Mono
Mono or monophonic describes a system where all the audio signals are mixed together and routed through a single audio channel. Mono systems can have multiple loudspeakers, and even multiple widely separated loudspeakers. The key is that the signal contains no level and arrival time/phase information that would replicate or simulate directional cues. Common types of mono systems include single channel centre clusters, mono split cluster systems, and distributed loudspeaker systems with and without architectural delays. Mono systems can still be full-bandwidth and full-fidelity and are able to reinforce both voice and music effectively. The big advantage to mono is that everyone hears the very same signal, and, in properly designed systems, all listeners would hear the system at essentially the same sound level. This makes well-designed mono systems very well suited for speech reinforcement as they can provide excellent speech intelligibility.
Stereo
This is what many people mistake for stereo sound systems, because there are two channels and a "stereo" console is connected to the front of the system, and stereo amplifiers and equalizers are used throughout the system. What is missing from most of these systems is uniform coverage of the entire listening area, and a minimal level and phase response difference for each channel's coverage of the listening area. To achieve proper loudspeaker coverage to replicate a stereo image in a large venue, it is necessary to have a loudspeaker system for each channel that can provide uniform coverage of the entire listening area while maintaining the directional cues. This is a very expensive, and sometimes impossible proposition.
Two channel systems usually suffer from having half the people in the listening area only hear half the audio program, which makes two channel systems a poor choice for music reinforcement. A large portion of the listeners hear a completely different music mix from other listeners. This is an all-too-common oversight in venues that are intended for music and entertainment, even high profile venues where they deserve better system designs. It tends to be a common misconception brought forward by people with a background in portable or live sound systems.
When a two channel system is used to reinforce a mono voice microphone, the seats either side of the room centreline, exactly between the two loudspeakers, also experience substantial variations in frequency response and uniformity of coverage due to interference and signal cancellation when identical signals arrive from the two channels at different times. This makes two channel systems especially ineffectual for speech reinforcement
Left/Centre/Right
There are specialized applications for sound systems described as Left/Centre/Right configurations. This must combine the best of both worlds, right? Well it can, but the loudspeaker system must also be designed to the highest common denominator not the lowest. It is also important with an LCR system that the mix engineer understand which signals must be routed to which loudspeakers, and which signal routings will create problems. LCR systems also are not suitable for use in all room shapes and configurations.
LCR systems are common in drama theatres and large churches where there is a requirement for both mono speech reinforcement and music or sound effects cues to be localized or mixed with a particular perspective, with a stereo or stereo-like imaging. The three loudspeaker systems must each provide coverage of the entire seating area while maintaining level and directional cues, just like the mono and stereo systems described above. There are some clever "cheats" a system designer can use to achieve the extended listening area for stereo coverage, and that invloves using "stingers" or infill loudspeakers.
Which one's the best? Mono or Stereo
As with many questions about sound systems, there is no one right answer. A well designed mono system will satisfy more people than a poorly designed or implemented two channel sound system. The important thing to keep in mind is that the best loudspeaker design for any facility is the one that will work effectively within the, programmatic, architectural and acoustical constraints of the room, and that means (to paraphrase the Rolling Stones) "You can't always get the system that you want, but you find some times that you get the system that you need." If the facility design (or budget) won't support an effective stereo playback or reinforcement system, then it is important that the sound system be designed to be as effective as possible, even if that means giving up a desirable program requirement like stereo.
2.0
It is same as the stereo that above mentioned
2.1
It is same as the stereo that above mentioned but having a difference. In 2.0 have only two channels (Left&Right),But in 2.1 three channels are there as output left,right and LFE(Low Frequency Effect) channel.Only low frequency signals are routed to LFE channel.It is connected to Sub Woofer for Bass effect. This low frequency channels are derived from the left and right channels
Multi channel audio
Multi channel audio have more than three channels
4.0
Quadraphonic sound (4.0 stereo): Although multi-channel sound had been experimented with both for audio and in movies since at least the 1930s, it wasn't until 1969 that technology and the audio industry were ready to commercialize it. At the Audio Engineering Society meeting in 1969 Vanguard records demonstrated discrete four-channel sound on a four-channel reel to reel deck. Heads turned, production geared up and the first home quad recordings on open reel tape were released in 1970. ["Quad" Bob]
Discrete reproduction is the only real quadraphonic system. As its name suggests, with discrete formats the original four audio channels are passed through a four-channel transmission medium, presented to a four-channel reproduction system, and fed to four speakers. This is defined as a 4-4-4 system.
The CD-4 encoding/decoding matrix:
(LF+LB)+(LF-LB)=2LF or Left Front
(LF+LB)-(LF-LB)=2LB or Left Back
(RF+RB)+(RF-RB)=2RF or Right Front
(RF+RB)-(RF-RB)=2RB or Right Back
Basic SQ Encoding Matrix Left Front Right Front Left Back Right Back
Left Total 1.0 0.0 -j0.7 0.7
Right Total 0.0 1.0 -0.7 j0.7
j = + 90° phase-shift
To provide mono-compatibility a variation on this matrix was proposed:
Modified SQ Encoding Matrix Left Front Right Front Left Back Right Back
Left Total 1.0 0.0 0.7 -j0.7
Right Total 0.0 1.0 -j0.7 0.7
j = + 90° phase-shift
