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Index
Professional Division Warranty
Every J B L Professional Series transducer is guaranteed
against defects in material and w o r k m a n s h i p for a period of
five years. J B L electronic products are warranted for a
period of two years. J B L will replace defective parts and
make necessary repairs under this warranty if our exam-
ination reveals evidence of faulty w o r k m a n s h i p or material.
The warranty does not cover damage caused by misuse,
accident or neglect. J B L retains the exclusive right to make
such determination on the basis of factory inspection.
Moreover, because we believe that a fine loudspeaker,
like a fine musical instrument, should never wear out, we
will repair any J B L transducer free of charge without time
limitation if factory inspection discloses evidence of an
original manufacturing defect.
If it is impractical to return the product to the factory,
please write J B L describing the difficulty or malfunction.
J B L may, at its option, establish alternative repair proce-
dures or furnish replacement parts as appropriate.
Products returned to the factory must be shipped prepaid
and will not be accepted unless written authorization has
first been obtained.
The warranty on J B L products shall remain valid only
if repairs are performed by J B L or under its authorized
procedures, and provided that the serial n u m b e r on the
unit has not been defaced or removed.
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Specifications
Power Capacity'
75 Watts c o n t i n u o u s p r o g r a m
Crossover Frequencies
1500 and 6 0 0 0 Hz
Nominal I m p e d a n c e
8 o h m s
High Frequency Dispersion
9 0 ° horizontal and vertical
Frequency Response
4 5 - 1 5 , 0 0 0 Hz ± 3 d B
Sensitivity
4 2 d B at 30 teet with a 1-mW input
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averaged 5 0 0 to 2 5 0 0 Hz,
with controls set for flattest
response
81 d B at 10 feet with a 1-Watt input,
averaged 5 0 0 to 2 5 0 0 Hz, with
controls set for flattest response
Low Frequency Loudspeaker
Nominal Diameter
12 inches 30 c m
Voice Coil
3-inch (7.6 c m ) e d g e w o u n d c o p p e r
ribbon
Magnetic Assembly Weight
6.75 p o u n d s 3.1 kg
Flux Density
10,400 gauss
Sensitivity
4 2 d B
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Midrange Transducer
Nominal Diameter
5 inches 13 c m
Voice Coil
%-inch (2.2 c m ) c o p p e r
Magnetic Assembly Weight
2.75 p o u n d s 1.2 kg
Flux Density
16,500 gauss
Sensitivity
(averaged 1-3 k H z )
46 d B
High Frequency Direct Radiator
N o m i n a l Diameter
1.4 inches 3.6 c m
Voice Coil
%-inch (1.6 c m ) c o p p e r
Magnetic Assembly Weight
1.6 p o u n d s 0.7 kg
Flux Density
15,000 gauss
Sensitivity
(averaged above 2 kHz)
47 d B
Finish
Textured gray or oiled walnut with
black fabric grille
Dimensions
2 3 V x 1 4 V x 1 1 V d e e p
6 0 x 3 6 x 3 0 c m deep
Net Weight
42 lbs 19 kg
Shipping Weight
49 lbs 22 kg
'See Installation section for amplifier p o w e r r e c o m m e n d a t i o n ,
N o t e : Unlike m a n y "theatre type" loudspeaker systems that e x h i b i t a rise in the
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m i d r a n g e region, the 4311 is a true m o n i t o r providing substantially the s a m e
sensitivity t h r o u g h the full range of audible frequencies. M e a s u r e d sensitivity
below 5 0 0 Hz or above 2 0 0 0 Hz may be considerably greater than that of
other systems with higher EIA sensitivity ratings.
S i n c e the major p o r t i o n of the energy r e p r o d u c e d by the low frequency l o u d -
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speaker lies below 8 0 0 Hz, this specification has been d e v e l o p e d by using a
test signal warbled f r o m 100 to 5 0 0 Hz, rather than the c o n v e n t i o n a l 1-kHz
sine wave test signal on w h i c h the EIA sensitivity is based.
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