This is the beginning of bass for my point source horns. The driver is an Eminence Magnum 18LF, an 18" pro woofer. It could work well in a 110L vented box but in my particular room a 60L sealed box is a good choice because the bottom end will be handled by subs. In this situation a vented alignment gains little except a bigger box.
The design is a simple sealed box with bracing and a shape which fits closer to the corners.
MDF has been cut and I've started to put together the bracing.