Accommodating stereo playback – Apple Compressor 3 User Manual
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In most music productions (with such exceptions as the famous cannon shots in
Tchaikovsky’s “1812 Overture”), the LFE channel is not necessary. The LFE signal is also
discarded in the Dolby Digital Professional downmix process, so intense bass signals do
not stress small stereo systems. Be sure not to include vital information in the LFE channel
that would be missed in mono, stereo, or Pro Logic playback.
Because LFE is separate from other channels, its ability to blend with higher frequencies
can be affected by filters used to generate the LFE signal. To ensure a cohesive audio
signal, keep the entire signal together in the main channel or channels.
Avoid creating an LFE channel for material originally produced without one. Dolby Digital
Professional’s five main channels are all full-range, and the LFE channel does not increase
the frequency response. Dolby Digital Professional decoders offer bass management,
directing low frequencies to a subwoofer or other suitable speakers. An LFE track may
interfere with bass management.
Accommodating Stereo Playback
Even with the popularity of 5.1 systems, you should always address stereo reproduction.
There are three basic ways to do this:
• Prepare a new stereo mix from the original multitrack elements (using conventional
stereo-mixing sessions).
• Prepare a studio-adjusted downmix from the multichannel mix. This method takes
advantage of the work that has gone into mixing the 5.1 version. It retains flexibility in
the exact proportions of each channel represented in the final stereo mix.
• Let the decoder derive a stereo downmix, based on preset formulas in the decoder.
Downmix options and dynamic range control effects can be previewed and adjusted
in the production studio, and a range of adjustments is possible.
Always check the mix on an inexpensive surround system to evaluate how well it sounds
on modest playback systems.
Note: For more information about Dolby Digital Professional, see “Frequently Asked
Questions about Dolby Digital Professional,” available at the Dolby Laboratories Inc.
website at
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Chapter 10
Creating Dolby Digital Professional Output Files