The π cornerhorn covers the entire audio band. It uses the expansion of a room from the apex of the corner as a large horn, and this expansion forms the horn in toto. The chamber between the driver and the corner forms the horn's front chamber and the speaker box forms the horn's rear chamber. You can set compression ratio with a compression plate/ring too. And you can vent the rear chamber to extend bass response. It's a very simple and effective configuration. See the posts called "Cornerhorns" and "Room corner charatcteristics" for more discussions along these lines.