A speaker system in a high heel shape. The enclosure is designed as a folded acoustic transmission line ( see "https://en.wikipedia.org/wiki/Acoustic_transmission_line" for physical details) to give low frequency support. It's not like a subwoofer but quite decent. The pressure chamber behind the driver acts like a low-pass filter to reduce higher frequencies dropping out of the vent. It was made with blender and partly "handdrawn" as you can see at the different thickness in the course of the inner wall. Well, this imperfectness helps reducing housing resonances. :-)