Each system consists of a mixing console, sound processing equipment, power amplifiers, and speakers.
Without a foldback system, the sound that on-stage performers would hear from front of house would be the reverberated reflections bouncing from the rear wall of the venue.
The naturally reflected sound is delayed and distorted, which could, for example, cause the singer to sing out of time with the band.
In situations with poor or absent foldback mixes, vocalists may end up singing off-tune or out of time with the band.
An outdoor rock concert may use large racks of a number of power amplifiers to provide 10,000 or more watts.
In the smallest PA systems, the performer may set their own main and monitor sound levels with a simple powered mixing console.
Each monitor mix contains a blend of different vocal and instruments, and an amplified speaker is placed in front of the performer.
With these systems, singers could only hear their vocals by listening to the reflected sound from the audience-facing front-of-house speakers.
This was not an effective way to hear one's vocals because of the associated delay which made it hard to sing in rhythm with the band and in tune.
The use of performer-facing loudspeakers for foldback or monitoring may have been developed independently by sound engineers in different cities who were trying to resolve this problem.
The earliest recorded instance that a loudspeaker was used for foldback (monitoring) was for Judy Garland at the San Francisco Civic Auditorium on September 13, 1961; provided by McCune Sound Service.
[5] Bill Hanley working with Neil Young of Buffalo Springfield pioneered the concept of a speaker on the floor angled up at the performer with directional microphones to allow louder volumes with less feedback.
Monitor systems also helped rhythm section instrumentalists hear each other and thus improve their playing together even on a huge stage (e.g., at a stadium rock concert) with the musicians far apart.
The simplest monitor system is a speaker pointed at the performer fed from the FOH mix.
These mixes are pre-fader so that changes to the FOH levels do not significantly affect what the performers hear on stage.
The FOH mixer is operated by an audio engineer who must mix for the audience and also tend to the needs of the musicians on stage.
In addition, there may be side-fill monitors to provide sound for areas on stage not covered by the floor wedges.
With advances in digital technology, it is now possible to transmit multiple audio channels over a single Ethernet cable.
If monitor speakers are used, feedback problems are common when the performer turns their microphone up too loud.
A recent trend has been to build the amplifier and associated sound processing equipment into the monitor speaker enclosure.
A small floor monitor might use a 12" woofer with an integrated high-frequency horn or driver combination.
This is a positive feedback loop that reinforces the specific frequency, causing the speaker to howl or squeal.
The bandwidth or Q of each band can either be 1/3, 2/3 or one octave, giving a 31-band, 15-band, or 10-band for a graphic equalizer that covers the audio frequency range.
The stage mix consists of whatever vocal and instrument sources are connected to the sound reinforcement system.
While an amplified monitor speaker can also be used for this purpose, the high sound volumes in many club settings make hardshell headphones a better choice because the hard plastic shell and foam cushions help to block the room noise.
In the 2000s, some bands and singers, typically touring professionals, began using small in-ear-style headphone monitors.
This reduced on-stage volume makes it easier for the front-of-house audio engineer to get a good sound for the audience.
One drawback of in-ear monitors is that the singers and musicians cannot hear on-stage comments spoken away from a microphone (e.g., the bandleader turning away from the vocal mic and looking at the band and calling for an impromptu repetition of the chorus) or sounds from the audience.
[20] The tactile transducers are attached to the drummer's stool (throne) and the vibrations of the driver are transmitted to the body and then on to the ear in a manner similar to bone conduction.
[23] The term foldback is sometimes applied to in-ear monitoring systems, also described as artist's cue-mixes, as they are generally set up for individual performers.