HD

570 Part VIII Audio Mixing
Amplifiers and Signal Levels
Audio speakers require signals with higher voltage than consumer and professional
equipment can provide directly. Speakers require speaker level audio signals, while
audio devices such as tape recorders and audio mixers usually provide line level signals.
An audio amplifier boosts line level signals to speaker levels to properly drive speakers.
Wide gauge speaker cables that can handle the higher electrical strength of speaker
levels are used to connect the amplifier to speakers. For more information about audio
signal levels, see “Microphone, Instrument, and Line Level” on page 574.
Self-Powered Versus Passive Speakers
Speakers powered by an external amplifier are called passive speakers. When you use
separate amplifiers and passive speakers, complex factors such as impedance matching
and cable length affect the overall frequency response and quality of your audio.
Instead of using a separate amplifier and speakers, a simpler option is to use self-
powered speakers (speakers with built-in amplifiers). These have become increasingly
popular, especially for studio monitoring and video editing.
Self-powered speakers deliver more consistent performance because both components
are designed to work together and are housed in a single enclosure. For video editing
systems, self-powered speakers are a good, easy-to-use solution. Self-powered speakers
accept line level inputs, so it’s fairly easy to connect them to your audio interface.
Matching Your Mixing and Screening Environments
It’s critical that you monitor your mix in an environment that closely matches the
final viewing environment. A movie destined for a theater should be mixed on an
audio system that matches the theater sound system. Likewise, a movie destined for
DVD release for home viewing should be mixed on a system that resembles a home
viewing environment.
Setting Up a Proper Audio Monitoring Environment
Room shape and material are just as important as the quality of the speakers
themselves. Every surface in a room potentially reflects sound, and these reflections
mix together with the sound originating from the speakers. Rooms with parallel walls
can create standing waves, which are mostly low-frequency sound waves that reinforce
and cancel each other as they bounce back and forth.
Standing waves cause some frequencies to be emphasized or attenuated more than
others, depending on your listening position. When you mix in a room that creates
standing waves, you may adjust certain frequencies more than necessary. However, you
may not notice until you play back your audio in a different listening environment, in
which those frequencies may sound overbearing or nonexistent.