Apple Final Cut Pro 6 - Manual (Page 840)

Chapter 2 Assigning Output Channels and External Audio Monitors 55
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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 Volume 1, Chapter 12, “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.
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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.