Autor: Karl M. Slavik

Mixing in Stereo and Surround Sound

An exciting insight into the mixing aesthetics of the sound.

The relationship between pictures and sound in the production of high quality programming is essential. The synchronisation and expert editing of sound sources and video plays a vital role in the suspension of the disbelief that a viewer enjoys with a great programme.

The following charts provide an overview of the basic sound design and mixing for various applications. The term sound mix describes how the various sound elements relate to each other, and their level of audibility as they are played out during a programme. Despite many similarities, there are striking differences between the way that sound is mixed for cinema and TV, which need to be taken into account.

Mixing for Cinema and High-end TV

Most feature film productions, and high-end television or online commissions follow a traditional approach to cinematic sound: the dialogue is mixed entirely on the centre channel and is - regardless of the position of the actor in the picture - not panned to other speakers. This approach is used to ensure the viewer is constantly oriented to the centre of the image and therefore the action. To augment this Key-Effects, which are essential for understanding the scene, usually stay on the centre channel and are rarely carried dynamically across the surround sound set up.

General effects, atmos tracks, music and related effects (e.g. reverb) are panned on the left and right front channels and mixed as required in the surround channels. See the following figure. In line with Dolby’s best practice guides, exaggerated surround effects on pictures and action should be avoided.

TV documentaries sometimes depart from the classic centre channel-assignment of dialogue, and  provide it across the L and R channels as well, as shown in the second figure.

Classic cinema and TV Surround Sound with dialogue in the Centre channel

Mixing for Television programmes and Sports

There are three modes for the placing of dialogue in a surround mix:

Mode 1 All dialogue should be present in each of the three front channels – but this does not mean that the dialogue must be at equal level in each of the front channels. Mode 1 is generally more suited to the home listening environment. 

Mode 2 In-vision dialogue across the three front channels and out-of-vision dialogue in the centre channel only. 

Mode 3 All dialogue in the centre channel only. Mode 3 is similar to cinema mixing and as such may be the least suited to the home listening environment. 

It’s important to check the delivery specifications for the broadcaster, to ensure that the dialogue channels are correctly configured.

Sound levels need to be balanced across the surround speakers and peak levels need to be carefully measured to ensure that music and effects do not drown out the dialogue. This is a common cause of audience complaints. It’s also important to balance the dialogue across the centre and L and R speakers if you are mixing across all three front channels. 
Producers should take care with this approach to mixing, as with lots of panning your audience may not be focusing on the centre of the screen for large screen televisions.

TV Panning with dialogue and Divergence

Music, programme repeats, commercials and promotions are - if not directly available or up mixed in 5.1 - presented as stereo signals, left and right. The Surround sound, atmos, audience reaction (applause) and room responses (reverberation) are downmixed into the stereo mix by the receiver for most HD broadcasts. For some legacy SD devices, a stereo mix of the audio should be provided. It is essential that the mono and stereo down-mixes of a surround programme are monitored in at least equal measure to the surround mix. A large majority of viewers will be listening in stereo rather than 5.1 for some time to come. It is also important to be aware that the centre channel could allow viewers listening in surround to overhear off-microphone conversation not intended for broadcast during live mixes, but which may be masked when monitoring in stereo or mono.

Automated down-mixes of surround sound should always be checked on receiver equipment. Any external processor (e.g. a Dolby DP570) must be set to apply the programme’s metadata, to ensure that the down-mix is the same as viewers at home will experience. 

Sound Mixing for Music Events

Surround sound mixes for movies, sports, shows, documentaries and concert recordings of classical music are based on keeping the viewer engaged with the centre of the image, and providing a clear relationship between pictures and sound.

When working in music events, there is a different approach to sound mixing – particularly for jazz, pop and rock. In this format, the demand is for a purely artistic approach, the pictures are painting a story of the performance. Instruments are not mixed for surround sound based on what you can see on the screen – instead the sound design and mic placing for music events focusses on putting the individual in the middle of the performance.

"Abstract" Surround - the example of a jazz-rock band

The viewer listens to the performance as if they were on stage, in the middle of the band. And the pictures change to support the performance that the audience are listening to. This approach has very positive audience feedback as the music can wrap around the viewer. Example: See illustration above.

Author: Karl M. Slavik, Arte Cast Vienna

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