Crown Audio SASS User Manual
© 2000 Crown International, All rights
®
reserved PZM
DIFFEROID
, PCC®, SASS® and
®,
are registered trademarks of
Crown International, Inc. Also exported
as Amcron
®
127018-1
6/00
Crown International, Inc
P.O. Box 1000, Elkhart, Indiana 46515-1000
(219) 294-8200 Fax (219) 294-8329
www.crownaudio.com
SECTION ONE
Microphone Technique Basics 3
How to:
Reduce feedback and reverberation 3
Reduce background noise and leakage 4
Pick up sound at a distance 4
Reduce phase cancellations between two mics 5
Reduce phase cancellations from surface reflections 5
Reduce handling noise 5
Reduce proximity effect 5
Reduce pop 5
Achieve a natural tone quality 6
Achieve a bright tone quality 6
Achieve a good balance 6
SECTION TWO
Notes on Crown Mic Models
CM-200A 6
CM-310A 6
CM-311A 6
CM-312A 6
CM-30 / CM-31 6
CM-700 6
CM-150 7
GLM-100 7
GLM-200 7
LM-201, LM-300A, LM-300AL, LM-301A 7
SECTION THREE
Specific Applications 7
SECTION FOUR
Choosing the Right Crown Microphone 14
Condenser or dynamic 14
Boundary or free-field 14
Polar pattern 14
Frequency response 14
Application chart 15
INTRODUCTION
In this guide you’ll find suggestions on using
Crown microphones effectively. The CM, GLM, and
LM microphone lines are covered in this booklet. For
application notes on the PZM®, PCC® and SASS®,
please see the Crown Boundary Mic Application Guide.
You will find that Crown microphones can solve many
of your audio problems.
MICROPHONE
TECHNIQUE BASICS
How to reduce feedback
Feedback is a squealing sound from sound-reinforcement speakers that occurs when volume is too high.
To reduce feedback:
• Turn down the volume on the offending
microphone until feedback stops.
• Use as few microphones as possible. Gain-beforefeedback decreases 3 dB each time the number of
open mics doubles.
• Place the mic close to the sound source. The closer
the mic, the higher the gain-before-feedback. If close
miking causes an unnatural tone quality, try using
EQ to compensate.
• Equalize the sound system with a 1/3 octave graphic
equalizer. Notch out frequencies that feedback.
• Place speakers as far from the mic as possible.
• Place the mics behind or to the outside of the house
P.A. speakers. The house speakers should not aim at
the microphones.
• Use directional mics. Hypercardioid and supercardioid patterns reject feedback better than cardioids,
and cardioids reject feedback better than omnidirectional patterns.
• Use differential (noise-cancelling) mics, such as the
Crown CM-310A or CM-311A. They have the
highest gain before feedback of any mic you can buy.
The following table tells how many dB of feedback
rejection you can expect from various polar patterns,
in a reverberant sound field, compared to an omnidirectional pattern at the same distance:
Omnidirectional 0.0 dB
Cardioid -4.8 dB
Bidirectional -4.8 dB
Supercardioid -5.7 dB
Hypercardioid -6.0 dB
For example, a cardioid mic provides 4.8 dB more
gain-before-feedback than an omni mic at the same
distance from the sound source.
You can place a directional mic farther from its source
than an omnidirectional mic in a reverberant sound
field and have the same gain-before-feedback. The
table below shows the distance multiplier for each
pattern:
Omnidirectional 1.0
Cardioid 1.7
Bidirectional 1.7
Supercardioid 1.9
Hypercardioid 2.0
For example, if an omni mic is one foot from a sound
source, a supercardioid mic can be placed 1.9 feet and
have the same gain-before-feedback as the omni.
The figures above apply only when the mics are in a
reverberant sound field - say, when the P.A. speakers
are distant from the mics and the sound system is set
up indoors.
How to reduce reverberation
Reverberation is sometimes loosely called “room
acoustics” or “ambience.” It is a pattern of sound
reflection off the walls, ceiling, and floor. For example,
reverberation is the sound you hear just after you
shout in an empty gymnasium. Too much
reverberation in a recording can make the recorded
instrument sound distant or muddy. To reduce
reverberation:
• Place the mic closer to the sound source.
• Pick up electric instruments with a direct box or
cable.
• Use a room or studio with dead acoustics. The walls,
ceiling, and floor should be covered with a soundabsorbing material.
• Use directional microphones. Hypercardioid and
supercardioid patterns reject reverb more than
cardioid. Cardioid and bidirectional patterns
reject reverb equally well. Cardioid rejects reverb
more than an omnidirectional pattern at the
same distance:
Omnidirectional 0.0 dB
Cardioid -4.8 dB
Bidirectional -4.8 dB
Supercardioid -5.7 dB
Hypercardioid -6.0 dB
3
How to reduce background noise
• Stop the noise at its source: turn off appliances and
air conditioning; wait for airplanes to pass; close and
seal doors and windows; use a quiet room.
• Mike close with directional mics.
• Pick up electric instruments with direct boxes or
cables.
• Aim the null of the polar pattern at the offending
noise source. The null is the angle off-axis where the
mic is least sensitive. Different polar patterns have
nulls at different angles. Shown below (Figure 1) are
the null angles for various polar patterns:
Cardioid 180 degrees
Supercardioid 125 degrees
Hypercardioid 110 degrees
Bidirectional 90 degrees
How to reduce leakage
Leakage (also called bleed or spill) is the overlap of
sound from an instrument into another instrument’s
microphone. For example, if you’re miking drums and
piano each with it’s own microphone, any drum
sound picked up by the piano mic is leakage. To
reduce leakage:
• Mike close with directional microphones.
• When recording, overdub instruments one at a time
on each track of a multitrack recorder.
• Pick up electric instruments with direct boxes or
cables.
• Use a room or studio with dead acoustics. The walls,
ceiling, and floor should be covered with sound
absorbing material.
• Aim the null of the polar pattern at the undesired
sound source. For example, suppose you’re miking
two adjacent tom-toms with two hypercardioid
mics. The null of the hypercardioid is 110 degrees
off-axis. Angle each mic so that its null aims at the
adjacent tom-tom.
• Use a Differioid mic on vocals such as the Crown
CM-310A or CM-311A.
How to pick up sound at a distance
The farther you place a microphone from a sound
source, the more reverberation, leakage, and background noise you pick up. Also, you hear more mixer
noise compared to the signal because the mixer gain
must be higher with distant miking.
To clearly pick up sound at a distance:
• Use a microphone with low self-noise (say, less
than 22 dB SPL), such as the CM-200A, CM-700,
CM-150, any PCC, or any PZM® (see the Crown
Boundary Mic Application Guide).
• Boost the presence range on your mixer’s EQ
(around 5 kHz).
• If necessary, compensate for air losses at high
frequencies by boosting EQ around 15 kHz.
• Use directional microphones. You can place a
directional mic farther from its source than an
omnidirectional mic and pick up the same amount
of reverberation. The table below shows the distance
multiplier for each pattern (Figure 2):
Omnidirectional 1.0 dB
Cardioid 1.7 dB
Bidirectional 1.7 dB
Supercardioid 1.9 dB
Hypercardioid 2.0 dB
Cardioid A = 1.7
Supercardoid A = 1.9
Hypercardoid A = 2
Shotgun B = 3 to 10
depending on length
For example, if an omni mic is 1 foot from a sound
source, you can place a supercardioid mic at 1.9 feet
and pick up the same amount of reverb as the omni.
4
How to reduce the phase
cancellations between two mics
If two microphones pick up the same sound source
at different distances, and their signals are fed to the
same channel, this might cause phase cancellations.
These are peaks and dips in the frequency response
caused by various frequencies combining out-ofphase. The result is a colored, filtered tone quality.
To reduce phase cancellations between two microphones:
• Mike close.
• Spread instruments farther apart.
• Follow the 3 to 1 rule (Figure 3): The distance
between mics should be at least three times the micto-source distance. For example, if two microphones
are each 1 foot from their sound sources, the mics
should be at least 3 feet apart to prevent phase
cancellations.
As described in the Crown Boundary Mic Application
Guide, these situations can cause phase cancellations
which give a strange tone quality. Solve the problem
by using Crown PZM or PCC microphones mounted
to the piano lid, wall, floor, or other large flat surface.
How to reduce handling noise
and stand thumps
• Use an omnidirectional microphone such as a
PZM.
• Use a directional microphone with low sensitivity to
handling noise and thumps, such as the CM-200A,
CM-310A, or any PCC.
• Use a directional microphone with an internal shock
mount.
• Use a shock-mount stand adapter on a mic stand.
• Place the mic stand on foam or sponges.
How to reduce proximity effect
Proximity effect is the bass boost you hear when you
mike close with a single-D directional microphone.
“Single-D” means that the microphone has a single
distance from its front sound entry to the rear sound
entry. The closer the mic is to the sound source, the
more bass you hear. To reduce proximity effect:
• Use an omni directional microphone.
• Turn down the excess bass with your mixer’s EQ.
• Don’t use two mics when one will do the job. For
example, use just one mic on a lectern. If the talker
wanders, use a lavalier mic instead.
How to reduce phase cancellations
from surface reflections
Sometimes you must place a microphone near a hard
reflective surface. Situations where this might occur
are reinforcing drama, musicals, or opera with the
microphones near the stage floor, recording a piano
with the mic near the raised lid, or recording an
instrument surrounded by reflective baffles.
How to reduce pop
Pop is an explosive breath sound produced by the
letters “p”, “b”, or “t”. When a person says words
containing these sounds, a turbulent puff of air is
forced from the mouth. This air puff hits the microphone and makes a thump or little explosion called a
“pop”.
To reduce pop:
• Use an omnidirectional microphone.
• Use a microphone with a built-in pop filter or ball
shaped grille, such as the Crown CM-200A or
CM-310A.
• Place an external foam pop filter on the microphone.
• Place the microphone out of the path of pop travel above, below, or to the side of the mouth.
• Roll off low frequencies below 100 Hz.
5
Loading...