Glazing units including a cartridge cavity outside of a seal that is located between the first and second panes to form a closed interior volume within the glazing unit are described herein, along with sashes, panels, window assemblies, and/or doors that may incorporate the glazing units. A control unit provided in a cartridge housing located in the cartridge cavity may be operably connected to one or more connected devices to provide any number of a variety of functions such as, e.g., sound control/production, optical effects, thermal effects, etc.