Check the listing for details. Custom Ported Sub Enclosure Box for 1 18" Sundown Audio SA Series SA-18 - BIRCH. Condition: New. Listed at 459.95 USD. This listing is for a custom enclosure for a Sundown Audio SA Series 18" subwoofer. We use 3" aeroports to reduce port noise so you get nothing but clean clear bass from your sub. Also, the sub is recessed 3/4" into the box. All joints are glued and screwed together. We include an internal brace to insure that the box will hold up against the high output of the subwoofer for as long as you need it to. - 3/4" Birch Plywood Construction - 1.5" Mounting Surface - Internal Brace Included - Plexiglass Window: 1/2" Thick - 14" x 12" - Port Tubes: 3" x 13.25" - Tuned to 32 Hz (adjustable by request) - Black Carpet (charcoal carpet available by request - Exterior Dimensions - - 34" Length - 16.25" Height - 22" Depth - 4.5 Cubic Ft - Net Volume - Roughly 60 lbs - 1 Terminal included - Sealed air tight with liquid nails caulk