High fidelity is the attempt to reproduce by electronic and electromechanical devices (and without distortion) the full range of audible sound from 20 Hz to 20 kHz. A reproducing system is called as “Hi-Fi”, if it fulfills the above conditions and comes as close as possible to sounding like original. In other words, the reproduced sound should be exact replica of the recorded sound.
“Fidelity” means “Faithfulness”. An ideal hi-fi system should
1.Be complete free from noise. The S/N ratio should be infinite for complete AF band. In other words, there should be no frequency distortion.
2.There should also be no amplitude or phase distortions.
3.It should be able to detect the direction for which a particular sound is coming.
4.It should create stereophonic (3 dimentional effects).
The quality of reproduction system will depend upon many factors. The acoustics of the room and deficient (poor quality) electromechanical components (microphones, speakers) will also effect output of the system. However a Hi-Fi system at the minimum should contain an input source such as record player, an audio amplifier a loud speaker more elaborate system may and contain more than one input source, separate pre-amplifier and a multiple speaker system at the output.
The reason, why people prefer higher cost of separate components instead of a radiogram in a single cabinet is the better quality of each individual component especially the amplifiers and speakers and also because of the absolute need for the speakers to be housed separately for high quality (Hi-Fi) sound reproduction.
The stereophony is made of two terms stereo + phone. Stereo means solid (3 dimensional) and phone means sound, i.e., stereophony means “3 dimensional sound”. Stereophony gives us original sound effects and we can feel its depth as well as direction. The human system of hearing is also stereophonic.
The conventional method of mono-phonic (mono means single) reproduction over a single channel cannot do faithful reproduction, as it cannot preserve the minor details of the original sound.
Stereo-phonic (Stereo means two) reproduction is based on the fact that we have two ears. If we close one ear for some tome, we can realize the importance of two ears. One ear cannot preserve the depth of sound. The stereo requires broadcasting, recording and reproduction over two separate channels to satisfy our hearing by two ears. Stereo also satisfies our “two eared three dimensional” hearing. The monophonic reproduction cannot differentiate between left and right, up and down or front and back sounds. A stereo may or may not be a hi-fi.
Actually the stereo system involves separation of low and high frequencies. Human voice has low frequency, while the musical instruments have high frequency. The system records, amplifies and reproduces them on separate channels. Each channel may have one or more speakers.