Brüel & Kjær 4131/32 User guide
One-inch
Condenser Microphones
Microphone
Cartridges Type
4131/32
Cathode Followers Type
2612/2613,
2630
Accessories
Precision
condenser
microphones
for
measurement
purpose
. Each
microphone
is
individually
cali-
brated.
Frequency
range
of
calibration
20-
20ooo
c/
s.
The
4132
fulfils
the
requirements
of
the
American
Standard
A.S.A. Z. 24.8-1949.
BHUEL
&
KJ~H
·
Nrerum,
Denmark
.
ey[;'
80
05 00
.
~
BRUKJA,
Copenhagen
. Telex;
5316
4131.4132
I
/
One-inch
Condenser Microphones
AUGUST
1962
Contents
Condenser Microphones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Description
of
the
Equipment
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Principle
of
the
Condenser
Microphone
. . . . . . . . . . . . . . . . . . . . . . . . . . 3
Definition
of
Free-Field
and
Pressure
Response
. . . . . . . . . . . . . . . . . . . . 6
Random
Incidence
Response
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 'l
Description:
Microphone
Cartridges
4131-4132
. . . . . . . . . . . . . . . . . . . . 7
Cathode
Followers
2612-2613 . . . . . . . . . . . . . . . . . . . . . . . . 9
General Characteristics:
1.
Sensitivity
...................................................
13
2.
Frequency
Response
.......
.
......
..
..........................
14
3.
Phase
Characteristics
........................................
15
4.
Free
Field
Corrections
........................................
15
5.
Directional
Characteristics
....................................
16
6.
Dynamic
Range,
Noise
and
Distortion
........................
18
7.
Equivalent
Volume
..........................................
19
8.
Influence
of
the
Polarization
Voltage
. . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.
Temperature
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.
Static
Ambient
Pr
ess
ure
......................................
21
11.
Magnetic
Fields
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
12.
Vibrations
...................................................
22
13.
Humidity
....................................................
23
Modification
of
the
pressure
equalization
..........................
24
Comparison
Type
4132 -
Type
WE
640
AA
........................
25
Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Random
Incidence
Corrector
UA 0055
..
.
...........................
26
Wind
Screen
and
Nose
Cone,
UA 0050, UA 0051
...•................
28
Microphone
Stands
UA 0026,
UA
4122
..............................
31
Extension
Cabl~s
AO
0027-28-29,
AR 0001
........................
31
Adaptor
UA
0030
................................................
32
Flexible
Extension
Rod
UA
0039
..................................
32
Couplers
DB
0138-160-161
......................................
32
Two-Channel
Selector
4408
........................................
33
Microphone
Power
Supply
2801
................................
,
...
34
Cathode
Follower
2630
.................................
.
........
35
Microphone Calibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
(Pistonphone
4220,
Microphone
Calibration
Apparatus
4142,
Electrostatic
Actuator
UA
0023,
Noise
Source
4240)
Cathode
Followers
Part Numbers
....................................
41
Condenser Microphones
General.
Description
of
the
Equipment.
A
comp
l
ete
microphone
consists
of
a
microphone
cartridge
and
a
cathode
follower
for
impedance
conversion,
allowing
long
cables
and
relatively
low
input
impedance
amplifiers
to
be
used
between
the
microphone
and
the
measuring
instrument.
The
microphone
cartridge
is
screwed
onto
the
housing
of
the
cathode
follower
making
a
small,
rugged
unit.
Fig. 1.
Microphone
Cartridge
Cathode Follower
L - / Gooseneck Connecting Plug
----
-
-
I~
rrr
I2J:s;miliilliiiiiii\liil\\ili\il\iLliiiliiiliiilii
IIIli
:tl
I 6
-
---
-=---
1
59203
Fig.
1.
Complete
Microphone,
consisting
of
Microphone
Cartridge
Type
4131
or 4132
and
Cathode
Follower
Type
2612.
The
microphones
may
be
directly
connected
to
the
different
B&K
measuring
in
strumen
ts
which
are
provided
with
a
"Condenser
Microphone"
input
socket
fitting
the
microphone
connecting
plug.
Stabilized
plate
and
heater
voltages
for
the
cathode
follower
and
polarization
voltage
for
the
cartridge
are
avail-
able
on
this
seven-poled
socket.
The
microphones
may
also
be
used
with
other
equipment
when
operated
from
a
Microphone
Power
Supply
Type
2801
which
provides
the
necessary
voltages
in
the
same
conditions
as
the
measur-
ing
instruments,
or
with
the
Battery-driven
Cathode
Follower
Type
2630
(see
Accessories).
For
free-field
and
room-acoustic
measurements,
the
micro-
phones
should
be
placed
remotely
from
the
measuring
instruments,
since
these
would
often
disturb
the
sound
field
because
of
their
non-negligible
dimensions.
Different
types
of
microphone
stands
and
extension
cables
are
available
for
this
pu~pose
,
see
Accessories.
An
examp
le
of
measuring
equip-
ment
is
shown
on
Fig.
2.
Principle
of
the
Condenser Microphone.
A
condenser
microphone
consists
essentia
lly
of
a
thin
metallic
diaphragm
mounted
in
close
proximity
of
a
rigid
back
plate.
Diaphragm
and
back
plate
3
2812
,
UA
0028
4131
.
(4
132
)Microphone cartridge
2612
Cathode
follower
stand
Measuring
amplifier
159Z01
Fig.
2.
Typical
measuring
arrangement
for
sound
measurements:
one-inch
microphone
equipped
with
"goose-neck"
cathode
follower
connected
to
a
B & K Microphone
Amplifier.
are
electrically
insulated
from
each
other
and
constitute
the
electrodes
of
a
capacitor
.
See
Fig.
3.
Housing
and
insulator
form
with
the
diaphragm
a
closed
chamber,
which
is
only
in
communication
with
the
outside
for
slow
static
ambient
pressure
variations.
When
the
microphone
is
exposed
to a
sound
pressure,
the
diaphragm
is
submitted
to
an
alternating
force
proportional
to
the
pressure
and
the
diaphragm
area.
The
consequent
move-
ment
of
the
diaphragm
varies
the
capacity,
and
these
variations
are
trans-
duced
into
an
AC
voltage
component
if
a
constant
charge
is
present
between
the
electrodes.
The
charge
is
obtained
by
means
of
a
stabilized
DC
polari-
zation
voltage,
and
it
remains
constant
as
long
as
the
charging
time
constant
of
the
circuit
is
much
long
er
than
the
period
of
the
sound
pressure
variations.
It
is
possible
by
careful
design
to
maintain
the
proportionality
of
the
AC
output
voltage
to
the
sound
pressure
within
a
wide
frequency
range
and
an
extended
dynamic
range.
The
widest
linear
frequency
range
for
the
pressure
response
is
obtained
if
the
resonance
of
the
mechanical
system
(diaphragm)
is
critically
damped.
This
is
realized
by
adjusting
the
mechanical
damping
of
the
air
cushion
between
electrodes
by
means
of
holes
in
the
back
plate.
The
low
frequency
limit
of
the
lin
ear
range
is
set
by
the
"cut-off"
(or
time
constant)
of
the
microphone
cartridge
circuit.
Referring
to
the
schematic
diagram
of
Fig.
4
the
cut-off
frequency
is
equal
to:
2
.n
(C
+ C + C ) Rt
Re
S 1 Rt +
Re
4
Since
the
semitivity
of
th
e
microphon
e is
determined
by
the
re
lative
variation
of
capacity
L1
C/
(C
+
Cs
+ Ct),
the
total
parallel
capacity
should
be
made
as
sma
ll
as
possibl
e.
The
first
amplifier
stage
is
therefore
built
in
the
same
housing
as
the
microphone.
A
cathode
follower
stage
is e
mployed,
because
s
mall
parallel
capacity
requires
high
R1
and
Re
in
order
to
obtain
a
satis-
factory
low
limiting
frequency.
Dia
Back
plate
Hole for
static
pressure
equalization
Fig. 3.
Schematic
co
nstruction
of
a
condenser
microphone
cartridge.
Mechanical
iH
.·
..
Cartridge
Electrical
Mass
Mechamcal Damping
Cathode
Follower
162161
Polarization
Circuit
C =
Polarized
cartridge
capacity
AC
= Variation of capacity
Cs
=
Stray
capacity
of
connection
to
cathode
follower
Ri,Ci
= Input impedance of
cathode
follower
Fig.
4.
Simplified
diagram
of
the
Condenser
Microphone.
(The
electrical
leakage
in
the
cartridge is neglected).
Definitions
of
Free-field
and
Pressure
Response.
The
Free-field
Response
of
a
microphone
is
the
ratio
of
the
1:.m.s.
output
voltage
to
the
r.m.s.
sound
pressure
existing
in
the
free
field
at
the
micro-
phone
location
with
the
microphone
removed
from
the
sound
field.
The
Pressure
Response
of
a
microphone
is
the
ratio
of
the
r.m.s.
output
·
voltage
to
the
r.m.s.
sound
pressure,
uniformly
applied
over
the
diaphragm.
The
two
definitions
coincide
for
a
microphone
having
negligible
dimensions
with
respect
to
the
sound
wavelength.
In
the
case
of
the
B&K
one-inch
microphones
this
is
practically
fulfilled
up
to
about
1400 c/s,
where
the
wavelength
attains
ten
times
the
diameter
of
the
microphone
(
i.
e. 240
mm).
The
difference
in
response
is
then
less
than
a
small
fraction
of
a
decibel.*)
Free-Field
Response="t
Pressure
Response=
I;
vo~ts~L___Mi-crophone~IC2~~-------c;;....--~
Wavelength
Sound
pressure
p
0
______
_
0° incidence
f62f60
Fig. 5.
Definitions
of
Free-field
and
Pressure
Response.
At
higher
frequencies
the
diffractions
of
the
sound
waves
on
the
microphone
produce
an
appreciable
change
in
the
resulting
sound
pressure
acting
on
the
microphone
diaphragms
as
illustrated
on
Fig.
5.
The
difference
p1
-
po
, C{\lled
free-field
correction
,
depends
on
the
orientation
of
the
microphone
w1th
respect
to
the
direction
of
propagation
of
the
sound
and
on
the
external
dimensions
of
the
microphone
(in
particular
those
of
the
front
and
of
fitted
protective
grids
or
"nose
cones").
The
free-field
behaviour
of
a
microphone
is
thus
described
by
means
of
a
set
of
free-field
corrections
curves
for
various
incidences,
which
have
been
measured
on
a
model
of
the
microphone
(see B&K
Tethnical
Review
Nos.
1 & 2-1959),
and
which
should
be
added
to
the
pressure
frequency
curve
of
the
microphone
in
each
particular
case.
See
Figs.
13
and
14.
For
~nicrophones
intended
for
ffee-field
work
it
is
possible
to
give
the
diaphragm
resonance
such
a
damping
that
the
normal
incidence
free-field
*)
In
the
particular
case
of
the
90°
incidence
(
parallel
to
diaphragm)
the
difference
in
response
remains
negligible
up
to
10
kc
/s.
6
•
corrections
are
compensated
for
up
to
frequencies
well
above
the
resonance
frequency,
in
order
to
obtain
the
flattest
possible
frequency
response.
Random
Incidence
Response.
In
the
important
case
of
indoor
sound
measurements,
where
a
great
part
of
the
sound
pressure
is
caused
by
sound
waves
which
have
been
reflected
in
au
·
possible
ways
before
impinging
on
the
microphone,
all
incidences
have
to
be
considered
simultaneously
creating
what
is
called
random
incidence
or
diffuse
field
conditions.
The
International
Electrotechnical
Commission
(T.C. 29, W.G. 8)
has
edicted
a
practical
rule
for
the
cal-
culation
of
the
random
incidence
response
as
the
root
mean
square
of
the
free-field
responses
for
different
orientations,
taking
into
account
the
area
of
the
corresponding
surface
elements.
See p. 16.
According
to
this
rule
the
diffuse
field
corrections
are
found
to
be
much
smaller
than
the
free-
field
corrections
in
the
case
of
the
B&K
microphones.
For
the
one-inch
microphones
the
difference
between
the
pressure
response
and
the
random
incidence
response
is
less
than
4
db
up
to
around
20
kc
/s.
A
microphone
with
flat
pressure
frequency
characteristic
should
consequently
be
preferred
for
indoor
measurements.
However,
by
mounting
specially
designed
devices
instead
of
the
protective
grid
(see
Accessories),
the
respnose
may
be
made
practically
independent
of
the
angle
of
incidence
in
an
extended
frequency
range.
The
free-field
and
diffuse-field
responses
are
then
identical,
and
the
same
microphone
will
suit
for
both
outdoor
and
indoor
measure-
ments.
Description
of
the Condenser Microphone Cartrldges
Type
4131
and
4132.
Two
slightly
different
one-inch
microphone
carlrid
.ges
are
available:
(
1)
the
Microphone
Cartridge
Type
4131
designed
for
free--field
measure-
mel)ls
and
featuring
a
normal
incidence
free-field
frequency
characteristic
whiph
is'
flat
up
to 18
kc
/s
(with
protecting
grid
mounted}.
(2)
the
Miciophone
Cartridge
Type
4132
presenting
a
pressure
frequency
characteristic
which
is
flat
up
to 7
kc
/
s.
The
two
cartridges
have
basically
the
same
mechanical
construction
and
differ
only
by
the
damping
of
the
diaphragm
resonance.
The
resonance
is
over-
damped
in
the
case
of
Type
4131,
in
such
a
way
that
the
normal
incidence
free-field
pressure
increase
is
compensated
by
the
decrease
of
pressure
sen-
sitivity
up
to
18
kc
/
s.
In
the
case
of
Type
4132
the
resonance
is
approximately
critic~lly
damped
in
order
to
obtain
the
flattest
possible
pressure
freq~cy
response.
The
resonance
frequency
,
which
is
approximately
the
same
for
the
~tridges,
is
around
7.5
kc
/s.
The
damping
is
controlled
by
means
of
appropriate
holes
in
the
back
plate
and
by
adjusting
·
the
tension
of
the
diaphragm.
7
Towards
the
low
frequencies
the
response
of
the
cartridges
is
only
affected
by
the
influence
of
the
pressure
equalizing
arrangement.
This
arrangement
consists
of
a
capillary
leakage
hole
through
which
the
equalization
of
the
static
air
pressure
on
both
sides
of
the
diaphragm
is
obtained
at
a
suitable
rate.
The
influence
of
ambient
pressure
(or
altitude)
variations
on
the
microphone
sensitivity
may
be
minimized
by
proper
design
of
the
pressure
equalization
hole.
(For
adjustment
of
the
pressure
equalization
see
p. 24).
In
the
case
of
the
one
inch
cartridges,
the
equalization
hole
is
situated
in
front
of
the
grid-
and
coupler
mounting-thread
in
order
to
enable
the
pressure
equalization
to
be
obtained
also
in
the
case
of
closed
cavity
measurements.
The
time
constant
of
the
pressure
equalization
of
Types
4131-4132 is o.05
second.
This
corresponds
to
a - 3
db
cut-off
frequency
of
3 c/s
approximately,
and
will
not
influence
the
measurements,
since
the
-3
db
low
frequency
cut-off
of
the
complete
microphone
is
10
cis.
The
mechanical
construction
of
the
cartridges
is
shown
on
Fig.
6.
The
choice
of
the
materials
and
th~
design
of
the
suspensions
of
the
different
parts
are
made
principally
with
a
view
to
obtaining
the
best
possible
long-term
stability
and
temperature
independency
of
the
sensitivity
.
The
cartridges
are
subjected
to
a
complete
artificial
aging
process
during
manufacture.
The
basic
parts
are
made
of
high
nickel
alloy
(K-Monel).
The
insulator
used
is
silicone
treated
qua
ftz
and
for
guaranteeing
a
disturbance-free
connection
to
the
cathode
follower,
gold
contacts
are
used.
The
diaphragm
is
made
of
a 4
fl
thick
nickel
plate
and
is
mounted
at
a
distance
of
22
fl
from
the
back
plate.
This
distance
is
reduced
to
20
fl
when
the
200 V
polarization
voltage
is
applied.
The
polarized
cartridge capacity,
which
is
of
the
order
of
60
pF,
is
measured
individually
for
each
cartridge
(see
the
calibration
chart).
The
insulation
is
verified
as
higher
than
105
M.
Q.
2311mm60
NS
2
I
.e
(0.910" 60
NS
2)
__
_
__
___
_l
_____
___
22.7Smm
E~-
(0.896")
E~
I
':J~a
~~
r
I
~_g
~
I
~
l
~
~
'
~
b371mm-Dod
I
(0
.
936"
:to
.
oooaJ
I e•r t 161179
23.11
mm
60
NS
2 E
a>
E~
(0
.910" 60
NS
2)
~~
Mg
+
f>imensions
of
the
"one-inch"
microphone
cartridges
Type
4131-4132.
R
•
Fig.
6.
Exploded
view
of
a
one-inch
microphone
cartridge.
CAUTION.
On
no
account
should
the
diaphragm
which
is
only
4
p,
( o.00016")
thick
come
into
contact
with
fingers
or
other
objects.
The
protecting grid
should
only
be
removed
when
absolutely
necessary.
This
grid is
an
effective
protection
against
mechanical
damage
but
cannot
stop
liquids
or
dust
from
falling
on
the
diaphragm.
Should
the
diaphragm
become
contaminated
it
may
be
dried
off
with
cotton-wool
or a
very
soft
paint-brush
,
using
great
care,
and
if
necessary
a
proper
solvent.
The
diaphragm
will
not
normally
corrode,
but
any
appreciable
added
mass
will
change
the
frequency
response.
Description
of
the Cathode
Followers
Type
2612
and
2613.
The
Cathode
Followers
Type
2612
and
2613
are
designed
for
connection
to
the
B & K
Condenser
Microphone
Cartridges
or
Accelerometers,
transforming
the
high
source
impedance
of
the
transducer
to
a 750
.Q
output
impedance.
They
are
electrically
identical
units.
The
mechanical
construction,
however,
is
different
in
that
the
Cathode
Follower
Type
2612 is
fitted
to a
flexible
goose-neck,
while
Type
2613 is
supplied
with
a 2 m
long
multi-core
cable
as
shown
in
Cathode
Followers
Part
Numbers
(last
page).
The
outside
diameter
of
the
cathode
followers
is
identical
to
that
of
the
microphone
cartridges,
i.e. 23.77
mm
(o.936").
To
ensure
high
operating
stability
under
conditions
of
large
temperature
changes
and
external
vibration,
the
components
used
have
been
carefully
selected
and
are
mounted
_
on
glass
laminated
boards.
Use
has
been
made
of
silver
plated
printed
circuitry
and
the
amplifi!;~r
tube
chosen
meets
the
Mil-E1C
specifications.
The
complete
component
assembly
is
siliconetreated
which
provides
a
high
resistance
to
moisture.
In
the
interests
of
good
electrical
connection
and
low
noise
the
contact
between
cathode
follower
and
microphone
cartridge
is
made
from
solid
gold.
Before
delivery
each
cathode
follower
is
exposed
to
a
sound
.
pressure
of
9
Note:
Left
hand
thread
Unscrew
housing
by
turning
as
the
arrow
tndicates
159211;-
Basic
construction
of
the
Cathode
Fo
ll
ower
.
.-------------
-w----------------------
----
----------------------------
oooooooooooo
ooooooooooooooooo
oooooooooooooooooooooo
Br
ll
t!,!J•r
+
,_
...
JIDr.Ji,_,_,__l_.,
..
~~~~
..
.
w.
.
,_,_lQ_Q,.,.,Ji
.
M.C.
""'---,.,...~•
-
oo
-
KIOIIO
20000
q.
«1000
QP
0123
10
100
1000
10000
C/S
(1611/2111)
A I
16
19/tJ
Fig. 7.
Recording
of
the
ou
tput
from
a
Cathode
Follower
with
a
dummy
microphone
of 60
pF
when
exposed
to
a
sound
fie
ld
of
130
db
in
the
fre-
quency
range
from
20
to
20ooo
cis.
The
output
signal
is
at
any
fre
quency
more
than
50 db
below
that
obtained
with
the
microphone
cartridge
in
P.
lace.
130
db
where
the
microphony
is
measured
within
the
frequency
range
of
20
--
20ooo
c/s.
The
signallmicrophony
ratio
is
greater
than
50
db
with
reference
to
a
microphone
with
a
sensitivity
of
5
mV
/,ubar.
See
Fig.
7.
The
input
is
internally
shie
lded
by
means
of
a
"guard
ring"
which
is
con-
nected
to
the
cathode
of
the
tube.
In
this
way
the
input
capac
it
y is
reduced
to
an
absolute
minimum.
See
Fig.
8.
By
extending
the
internal
shi~ld
it
is
possible
to
use
the
microphone
cartridge
at
some
distance
from
the
ca
thode
follower.
See
Accessories:
Extension
Rod
UA
0039.
10
...
•
Microphone
Cartridge
r---------t-
Polarizing
Voltage
+
f592f3
Fig.
8.
Basic
diagram
of
a
cathode
follower
showing
the
principle
of
the
"guard
ring''
system.
Meters
Meters
of cablo
of
cable
AC
3029 AC3028
1s
used OS
Used
. ·A00027
inAO
00
28-29
1000
sao
200
100
50
20
20
10
8
10
-
-s
~
100'i's
1
m-
3.
33
feet
3 4 6 8 llOOS's 2 3 4 6 8 tlK'7's 2 3 4 5 6 8 100K'7's 2 3 4
0.1
6 8
1000KC
fs
1
59215
Fig.
9.
Graph
of
cathode
follower
high
frequency
performance
with
different
lengths
of
connecting
cable
attached
to
the
output.
To
illustrate
the
use
of
the
graph
the
standard
B & K
microphone
cables are
drawn
in.
The
cables
AC
3028
and
AC 3029 are
the
types
of
cable
used
by
B & K,
but
without
connecting
plugs
and
sockets
in
the
tnds.
11
The
Cathode
Follower
Type
2612
can
be
mounted
either
directly
on
one
of
the
B & K
Microphone
Amplifiers
or
Frequency
Analyzers,
or
connected
via
a
seven-conductor
extension
cable.
When
used
with
an
extension
cable
it
can
be
mounted
on
any
one
of
the
B & K
microphone
stands.
The
total
capacity
of
the
extension
cables
will,
to
a
certain
extent,
load
the
cathode
follower
and
lower
the
high
frequency
cut-off
point
which
wjll
produce
distortion
at
high
sound
pressure
levels. At
normal
levels,
this
will
only
be
of
importance
when
very
long
cables
are
used,
but
this
does
not
infer
any
serious
limitation
in
the
practical
use
of
the
microph9nes.
The
relationship
between
high
frequency
cut-off,
cable
length
and
harmonic
distortion
are
given
showing
the
limiting
values
in
Fig. 9.
Type
2613 is
intended
for
direct
mounting
on
one
of
the
B & K
Microphone
Stands
and
may
al
~
so
be
suspended
by
means
of
its
own
cable.
The
power
supplies
necessary
to
operate
the
cathode
followers
arc
provided
by
the
amplifier
via
the
multi-socket
at
the
front
panel,
qr
by
a
Microphohe
Power
Supply
Type
2801 (see
Accessories).
Technical Data.
Input
Impedance:
270 M,Q
in
parallel
with
3 ftftF.
Output
Impedance:
750 Q.
Transmission
Loss:
Voltage
loss:
o.8
db
± o.2 db.
Self-generated
Noise
Level:
Approx.
20
t-tV
with
the
input
loaded
by
a
capa-
citor
of
60
p,
,ftF.
{20
c/s- 20
kc
/s).
Maximum
Input
Voltage
for 4 %
Distortion:
20
V.
RMS
(with
load
impedance
>50
k.Q).
Tube:
EF
731 {5899) , S<
pecially
tested
for
low
microphony.
Accessory
included:
Input
Adapter
J J
2612.Jitting
the
B & K
coaxial
plugs,
for
direct
connection
of
accelerometers
etc.
instead
of
a
microphone
cartridge
.
(Contains
a
series
capaoitor
of
a few
thousand
pF
for
blocking
the
200 V
p;!ari~~
-
tion
voltag€l)
...._
-
Ground
Polarization
Voltage
200Y
D.C
.
Cathode
~
Filament
6.3Y
D.C
.
200mA
Plate
150Y
D.C
2mA
Connection
tor
4408
159216
Plug
connections
for
the
cathode
followers
(viewed
from
outside).
12
•
General
Characteristics
(Cartridges+
Cathode
Followers).
1.
Sensitivity.
The
sensitivity
of
both
cartridges
measured
at
the
output
of
the
associated
cathode
followers
are
within
the
limits
3.5- 6
mV
/,ubar.
Each
cartridge
is,
however,
individually
calibrated
and
supplied
with
its
specific
~
calibration
chart
when
delivered,
see
Fig.
10.
The
·
calibration
is
carried
out
at
250 c/s
and
with
a
cathode
follower
presenting
the
exact
nominal
character_istics:
gain
o.8
db
and
input
capacity
3
pF
(see
the
technical
data
for
the
cathode
followers).
The
open
circuit
sensitivity
,
which
is
calculated
from
the
overall
sensitivity,
[
is
also
indicated
on
the
caltbration
chart
together
with
the
polarized
cartridge
capacity.
When
this
capacity
is
exactly
60
pF
the
open
circuit
sensitivity
is 1.2
db
higher
~-
Uian
the
overall
sensitivity
measured
at
the
output
of
the
reference
cathode
follower
.
C.llbt-atlonChartfor
Condemer
Mkrophone
Cartridge
Type 4U1
S.rioiNo-73496
~J;,2
!.
~t!';/
&O
"'"'Hr ,an
dwlU.2
00V
r~~:r~~~i!Lr~
..
~
~
i:n~
.
~
~:r;
~
~
~(at
'~
4,
68
mY
,w
hr
-46,6 db N . V/
!'b
a r
C
a
.-t
rldra
o
pecn
e~i,..,ul
tHna
ltlri
t,af :
5,
37
mV/
I'
b&r
-45
,
4db
,..,
Y
/l'
ba
r
car:'i:.=;.~'."J]':':.:.
o ~
;
"
11
'•
;t!
,
;::"
,":
" l
0
"
~
=
-t0
.6
~C.,.utyat
l
k c/a
w
llh200V
p
ol
a
rl
u
tlon
67.1
"
"
-"
"
~
26
oC
Bar
ornatrlo
~
..
...
..
,.
767
llta
la
U•
•
H"
m
ldl
t.J
56
"•
S..nolth-lfy
U2!10e
/
a,
7
61;Wn
"'l-ll,&nd
w
lth200V
polartutiO
n
•olt
a
c•
~?!r1.~~~~::.~~~~:e':~2;;~
.
~~:"a·:::t:;:;
4.
22
mVi/<ber
-47
.5 d
bl't
.
1'1
1
.<
<ber
Ca<i.rtdceo~nclteultH,.al\l
•
lt¥
4.
84
m\I
'
Ub
&r
-46.3
..
clbre
.
IV
1
1'h<
cam.~~=·
n~~·
.
".:r:::.:o::~
':~
'
.
,~::
:'
"' on
11
, +1.5db
C
a....W,a
CapM
i
ty
at I
~
e.
a
with
200\1
pol
arl
ull
o"
61.0
pi"
[~
w
alentAifV
..
....,a
u\at"'
·' 0.
12
em'
Individual F..-quancy Ratpon1a1
~;
:~E:~~~;r~:JkE::~~;~~~
~-
((((11*'<
S...rn..,rrlzadSpaclrlntlonl
O....W.!M.
.......
to.GS
II
Inch l
23.77mml
'~'!:":::::
;::~6',lo
J
t~~
lw
..n-M
nel
+
&O"C
:
Amw-t,........,.
c:...rllc:l
ant
: a
ppro
•
.-o.2
db l
or
• 1
00
/, pr
auu
..
ctoanrt
.
~~~;'"'.~="!1
c:~n"o":
.."
,"
:
Jo~
~u
t
ll
an
o.l
clb,
'"
TeiTipe<e
tur
a
24
758
llelatlwa Huml<llt)l
62
•;,
Oat a
7-2-62
stcneturt
R.S
~:
0 0 0 0 0 0 0 0 0 0 0
~~~
0 0 0 0 0 0 D 0 0 0 0 0 0
OMoiO
t.
~
0 0 [
---,---
=
'~
:
-:-:-~
;
M
100 1000
C/5
10000
162Uf
~.:
0 0 0 0 0 0 0 D 0 0 D
~~
-
~
0 D 0 0 0 0 D 0 0 0 0 0 0
O
lri.lol~~
0 0
--+--
100
__:ci-1
1000
-1
CIS
10000
Fig.
10
.
Typical
calibration chart as
supplied
with
the
microphone
·,
·''
'·
a.
Data
foi;
Microphone
Cartridge
Type
4131.
b.
Data for
Microphone
Cartridge
Type
4132.
13
2.
Frequency
Response.
Each
microphone
cartridge
is
provided
with
an
individual
frequ
ency
respon
se
dete
rmined
by
th
e ele
ctrostatic
actuator
method
(Fig. 10).
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
lrQel
•
KJ•r
Broel
&
Kl~r
I
f::::=5db
ee
fiEld
re~
sure
0 0 0 0
'!4
0 0
~
0 0 'tf 0 0 0
~
0 0 ~ 0 2000 5000
0
~
0
~~
0 0 0 0 0 0 0
--
158
1't-
8
Fig.
11.
Typical
frequency
characteristics
of
the
Cartridge
Type
4131.
.-
-- -
c 0 0 Q 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
BrUel
& KJcar
BrUel
& KJcar
1SQO
--
Gl
-- ---- -
12oog
....
<
roc>e»
~
....
soon.
Gl
30~j
0
50
0 0
100
o '8' o o 500
0
~
0 2000 5000
10000
C/1
20000
()OI'IIon
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
159209
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 n 0
BrU•I &
ICJcar
BrOel
&
ICJcar
15()0
--
----
12QOi
c:
roo<
Qj
~
60°f
'
Qj
3QO~
I §
so
100
200 500
0
~ 0 2000 5000
10000
C/1
~
-
~
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
15921
0
Fig. 12.
Typical
pressure-response
phase
angle characteristics
of
the
micro-
phone
cartridges
(curves
drawn
in
full). Tile
dotted
curves
indicate
the
fre·
quency
characteristics
of
the
cartridges.
a.
Type
4131
b.
Type
4132
14
Fig.
11
shows
a
typ
'
ical
frequency
characteristic
of
the
Microphone
Cartridge
Type
4131
under
free
field
conditions
with
the
protecting
grid
in
place
and
with
the
sound
waves
impinging
perpendicularly
onto
the
microphone
dia-
phragm.
For
the
sake
of
convenience
the
pressure
response
is
also
shown.
The
increase
in
sound
pressure
at
higher
frequencies
is
compensated
for
in
the
constr
uction
of
the
cartridge
itself,
and
the
free
field
response
curve
shown
refer$,
therefore,
to
the
sound
pressure
present
before
the
microphone
was
placed
in
the
sound
field.
3.
Phase
Characteristics.
The
pressure
response
phase
angle
characteristics
for
the
complete
micro-
phones,
that
is
the
cartridge
and
a
cathode
follower,
can
be
seen
in
Fig.
12.
The
diaphragm
resonance
(90°
phase
angle)
,
which
is
approximately
critically
damped,
occurs
at
about
7.5
kc
/s.
4.
Free-field
Corrections.
The
pressure
increase
which
is
caused
by
the
reflections
of
free-field
sound
waves
on
the
microphone
diaphragm
becomes
appreciable
above
1
kc
/s.
The
corresponding
correction
curves,
which
are
valuable
for
both
cartridges
are
given
in
Fig. 13
and
14.
The
frequency
response
for
the
various
angles
of
incidence
is
obtained
by
adding
the
free-field
correction
to
the
pressure
10
db
8
Free
Field
corrections
for
11
iype
4131
and Type 4132 1
/v
--
0~
/
~
\
without
protecting grid.
]/
~
...........
j...--/
\ 1\
vv
'30° 'lLl
u_A
_j_
~v
'\
'
,/'
!/
/~
.......
±=--,
11
v
/
~
v
60~
--::;::::::.
~
_v
.....
~
---
........
\ j
-=
......
-... -'l\
--
r-
~
......
,
\\
-[-.... -
r-
........
90~
'\
r....
2
-.
,
............
~
180~\
\
"'
12~
\1
r'\
\\\
\
-4
-----RANDOM
INCIDENCE
15
f
llll
6 I I
~l
l
arrrroCL
7 (
fTTiA
JE
0°
lncidenc~
\\
1\\
B
t---
:::,
K
eo
l
~
\\
b • I I
0 1_1t
-11000 %
20
30
40
SDk%
70
158151
6 7 8 9
10
k%
15
2
Fig. 13.
Typical
free field
corrections
curves
to
be
added
to
the
pressure
characteristic
of
the
microphones
when
used
without
the
protecting
grid.
15
response
supplied
with
each
cartridge.
vVhen
mounting
a
Random
Incidence
Corr
e
ctor
or
a
Nose
Con
e
on
the
microphones
,
however
,
the
free-field
cor-
rections
are
practically
independent
of
the
incidence.
This
is
of
great
interest
wh
en
using
the
microphones
in
diffuse
sound
fields
(indoors).
See
Accessories.
The
random
corrections
are
calculated
according
to
the
recommendations
of
the
IEC
for
Sound
Level
Meters:
(S =
random
incidence
sensitivity):
S2 = o.017 X
S2
0 +o.129 X
S2
30
+ o.224 X
S2
60
+ o.259 X
S29o
+ o.224 X
S2
12o
+o.129 X
S21
5o +o.017 X S2
1so
So,
Sao,
Sao
. . . . . . S
180
=
sensitivity
at
the
angles
oo
, 30°, 60° . . . . . . 180°.
15
Free
field
corrections
for
db
Type
4131
and
Type
4132
with
protecting
grid.
10
~
~
;;.-"'--
-
~
--
---
"'=='==
---
----
--
-5
I
I I
I I
db
-
~7
( (
~~~
-1 L I
-10
r
1k%
3
I I \ I
!
ol
/ I 1\ I I
I
/
300..-V-\
\ I I i
I I
I v / . I \ i
!i
I I
j
I I vv \
\1\
I
v/v
1\ i
.I
I
~>
\. ! ; I
~
\I I ! ' I
p
,........v
x--
' \i I I I
V
_.......V
6
eJ'c~
"I
60\\
\. I i i
~
~\~0,
1\\
'r-o~OJ,..
!
__
...
\ \
-I--.
-
..........
9QO
\ I
180°
r--
-1s
~
I" \ \
~
~
\\
\
120°
~\~
I !
~\\
I
I !
\\\\
\\\1\
,
0°
Incidence
\\
.\
~
j8., i
'~
\
\'
6 7 8 9
10
15
20
\\
I
j\J
~
~
\
i
~
\
t
~
I
~
i
II
,.
ii/
~
\ '
I ii
I ;I
I ' I·
i !
~
I : I J\
I
I·
\I
"
30
40
50
k%
70
158/
50
Fig. 14.
Typical
free field
correction
curves
to
be
added
to
the
pressure
characteristic
of
the
microphones
when
used
with
the
protecting
grid.
5.
Directional
Patterns.
Because
b~th
types
of
cartridges
hav
e
the
san1e
mechanical
dimensions
their
directional
properties
are
identical
up
to
a
frequency
of
20ooo
c/s, Fig. 15.
NOTE:
·
Much
better
omnidirectional
properties
are
obtained
if
the
protecting
16
""'
····---With
prot•cti
ng
grid
-·-
----
Withprotectilggid
-------
With protecting
grid
·----
--
Withprotectmg
gnd
Fig.
15.
Typical
directional characteristics for
the
microphones.
grid
is
substituted
by
a
Random
Incidence
Corrector
UA
0055 (see
Fig.
30)
or
a
Nose
Cone
UA 0051 (see
Fig.
36).
17
6.
Dynamic
Range,
Noise
and Distortion.
The
lower
limit
of
th
e dy
nami
c range is set by
the
th
e
rm
al
noi
se level
of
the
cathode
follow
er.
With
a
microphon
e c
artridg
e
th
e
sen
s
iti
v
it
y
of
whi
ch
is 5 mVI
.ubar
this
limit
will be e
qual
to
a
sound
level
of
15
db
with
re
feren
ce
to
2 X 10-4
.u
bar m
eas
ured
with
a
weightin
g ne
twork
curve
A.
The
noise
level
of
the
C
athode
Follow
e
rs
Type 2612
and
2613 is
appro
x
imat
e-
ly
20
.uV (26
db
with
refe
rence
to
2 X
10
~
4
.ubar) me
asur
ed
with
a
capacitor
of
60 .u.uF
across
the
input
and
at
a
bandwidth
of
approximately
200
kc/s
(20
c/s-200
kc/s).
When
measured
in
1
h
octave
bands
the
noise
level
is
less
than
2 .uV (6
db
with
reference
to
2 X 10-4
.u
bar
)
except
at
frequencies
lower
tha~
120
cjs
where
it
is
less
than
5 .uV {14
db
with
reference
to
2 X 10-4
.ubar).
The
upper
limit
of
the
dynamic
range
is
set
by
the
harmonic
distortion,
and
is
approximately
146
db
for
4 %
total
harmonic
distortion.
See
Fig
. 16.
No
damage
will
be
caused
to
the
cartridge
if
a
sound
pressure
of
up
to
165
db
with
reference
to
2 X 10-4
.ubar
is us
ed
but
as
this
is
the
highest
S.P.L.
at
which
the
microphone
has
been
tested
it
is
not
recommended
to
exceed
thi
s va
lu
e.
Th
e
upp
er
limit
is also s
om
e
what
depe
nd
e
nt
on
th
e fre-
qu
ency, see Fig. 9.
10
%
9
8
7 0
6 I
5
~v
I.
~
3
tj
I J
2 / 0
/ .,
I--
0
.~
1
~..---.....-
vf
1-
--
....-
Volt
(12
QJ
0/o
0.5
0,6 0.8
1D
1.5
2 4 5 6 8
10
15
20
30
40
50
60
80
100
Volt
150
200
l.lbar
40
100
200
400
1mbar
2 4
1~
20mbar
db 106
114
120
126 134db
140
146
160dbre
. 0.00021Jbar
159208
Fig.
17.
C
utv
e
showing
th
e
mi
c
rophone
sens
itivity
vs. polariza
tion
voltage ut
full are
measured
on
th
e
cathode
follower
and
referred
to
a
complete
micro-
phone
with
a
sensitivity
of
5 mVI.ubar.
The
measuring
points
s.llown are
averages
mea
s
ured
in a
pistonphon
e
on
a
number
of
complete
microphones
at
50 cis.
18
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