The low frequency
transducer shall have a nominal diameter of 460 mm (18in), overall
depth not greater than 191 mm (7 1/2 in) and weigh at least 13.6 kg
(30 lb). The frame shall be of cast aluminum to resist deformation,
and the magnetic assembly shall utilize a ferrite magnet and produce
a symmetrical magnetic field at the voice coil gap. In addition, a
Flux Stabilizing Ring encircling the pole piece shall act to reduce
flux modulation. The voice coil shall be 100 mm (4 in) in diameter
and shall be made of edgewound copper ribbon operating in a magnetic
field of not less than 1.22 T (12,200 gauss).
of a typical production unit shall be as follows: Measured sensitivity
(SPL at 1 m (3.3 ft) with 1 W input, swept 100 Hz to 500 Hz) shall
be at least 95 dB on axis. As an indication of electromechanical conversion
efficiency, the B1 factor shall be at least 21 newtons per ampere.
The half-space reference efficiency shall be 2.1%. Usable frequency
response shall extend from 20 Hz to 2 kHz. On-axis response, measured
at a distance of 2 m (6.6 ft) or more under free field conditions,
shall be ± 3 dB from 40 Hz to 800 Hz. Acoustic loading shall further
extend the low frequency response. Nominal impedance shall be 8 ohms.Rated
power capacity shall be at least 600 W normal program material.
shall be the JBL Model 2245H. Other loudspeakers will be considered
for equivalency provided that submitted data from a recognized independent
test laboratory verify that the above performance specifications are
engages in research related to product improvement. New materials,
production methods, and design refinements are introduced into existing
products without notice as a routine expression of that philosophy.
For this reason, any current JBL product may differ in some respect
from its published description, but will always equal or exceed the
original design specifications unless otherwise stated.