An in-ear monitor that can be customized for particular applications and individuals includes a housing formed from a body and a cover. A dynamic driver is mounted in a cavity in the housing on an angled mounting flange. The dynamic driver is acoustically coupled to a trumpet-shaped sound collector. The trumpet-shaped sound collector is coupled to a main sound bore that exits an opening in a nozzle portion of the body that is inserted into the ear canal of a user. An ambient sound port collects ambient sound and couples it to the sound bore. An additional bass port increases the bass response of the monitor. Ear impressions are used to customize the body of the monitor to the ear of a user and the location of the bass and ambient sound ports can be altered for different applications.