An example of the recommended rectangular dimensions for a JL Audio 12-inch subwoofer are 18 inches by 13 inches by 13.75 inches, using .75 inch thick fiberboard. Sealed or Ported. Sealed subwoofer enclosures are completely sealed, air-tight speaker boxes. These boxes are appropriate for speakers that have a suitability factor of 50 or less. Description. Skar Audio engineered this custom, vehicle specific, dual 12-inch, sealed subwoofer enclosure specifically to fit under the rear cab seat of 2007-2013 Chevy Silverado/GMC Sierra Extended Cab trucks. Unmatched by anything else on the market today, this subwoofer enclosure was engineered from the ground up by our master craftsman to Single Sealed 12" Enclosure. Internal box volume: 1.5 cubic ft. High Quality 3/4" MDF Construction. Durable black carpeting. Pre-lined with Poly-Fil. Seams are fully caulked for better efficiency. Gold post terminals for clean and easy wiring access. Box Dimensions: 16"L x 17"D x 13-1/2"H. 30 Day return policy. For 10 inch subs mounting depth = 7.5 inches with a 7 inch magnet; For 12 inch subs mounting depth = 7 inches with a 7 inch magnet; Two speaker terminals included. Two holes cutout for the terminals. (terminals shipped uninstalled and located inside the sub box.) NOTE: Boxes are carpeted in charcoal. This subwoofer box installs in minutes and is engineered to fit the 2001 -2003 F150 Supercrew cab. We use high quality MDF and precision manufacturing in all of our Subwoofer enclosures. Features: Fits 8, 10 or 12 inch subwoofers; MDF construction ; Subs fire down ; No seat modification needed ; Rear seat will fold forward, but not flat Subwoofer Box Carbon Audio 3000W 12. Net Internal Volume: 3.9 ft 3 . Pipe Inner Diameter: 152.4 mm Tuning Frequency: 35 Hz. 12 inch subwoofer box designs and plans. We picked up the most popular 12 inch subwoofer ported box plans and sealed box plans for you. As for its dimensions, this subwoofer box is rated for 15.25 inch x 13 inch x 12 inch making it fairly compact. Although, its build quality is a bit average despite having a 1-year warranty. Best Features: 18 inch subwoofer box design Sundown Audio Dual 18's, ported box plan, 3D model. Net internal volume 12.00 cubic feet, port area 112.00 square inches, tuning frequency 30 Hz. Subwoofer box calculator online Mfq7.