A phase plug having an input face circumscribed by a round profile and an output face circumscribed by a non-round profile, is described. The phase plug may include several arms radiating from a central axis and separated by radial channels extending axially from the input face to the output face. Planes containing the round profile and the non-round profile may be nonparallel, and sound ports at the output face may be asymmetrically disposed about a midline of the output face. Other embodiments are also described and claimed.