ABSTRACT
This chapter covers the principles and practice of two-channel stereophonic recording and reproduction. Two-channel stereophonic reproduction (in international standard terms ‘2-0 stereo’, meaning two front channels and no surround channels) is often called simply ‘stereo’ as it is the most common way of conveying some spatial content in sound recording and reproduction. In fact ‘stereophony’ refers to any sound system that conveys three-dimensional sound images, so it is used more generically in this book and includes surround sound. In international standards describing stereo loudspeaker configurations the nomenclature for the configuration is often in the form ‘n-m stereo’, where n is the number of front channels and m is the number of rear or side channels (the latter only being encountered in surround systems). This distinction can be helpful as it reinforces the slightly different role of the surround channels as explained in the next chapter. (Readers familiar with earlier editions of this book should note that the broadcasting nomenclature of ‘A’ and ‘B’, referring to the left and right signals of a stereo pair, has been replaced in this edition by ‘L’ and ‘R’. This is in order to avoid any possible confusion with the American tradition of referring to spaced microphone pairs as ‘AB pairs’, as contrasted with ‘XY’ for coincident microphones.)
It might reasonably be supposed that the best stereo sound system would be that which reproduced the sound signal to the ears as faithfully as possible, with all the original spatial cues intact (see Chapter 2). Possibly that should be the aim, and indeed it is the aim of the so-called ‘binaural’ techniques discussed later in the chapter, but there are many stereo techniques that rely on loudspeakers for reproduction which only manage to provide some of the spatial cues to the ears. Such techniques are compromises that have varying degrees of success, and they are necessary for the simple reason that they are reasonably straightforward from a recording point of view and result in subjectively high sound quality. The results can be reproduced in anyone’s living room and are demonstrably better than mono (single-channel reproduction). Theoretical correctness is one thing, pragmatism and getting a ‘commercial sound’ is another. The history of stereo could be characterised as being something of a compromise between the two.
