Min Rec Sealed Box Volume (CU. FT., Liters) .66, 18.7
Max Rec Sealed Box Volume (CU. FT., Liters) 1.0, 28.3
Min Rec Vented Box Volume (CU. Ft., Liters)** 1.25, 35.4
Max Rec Vented Box Volume (CU. Ft., Liters)** 2.25, 63.8
consider how much space you have before adding more subs, more isnt better if its not in the correct enclosure.