7
AVOIDING FEEDBACK
Feedback (the shriek sometimes emitted by sound systems) occurs when the microphone (or pickup) and speaker are po-
sitioned too close together for a given level of volume. Once feedback occurs it will continue until either the volume is de-
creased or the distance between the microphone and speaker is increased.
Gain is the degree to which the volume may
be increased before feedback begins. In setting up a sound system, the object is to maximize the gain while maintaining
sufficent coverage of the audience.
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In most cases, the (main) speakers should be placed on stands, at a height slightly above the heads of the
audience, in front and to each side of the stage.
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They should be rotated inward, but only slightly. More than a few degrees of rotation can reduce the gain.
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Powering monitor speakers with the same channel of the amplifier used to power main speakers may cause
feedback.
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Ideally, monitor speakers should either have their own volume controls or be routed through a separate channel of the
amplifier so the volume of one speaker system can be adjusted without affecting the other.
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The X250’s mixer provides separate controls for the mains and monitors. Separate monitor outputs make it possible
to tailor the monitor mix and the levels, independent from the mains, when AUX RETURN is used for a monitor mix.
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The X250’s tone controls provide one means of controlling feedback. Begin with the MID and HIGH controls set at 12
o’clock, and LOW at 10 o’clock. Gradually increase the volume until it reaches the point immediately before feedback
(the speaker should ring slightly). Turn the MID control to 10 o’clock. If the ringing stops, leave the MID control in that
position. If the ringing persists, return the MID control to 12 o’clock. Turn the HIGH control to 10 o’clock. If the ringing
stops, leave the HIGH control in that position. If it persists, return the HIGH control to 12 o’clock and repeat the pro
cess, turning the MID and HIGH controls to 9 o’clock and the LOW control to 7 o’clock. Periodically talk through the
system, while repeating this process, until several notes ringing at once or sound quality is noticeably reduced.
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In high volume applications, reduce all the LOW frequencies.
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The X250 automatically provides a flat frequency response whenever the tone controls are set to their
center-detent positions.
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Use a
unidirectional microphone. Since there are many brands, with wide variance in their amounts of rejection (the
ability to
not pick up peripheral sounds), experimentation provides the best means of choosing the right microphone.
MONITOR PLACEMENT
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We recommend Galaxy Audio’s HOT SPOT Personal Monitor. Its controlled bandwidth (optimized for vocals) pro-
vides superior intelligibility and gain before feedback.
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The HOT SPOT should be positioned within arm’s reach of the performer. The closer it is, the louder it is.
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The HOT SPOT should be placed to the rear of the microphone being used by the performer.
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If, in a system with multiple monitors, one monitor is substantially nearer a vocal microphone than are the other
monitors in the system, its volume may need to be reduced to avoid limiting the gain of the entire monitor system.
LOW FREQUENCY DISTORTION
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If the speaker begins to distort, adjust the LOW tone control.
SOUND REINFORCEMENT BASICS
SOUND REINFORCEMENT BASICS
SOUND REINFORCEMENT BASICS
SOUND REINFORCEMENT BASICS
SOUND REINFORCEMENT BASICS