What would be the best way to fire a 12" subwoofer in a 2004 Toyota Tundra 4-door

[Hayden Walker]

truck? Up, Down, or Forward? The Subwoofer is a 12" Kicker Solo Classic. I will be putting it in a sealed enclosure on top of the middle seat because there is not enough room under or below the seat for a 12" sub in my truck.