and duct areatype select your units click calculate air flow and your converted velocity and volume units will be shown.
Measure the width height and length of the carton and multiply them.
Q m c D T. CBM calculation is very simple to calculate. Calculate internal air space available for your woofers. Stiff speakers have lower Vas and tend to use small enclosures.