IF ports, front ports only to retain directionality of bass and those bass note's overtones.
IF subwoofers, a small stereo pair, same reason, and sub self powered, wired so that the bass chores are eliminated from both the main amp and main speakers
IF subwoofers, a small stereo pair, same reason, and sub self powered, wired so that the bass chores are eliminated from both the main amp and main speakers