Short definition
A stage monitor is a speaker placed on stage that plays back a personal mix for performers, presenters, or speakers so they can clearly hear themselves and other elements of the show.
Detailed explanation
While the main system serves the audience, the stage monitor is meant for the performers. Without adequate monitoring, artists can't track their pitch and timing, and speakers can lose their place in a script. Typical monitors are wedge-shaped and placed on the stage floor in front of the performer.
Each performer usually needs an individual mix: the singer wants their own voice and the rhythm foremost, the bassist wants kick drum and bass up front, and the host needs a clear speech return. These mixes are built separately at the monitor console or via aux sends on the FOH desk. Stage speakers are acoustically challenging since they sit within the microphones' pickup range and can trigger feedback. In-ear monitoring is increasingly used as an alternative.
Relevance in this field
Stage monitors are an often underappreciated element of event technology. Poorly set monitoring is a common cause of feedback and unhappy performers.
Practical example
At a corporate event with live vocals and a band, four wedge monitors are deployed: two for the singer and one each for guitar and keyboards. A monitor engineer builds four individual mixes on a separate digital console.
Related terms
In-ear monitoring, mixing console, sound system, FOH