JBL - Dividing Network - Instruction Manual OM22

P U B L I C A T I O N OM22-3
JBL
JBL
DIVIDING
NETWORK
INSTRUCTION MANUAL
James B. Lansing Sound, Inc. maintains a Tech­
nical Service Department, to help JBL owners with
their individual problems. If you cannot find the
answer you need in published JBL literature or
obtain it from your Audio Specialist,
please
write us.
All JBL precision transducers are fully guaran­
teed against defects in materials and workman­
ship. Be sure to fill out and mail the warranty card
immediately.
APPLICATION
J B L p r e c i s i o n n e t w o r k s use c i r c u i t s c a r e f u l l y de­
signed to give an imperceptible t r a n s i t i o n f r o m
low to h i g h frequency transducers. U n l i k e o r d i n a r y
all-purpose n e t w o r k s , each J B L c i r c u i t is specifi­
cally engineered to m a t c h the c h a r a c t e r i s t i c s o f
the J B L transducers w i t h w h i c h i t is used, and
should n o t be connected to components f o r w h i c h
i t is not designed. Components w h i c h m a t c h each
of the J B L d i v i d i n g n e t w o r k s are l i s t e d i n the
table below:
LOW
HIGH
SHIPPING
HIGH
INPUT
NETWORK CROSSOVER FREQUENCY FREQUENCY FREQUENCY
WEIGHT
MODEL FREQUENCY TRANSDUCER TRANSDUCER CONTROL IMPEDANCE
(OHMS)
(LBS.)
500
150-4's
150-4C
LX5
500
LE15A
LX7
500
LE14A
N1200
1200
LX10
Strapping
Bar
16
375, LE175, 3-position
switch
LE85
8
10
LEI 75
3-position
switch
8
10
0130, D131,
130A, 130B's
LE175
3-position
switch
8
9
1500
LE14A
LE175
Continuously
variable
8
3
LX8
2000
LE14A
LE20
3-position
switch
8
3
LX11
2500
LE10A
LE20
3-position
switch
8
3
LX2
2500
D123, D208,
D216
LE20
Continuously
variable
8
3
N2400
2500
D130, 0131,
D123
075
Continuously
variable
8
4
N7000
7000
Any two-way
system
075
Continuously
variable
4 to 16
3
N500
375
16
SOPHISTICATED CIRCUITRY
D i v i d i n g n e t w o r k s a r e used i n t w o - w a y l o u d ­
speaker systems to electrically channel l o w tones
to the bass loudspeaker and h i g h notes and over­
tones to the h i g h frequency transducer.
I f a d i v i d i n g n e t w o r k is to f u l f i l l i t s f u n c t i o n w i t h ­
out compromise, i t m u s t be able to handle extreme
v a r i a t i o n s i n dynamics, the f u l l range of audio
frequencies, complex t r a n s i e n t s , and the v a r y i n g
impedance o f a loudspeaker load.
J B L d i v i d i n g n e t w o r k s are carefully designed to
complement the exact characteristics of the J B L
transducers w i t h w h i c h they are to be used. Each
n e t w o r k c i r c u i t controls the s i g n a l to the h i g h
and low frequency transducers i n such a w a y t h a t
smooth acoustic response is m a i n t a i n e d t h r o u g h
the f u l l audio spectrum. Thus, the effects of i n d i ­
v i d u a l speaker characteristics, impedance fluctua­
tions, and the physical separation of the t w o sound
sources are all taken into account i n the complete
system design.
N a t u r a l l y , s u c h s o p h i s t i c a t e d e n g i n e e r i n g de­
mands v e r y close tolerances i n p r o d u c t i o n i f a l l the
benefits of the design approach are to be realized.
O r d i n a r y networks, f o r example, often use electro­
l y t i c capacitors w i t h tolerances of plus or m i n u s
2 0 % . Response t h r o u g h the crossover r e g i o n is
ragged, and characteristics v a r y f r o m u n i t to u n i t .
A l l J B L n e t w o r k s , on the other hand, use only noni n d u c t i v e paper or m y l a r dielectric capacitors ( n o t
electrolytic u n i t s ) i n d i v i d u a l l y tested to meet J B L
tolerances. T h e special inductors used i n J B L net­
w o r k s have extremely low i n s e r t i o n loss so t h a t
none o f t h e d r i v i n g p o w e r t o t h e l o u d s p e a k e r
system is wasted i n the n e t w o r k . Each i n d u c t o r
is c a l i b r a t e d on a sensitive electronic b r i d g e and
its value set precisely. T o meet J B L p r o d u c t i o n
tolerances, n e t w o r k components m u s t check o u t
w i t h i n plus or m i n u s 1 % o f the established design
value.
MOUNTING IN JBL ENCLOSURES
J B L d i v i d i n g n e t w o r k s are n o r m a l l y i n s t a l l e d i n
the back panel o f the loudspeaker
enclosure. I n
J B L enclosures, t h e y m a y be easily i n s t a l l e d d i ­
r e c t l y i n t o the m o u n t i n g hole w h i c h is p r o v i d e d .
M a k e sure t h a t the w h i t e t u b u l a r gasket is i n place
a r o u n d the n e t w o r k flange. Center the n e t w o r k
i n t o the m o u n t i n g hole and secure by d r i v i n g f o u r
# 6 x % " r o u n d head wood screws i n t o the outside
surface o f the panel. ( T o i n s t a l l the L X 4 - 2 net­
w o r k i n t o the standard cutout, the F 2 m o u n t i n g
flange
is r e q u i r e d . )
MOUNTING IN CUSTOM ENCLOSURES
Dimensions f o r the r e q u i r e d m o u n t i n g hole are
shown i n the d i a g r a m . ( T o m o u n t the L X 4 - 2 i n
a c u t o u t of t h i s size, the F 2 m o u n t i n g flange is
required.)
I f y o u m o u n t the n e t w o r k i n the same c o m p a r t ­
m e n t as the l o w frequency d r i v e r , make sure t h a t
the m o u n t i n g hole is cut exactly. O t h e r w i s e , the
w h i t e t u b u l a r m o u n t i n g gasket w i l l n o t seal p r o p ­
e r l y , and the r e s u l t i n g a i r leaks m a y i n t r o d u c e
objectionable hisses and whistles i n t o the system.
ADJUSTING HIGH FREQUENCY GAIN
Since the h i g h frequency characteristics o f rooms
cannot be predicted, each J B L d i v i d i n g n e t w o r k
is p r o v i d e d w i t h a h i g h frequency level c o n t r o l ,
w h i c h makes i t possible to achieve a r e a l i s t i c t o n a l
. balance under a v a r i e t y o f r o o m conditions. The
acoustics of y o u r l i s t e n i n g room and y o u r personal
l i s t e n i n g taste w i l l dictate the s e t t i n g w h i c h w i l l
p r o v i d e the most pleasing performance.
T h e c o n t r o l enables you to a d j u s t the power fed t o
the h i g h frequency transducer. I t does not affect
the crossover frequency, nor does i t l i m i t the upper
frequency response of the loudspeaker system.
Some e x p e r i m e n t a t i o n w i t h t h i s c o n t r o l is usually
necessary w h e n the system is f i r s t installed i n i t s
p e r m a n e n t location. I f musical r e p r o d u c t i o n seems
t o be s h r i l l and edgy, t u r n the c o n t r o l counterclock­
wise to a lower s e t t i n g . I f i t seems dead and dull,
t u r n clockwise to a h i g h e r s e t t i n g . C o m p a r a t i v e
l i s t e n i n g tests should be made at the usual l i s t e n ­
i n g location. Once the c o n t r o l is set f o r best overall
results, i t need not be changed. Y o u can compen­
sate f o r a d d i t i o n a l differences i n source m a t e r i a l
w i t h y o u r preamplifier controls.
THE MODEL N500
T h e J B L N500 d i v i d i n g n e t w o r k is a professional
u n i t designed p r i m a r i l y f o r t h e a t e r i n s t a l l a t i o n s .
I t is usually mounted on top o f the enclosure or
i n some other visible and convenient location.
A l l t e r m i n a l screws l y i n g on the w h i t e l i n e are
common. T h e o u t p u t screws on t h i s line should be
connected to the black speaker t e r m i n a l s . T h e t w o
screws m a r k e d " L F " are i n t e r n a l l y connected so
t h a t connecting an L F d r i v e r to each set o f posts
effectively connects the d r i v e r s i n parallel.
T h e g a i n o f t h e h i g h f r e q u e n c y u n i t m a y be
adjusted by c h a n g i n g the p o s i t i o n o f the s t r a p p i n g
bar. Zero p o s i t i o n provides the m a x i m u m i n t e n s i t y
level of the H F u n i t . Each successive step lowers
the H F level one db.
CONNECTING JBL NETWORKS
N E T W O R K I M P E D A N C E A l l J B L dividing net­
works are matched to the characteristic impedance
of the transducers w i t h which they are used. Model
N500 is a 16-ohm network and should be connected
to the 16-ohm amplifier tap for most efficient power
transfer. A l l other J B L networks w i l l operate most
efficiently when connected to the 8-ohm amplifier
tap, although the 4-ohm or the 16-ohm tap can be
used w i t h o u t danger of damage to amplifier or loud­
speakers.
W I R E SIZES
I n f a c t o r y - i n s t a l l e d J B L systems,
18-gage stranded insulated w i r e is used f o r connec­
t i o n o f components. I n home i n s t a l l a t i o n s , 18-gage
s t r a n d e d or solid w i r e or o r d i n a r y c o m m e r c i a l
l a m p c o r d m a y be used f o r speaker-amplifier con­
nections up to 50 feet.
C O N N E C T I N G TO A M P L I F I E R
Fasten the
leads f r o m y o u r amplifier to the t w o push-type
t e r m i n a l posts on the face o f the d i v i d i n g n e t w o r k .
T h e " B " or black post connects t o the black, or
common, lead. T h e " R " or red post connects to the
8 or 16 ohm amplifier tap. N o soldering is r e q u i r e d .
S i m p l y depress the colored b u t t o n , i n s e r t the bare
end o f the lead w i r e , and release.
C O N N E C T I N G TO SPEAKERS
M o s t J B L net­
w o r k s are m o u n t e d on an escutcheon plate w h i c h
f i t s i n t o t h e s t a n d a r d m o u n t i n g c u t o u t on t h e
enclosure. Lead w i r e s f r o m the speakers
are
b r o u g h t o u t to the push-type t e r m i n a l posts on
the panel t h r o u g h eyelets i n the escutcheon plate.
Proper connections o f speakers to the v a r i o u s J B L
n e t w o r k s are explained below. Care should be t a k e n
to follow connecting i n s t r u c t i o n s exactly to ensure
t h a t the system w i l l operate i n phase: t h a t is, so
t h a t a s i g n a l f r o m the amplifier w i l l cause b o t h
d i a p h r a g m s to move i n the same d i r e c t i o n at the
same t i m e .
CONNECTING THE LX11
E m e r g i n g f r o m the
chassis o f the L X 1 1 n e t w o r k are f o u r w i r e s : t w o
black, one green and one red. Connect the green
w i r e to the red t e r m i n a l post of the L E 1 0 A low
frequency
loudspeaker. Connect the red w i r e to
the red t e r m i n a l post of the L E 2 0 h i g h
frequency
transducer. Connect the black w i r e s to the black
posts of the speakers. Since these t w o w i r e s are
connected i n the i n t e r n a l c i r c u i t r y of the net­
w o r k , either black w i r e may be connected to e i t h e r
speaker.
CONNECTING THE LX8
The L X 8 n e t w o r k is
connected i n the same w a y as the L X 1 1 . Connect
the g r e e n w i r e t o t h e r e d t e r m i n a l post o f t h e
L E 1 4 A low frequency
loudspeaker. Connect the
red w i r e to the red t e r m i n a l post o f the L E 2 0 h i g h
frequency transducer. Connect the black w i r e s to
the black posts o f the speakers — either w i r e to
e i t h e r speaker.
C O N N E C T I N G T H E N400, N1200, N2400 and L X 2 .
Each of these four dividing networks is connected as
shown i n the diagram below:
Extended Range
or low frequency
speaker
network
To Amplifier
High frequency
transducer
C O N N E C T I N G T H E L X 5 , LX13, and LX10. These
networks are connected to speakers as shown i n the
diagram below:
Low frequency
speaker
Network
To Amplifier
High frequency
transducer and
horn or horn/lens
C O N N E C T I N G T H E N7000
T h e N7000 d i v i d ­
i n g n e t w o r k provides a means o f a d d i n g the 075 to
e x i s t i n g h i g h - q u a l i t y t w o - w a y loudspeaker sys­
tems t o o b t a i n added b r i l l i a n c e i n the v e r y h i g h
frequencies. I t is connected to the h i g h frequency
t e r m i n a l s o f the m a i n d i v i d i n g n e t w o r k as shown
i n the d i a g r a m s b e l o w :
Low frequency
speaker
High frequency
transducer and
horn or horn/lens
Main
Network
075
To
Amplifier
.N400, N500 or N1200
Low frequency
speaker
High frequency
transducer and
horn or horn/lens
Main
Network
075
N7000
To
Amplifier
L X 5 or L X 7
JAMES B. LANSING SOUND, INC.,
3249 CASITAS AVE., LOS ANGELES 39, CALIF.