you're missing another 416 in each enclosure. Altec had a design that used 2 416s in a box about the same dimensions. Room gain can be your friend. Your journey will be something to enjoy. Sorry to mention it again, but if you look here altec scan | Flickr - Photo Sharing!

you might get another inspitation. who knows. weed through the photos, you'll see more relating pics, even a bar graph frequency sweep.