What is 5.1 surround sound?
5.1 surround sound is the new audio format of the future as far as Classical music is concerned. It adds an extra dimension to the reproduction of music in the home. Rather than have just 2 speakers in front of the listener for stereo, 5.1 has
6 - that's not a mistake! 5.1 adds a center speaker in between the normal left and right speakers for stereo,
and two rear speakers (left rear and right rear) either behind or to the side of the listener, depending on room layout (see illustration
below). A subwoofer, aka the LFE (low frequency effects) channel, handles deep bass should it be required. This is the .1 of 5.1.
However, for music as opposed to a film soundtrack, a separate subwoofer channel is not necessary,
as it's mainly used for cinematic special effects. The advantage
of 5 small speakers plus subwoofer is greater domestic acceptability as the
subwoofer can be hidden away out of sight.
Why do we need 5.1? What's wrong with good old fashioned stereo? One of the fundamental limitations of
stereo is that all the reverberation of the original
acoustic space, whether recorded naturally or added artificially afterwards, comes out of the speakers from the front, together with the music. In real life, reverberation comes from all directions (unless you're in the open air!) and this limits how realistic stereo can ever be. 5.1, with its extra rear channels placed behind the listener, can re-create the original acoustic space more accurately than stereo ever can.
5.1 is a film format, i.e. it was developed for the cinema rather than for music. This is why it is frontal dominated, i.e. 3 speakers at the front and only 2 at the back, as opposed to say, 2 speakers at the front and 2 at the back. However, listening to music at a concert is also frontally dominant, so there's nothing wrong there. In the cinema, the front center channel is popularly known as the 'dialogue channel', which helps to fix dialogue to the screen. There is a multi channel format (developed in the U.K.) specifically designed for music, called Ambisonics. Ambisonics was developed decades ago and requires the use of a special microphone, called the Soundfield microphone. It also allows multiple speaker positions in the home; you can have 4 or 14 (!) as the decoder is versatile and the result is very good indeed. Unfortunately, Ambisonics flopped commercially for a variety of reasons, perhaps the main one being that it coincided with quadraphonics which also flopped commercially but was a very different and inferior kettle of fish. The recent explosion of interest in Home Cinema, first with Dolby Surround (a matrixed predecessor of 5.1 which fitted onto 2 channels) and now with discreet 5.1 (aka Dolby Digital), established the idea of multi channel sound in the home in a way that Classical music, now even more of a minority interest than before, could not. Therefore, Classical music has to use 5.1 to survive.
5.1 audio is already available on DVD (Digital Versatile Disc) video discs (with or without the picture), but the sound quality is slightly inferior to CD because it is in a data reduced format (Dolby Digital), but the public appear to be quite satisfied with the quality. Two new formats have now arrived, DVD-A (the audio only version of DVD with better quality and versatility than DVD video disks) and SACD (Super Audio Compact Disc). Both new formats will be backwardly compatible, i.e. they will still play your existing collection of CD's. Indeed, SACD has two separate layers, one with high quality multi channel sound and the other with ordinary CD stereo sound. So you will be able to play SACD's on your existing CD player and even in the car, but only the 2 channel stereo version. A 5.1 version is on the cards. You will need a new player to play the new formats as they cannot be played on current CD or DVD video players. These new formats are expected to replace Compact Disc in time. It is unfortunate that the industry cannot get its act together and decide on just one format to present to the public (as some wag said "The great thing about standards is that there are so many to choose from"). We could well see a repetition of VHS vs Betamax and DCC vs Minidisc. However, it is not technically impossible to have a player that will play both formats and this is indeed what has now happened. You would think that the mighty corporations involved would have learnt from history by now, as the history of audio is littered with failed formats. Obviously, their greed for profit is greater than their commonsense. Time will tell. One good thing is that DVD-A disks have their content duplicated in Dolby Digital 5.1 so that they can be played on the 5 odd million DVD video players that have been sold since the launch of the format. This is a very wise move indeed, as alienating 5 million customers who bought DVD video only players could well prove to be commercial suicide for DVD-A.
For those worried about the domineering effect of 6 speakers in one room, fear not! Although
today's speakers are still relatively bulky (due to most of them being box shaped), flat panel speakers that you can hang on the wall are already
here (together with televisions that you can hang on the wall). The quality is apparently not too good at the moment, but this
probably won't last. With time and development, they will probably sound as good as conventional speakers do today and they've had much time and development over the years! Also, because bass frequencies are largely non-directional, the subwoofer can be hidden away (at a pinch)
just about anywhere in a room.