3
Figure 5. Action of braking coil in Differential Drive
®
systems.
Figure 6. Cross-section view of MF driver in
LSR6332 system.
Figure 7. Cross-section view of HF driver in LSR6332
and LSR6328P systems.
half-roll surround is of butyl rubber. The transducer has
sufficient excursion capability and linearity to enable it
to be crossed over at 250 Hz, operating comfortably at
rated input power. It is free of the midrange distortion
that afflicts many similar drivers operating in the 250
Hz range at high levels.
The model 053TiS high frequency (HF) driver,
redesigned with magnetic shielding, is shown in Figure
7. It has a 25 mm (1 in) smooth titanium dome which
has been damped by a thin coating of Aquaplas
®
as
well as with a unique low recovery foam pad in the
rear cavity adjacent to the diaphragm. Its frequency
response extends smoothly beyond 20 kHz. When
mounted in both the LSR6332 and LSR6328P
systems, the HF driver is loaded by an elliptical oblate
spheroid waveguide that controls the driver’s
dispersion in the crossover range.
With the shielding of the HF driver (plus the inherent
shielding in the neodymium structures), the new
LSR6300 systems can be used in close proximity to
cathode ray type video monitors in all applications.
4. Detailed Performance of the LSR6332
System:
Overview of System:
Three-way passive with 300 mm (12 in) LF driver
Sensitivity: 90 dB SPL, 1 W input at 1 m (93 dB SPL,
2.83 Vrms input at 1 m)
Impedance: 4 ohms nominal
Nominal frequency response: 60 Hz
−
22 kHz,
+1 dB,
−
1.5 dB
Long term maximum power (IEC265-5): 200 W
continuous (113 dB SPL)
System dimensions (W
×
H
×
L): 635
×
394
×
292 mm
(25
×
15.5
×
11.5 in)
System weight: 20.4 kg (45 lb)
Integral M6 mounting points
In addition to the superlative directional response
shown in Section 2 of this Technical Note, the
LSR6332 excels as well in areas of distortion and in
time domain integrity. We now discuss these:
Response Uniformity:
Figure 8 shows the contribution of each transducer in
the system. Noteworthy here are the steep 24 dB/
octave transitions between sections and the in-phase
−
6 dB summation at each transition that are
characteristic of Linkwitz-Riley filter designs. The high
slopes between adjacent elements are crucial in
assuring smooth response throughout the target
listening windows. All network components in the
primary signal paths are of the highest quality,
including low loss capacitors and high saturation
current, low distortion inductors.
The system’s response has been so precisely adjusted
that JBL felt the only useful option for the user would
be a relatively small HF adjustment, as shown in
Figure 9. Here, you can see the effect of the
−
1 dB
jumper setting on the terminal block on the rear of the
enclosure. While this may look very small, bear in
mind that a one-dB adjustment over a range of about
three octaves is significant in terms of acoustical
power reduction. The user will normally opt for flat
response, the
−
1 dB option being called for when the
systems are used in rooms that have minimal
absorption at higher frequencies.
71800_JBL.TechNote
8/26/04, 7:58 AM
3
