Skar Audio SDR 18's In Ported Box. This box is a CT Sounds design built to spec, 10.4cu ft air space total, tuned at 32hz. Dual 2 ohm voice coils, these speakers are wired in a series/ parallel configuration with a final impedance of 2 ohms. 2400w max power handling, 1200w RMS. This speaker/ box combination is a perfect match, the sound is low, deep, and loud. This was indoor and never abused, the loudest I ever had them was maybe a third of what they can handle and are capable of and even at that they were shaking the walls and knocking things off of shelves. They are in perfect condition.