Shure DP11EQ - Manual (Page 22)

21 English –
DELAY
There are some potential problems with the arrival of sound in systems utilizing multiple
loudspeakers. The DP11EQ Delay is designed to solve two of these problems: remote speaker
alignment and phase cancellation.
Delay for Solving Remote Speaker Alignment Problems
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A
B
AMPLIFIER
AMPLIFIER
AMPLIFIER
AMPLIFIER
MIXER
MIXER
DP11EQ
WITH DELAY
Problem: Illustration A — Some larger sound systems may utilize loudspeaker fill systems. One
loudspeaker may not be enough for a large hall because of power limitations, so a fill loudspeaker
may be placed farther in front of the main speaker to augment the sound from the main loudspeaker.
This may cause the sound from the fill loudspeaker to arrive at the listener earlier than that from the
main loudspeaker. To the audience, it will seem like the sound is coming from the wrong place when
the sound from the fill loudspeaker arrives first.
Solution: Illustration B — The delay in the DP11EQ can be used to solve this problem. Place a
DP11EQ along the audio path to the amplifier of the fill loudspeaker, then set it to the proper amount of
delay. The DP11EQ with Delay will hold that audio signal in memory, releasing it to the fill loudspeaker
only when it is in time with the sound from the main loudspeaker, so the sound from both loudspeakers
will arrive at the audience at the same time. Now, the audience will perceive the sound coming from
the correct place.
Delay for Solving Phase Cancellation Problems
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A
B
AMPLIFIER
AMPLIFIER
AMPLIFIER
AMPLIFIER
MIXER
MIXER
DP11EQ
WITH DELAY
Problem: Illustration A — Phase cancellation can occur when two loudspeakers are near each
other but not precisely time aligned. The two speakers can be seen in the illustration above. The
waves represent the sound coming from each. The sound waves coming from the main and remote
loudspeakers are out of phase. Because they are out of phase, the sounds interfere with each other,
degrading audio quality. The illustration above shows how sound waves cross, causing phase
cancellations.
Solution: Illustration B — The DP11EQ Delay can be used to stall the signal to loudspeaker B
just long enough so that when it does come out, it is in phase with the sound from the loudspeaker A.
When in phase, the waves reinforce each other to maintain audio quality. Illustration B shows how the
DP11EQ delay works in a sound system.