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Surround Sound by Steve Parr
email: steveparr@hearnoevil.net
article reproduced by kind permission of the author
Steve ParrSteve Parr is a musician, composer, engineer & producer who is well known as one of the foremost exponents of 5.1 mixing in Europe. Over the last three years he has mixed dozens of film soundtracks in 5.1 as well as writing on technical issues for the audio press, speaking at seminars and acting as an industry consultant on surround sound. He has been vice chair of the Music Producers Guild since 2001. Steve runs the Hear No Evil recording studio with Sharon Rose

5.1 FOR FILM COMPOSERS

5.1 FOR PRODUCERS

SURROUND FOR ENGINEERS-THE MAGIC PENTAGON

 
5.1 FOR FILM COMPOSERS

                     Dolby Stereo is an analogue matrixing system where the 4 signals for left, centre, right and mono surrounds are collapsed into a stereo pair by means of their phase relationships. On playback, the stereo is decoded back into the 4 signals to derive the surround sound audio picture.However, this is an imperfect system because there is a natural tendency  for the left and right signals to collapse into the centre unless they are very different; it is also difficult to control the placement of the instruments once the music is combined with the effects and dialogue.

                     Dolby Digital, also known as SRD, is a process where the sound for the film is mixed into 6 separate channels: left, centre, right (LCR), stereo  surrounds (Ls, Rs), and a low frequency enhancement channel (LFE) or sub bass. This is what is commonly referred to as 5.1, with the .1 being the LFE channel. These signals are then encoded digitally by means of a data compression process called AC3. The fundamental difference from Dolby Stereo is that once a signal source is placed in the surround spectrum during mixing, it will remain there when it is decoded.

                     As a composer, you will want to hear your music in the best possible light, so it is in your interests to deliver it to the dub as six discrete channels so that it will literally 'fill' the space of the theatre. If you mix your music in a studio properly equipped with a 5.1 panning and monitoring system, it can be dubbed far more effectively and will have more audio 'room'. It will not get swamped by effects such as gravel, rain and helicopters.

                     Music mixing consoles have a limited capability of mixing in 5.1 by routing individual signals to their various output busses: for instance, the main stereo buss could take care of the left and right, busses 1 and 2 the stereo surround, bus 3 the centre and 4 the LFE. If you want to pan a signal from the front to the back, or even place a sound in a specific spot in the room, you then have a major problem unless the console has the facility to pan between all the busses simultaneously as you can with a joystick. In our experience it is far better to distribute the mix about the room to get an ambient spread than to specifically place a sound in just one speaker.  This has the effect of making you aware of the placement of the speaker, and not the placement of the sound. This can be far distracting for the listener and can actually detract from the soundtrack as a whole.

                     As well as recording soundtracks at Hear No Evil, we receive many     recordings from elsewhere that are brought specifically to us for mixing. Very few analogue desks have the capability to mix in 5.1 unless they have either been designed specially for film. We are fortunate at Hear No Evil in that we have an Euphonix, an analogue console under full digital control. We are even capable of mixing in 5.1, and stereo simultaneously,   together with full automation of all console functions including dynamic surround panning on all faders.


                     DVD has already taken a grip throughout the world.. The format incorporates 5.1 audio together with the facility to play back the music track without the dialogue and effects tracks. Music mixed in 5.1 can and should take full advantage of this exciting new medium. The DVD Audio format has the capability of 96k/24 bit multichannel audio; even more reason to have a 5.1 version of your music.

                     For those of you who wish to know more about surround sound, you should take a look at an American publication called Surround Sound Professional, http//:www.surroundpro.com.
© Steve Parr
 
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