Stereophonic recording equipment

The normal individual has no more than two ears (unfortunately, sometimes only one, putting him at a stereophonic disadvantage), and so it w a s at first erroneously believed that only two channels need be used for stereophonic reproduction. Earphone listening, binaurally, has certain deficiencies, except for certain subjective listening studies. Loud-speaker reproduction reaches more people at a given time, and corrects some of the deficiencies of listening through earphones. However, room acoustics problems, not present when earphones are used, enter here. An optimum minimum of three channels for loudspeaker listening h a s been established by comparative listening tests. Electrical phasing, time phasing, and balanced loudness between channels are necessary for the maximum realization of the benefits of a stereophonic system. Minimum harmonic and intermodulation distortion obviously aids any system. Transmitted band width has an effect on realism also.