Foldback

During a live music performance, the sound performers hear from the rear-facing loudspeakers on stage is referred to as the foldback mix. This may be produced on the same physical console as the main mix for the audience (called the 'front of house' mix), or may have a dedicated engineer and console on stage.

Foldback is essential to performers as the sound they hear from front of house will reverberate; most of what they hear will be reflected from the rear wall of the venue and will therfore be delayed and distorted.

Artists need to hear a mix that is dry (i.e. without electronic effects / acoustic reverb etc.) and projected directly to them if they're to stay in time and in tune with each other; the most obvious symptom of a poor or absent foldback mix is vocalists singing off-tune.

The term foldback is also less correctly applied to 'in-ear monitoring' systems – these are better described as a 'artist's cue-mixes' as they're generally set up for individual performers.

In power supply design, foldback is a function whereby a constant voltage power supply's output voltage is reduced under overload conditions, either to maintain either a constant current into a load, or to ensure that the supply's output devices remain within their safe operating areas (SOA).

Usually both restrictions are enforced; constant current first (this is often a 'feature' and is adjustable) which is overridden by SOA protection should the overload become more severe. In general, any power supply whose voltage falls linearly as load increases past a preset overload threshold is said to have foldback.

The term may also (though less commonly) be applied to similar protection in audio power amplifiers.