Specifications

5.1-Channel Production Guidelines Production Environment
3-12
frequencies within the system. In this case, there are more options, as the five main
channels are full range and an extra LFE channel is added.
Possible combinations of speakers include five full range main speakers and a subwoofer
for the LFE; five small speakers for the main channels and a subwoofer for both the LFE
and all five main channels; and various combinations of the above examples.
As with consumer 5.1 applications, studios must be able to reproduce all reasonable
frequencies from each full bandwidth channel. Crossovers, subwoofers, and main
speakers should work together to give flat response for each of the five main
channels. In addition, larger rooms may dictate the need for more than one subwoofer
to achieve adequate bass response. Many manufacturers of near-field monitors make
complementary subwoofers to complete the system.
When utilizing the LFE channel in a mixing situation, it is important to band-limit the
information for this channel. In the Dolby Digital encoding process, the encoder will
brickwall filter the LFE signal at 120 Hz. To properly hear the LFE content, a sixth or
seventh order 120-Hz low-pass filter must be included in the monitor chain. It is
advisable to include this filter in the console output before the monitor such that both the
recorded information and the heard information are band-limited. Failure to include
this filter will result in hearing substantial bass information above 120 Hz in the mix
that will not be present in the Dolby Digital encoded version. 120 Hz is the proper
crossover frequency for theatrical film applications.
For consumer applications such as DVD and Digital TV, the consumer decoders add
a slight twist to the equation. Consumer decoders take the LFE signal and add any