What is proper air amount for my two 12 cvr kickers they are in one box built for single cab truck length of bench seat 4ft by 6 inches

To calculate your enclosure's air volume in cubic feet, measure the height, width and depth of the inside space of your enclosure, in inches, and multiply.( Example: 18 inches high x 16 inches wide x 14 inches deep = 4,032 cubic inches. Next, divide this product by 1,728 (the number of cubic inches in a cubic foot). Example: 4,032 / 1,728 = 2.33 cubic feet. The air space/volume of this enclosure is 2.33 cubic feet.) this way you can build anybox needed. Hope this helps. To calculate your enclosure's air volume in cubic feet, measure the height, width and depth of the inside space of your enclosure, in inches, and multiply.( Example: 18 inches high x 16 inches wide x 14 inches deep = 4,032 cubic inches. Next, divide this product by 1,728 (the number of cubic inches in a cubic foot). Example: 4,032 / 1,728 = 2.33 cubic feet. The air space/volume of this enclosure is 2.33 cubic feet.) this way you can build anybox needed. Hope this helps.