Apple Final Cut Pro 7 - Manual (Page 862)

Self-Powered Versus Passive Speakers
Speakers powered by an external amplifier are called passive speakers. When you use
separate amplifiers and passive speakers, a number of factors 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.
Amplifiers and Signal Levels for Unpowered Speakers
Unpowered speakers require signals with higher voltage than consumer and professional
equipment can provide directly. These levels are known as 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
“Connecting Professional Video and Audio Equipment.”
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.
Tip: A much cheaper alternative to building new walls is to mount “bass traps” to the
existing walls. Bass traps help to eliminate parallel surfaces in the room and absorb
low-frequency energy.
If the material in a room is very reflective, the room sounds “brighter” because high
frequencies are easily reflected. Mounting absorbing material (such as acoustic foam) on
the walls can reduce the brightness of a room. A “dead room” is one that has very little
reflection (or reverberation ). Try to cover any reflective surfaces in your monitoring
environment.
862 Chapter 53 Assigning Output Channels and External Audio Monitors