LSR28P
Linear Spatial Reference
Bi-Amplified Monitor System
Key Features:
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Linear Spatial Reference design
based on spatial response
measurements and psychoacoustic
principles.
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Differential Drive®Technology with
dynamic braking for extended low
frequency response and low power
compression.
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Integrated Bi-amplification with calibrated and variable sensitivities.
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Titanium Composite High Frequency Device with Elliptical Oblate
Spheroidal Waveguide and
Damped Pole Piece.
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Carbon Fiber Composite Baffle for
low cabinet resonance and stable
inertial ground.
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Linear Dynamics Aperture Port
Design eliminates port noise and
reduces port compression.
The LSR28P Linear Spatial Reference Studio Monitor combines JBL’s
latest in transducer and system technology with recent breakthroughs in
psychoacoustic research to provide a
more accurate studio reference.
The Linear Spatial Reference (LSR)
philosophy is based on a set of
design goals that carefully control the
overall performance of the system in
a variety of acoustic spaces. Instead
of focusing on a simple measure such
as on-axis frequency response, LSR
designs require much better control
over dispersion via transducer selection and crossover frequency design.
Critical decisions of image placement,
EQ, balance and timbre are typically
made within +/- 15° vertically and
+/- 30° horizontally. This workspace
is where the engineer, producer and
artist make critical mixing decisions
and this is the area that LSR is optimized for superb in room response.
By incorporating LSR into the system
design requirements, placement rules
are relaxed, a more stable stereo
image is maintained and off-axis coloration is minimized.
218F Low Frequency Transducer:
The 8” woofer is based on JBL’s patented Differential Drive technology. With dual 1.5” drive coils, power compression is kept to a minimum to reduce spectral shift as power levels increase. An added third
coil between the drive coils acts as a dynamic brake to limit excess
excursion and reduces audible distortion at maximum levels. The cone
is made of a carbon fiber composite forming a rigid piston and is supported by a soft butyl rubber surround.
053ti High Frequency Transducer:
The high frequency device is a 1" composite diaphragm integrated
with an Elliptical Oblate Spheroidal (EOS) Waveguide with 60 x 100
degree dispersion which is critical to the smooth spatial response
required in today’s working environments.
Amplitude and Phase
䉴 LSR28P Linear Spatial Reference Bi-Amplified Monitor System
1. On-Axis Response
2. Spatially Averaged Response
over a range of +/- 30° Horizontal & +/- 15° Vertical
3. First Reflection Sound Power
4. Total Radiated Sound Power
5. DI of On-Axis Response
6. DI of First Reflections
LSR Measurement Techniques:
LSR is the underlying design philosophy that
explains why speakers that measure the same,
sound different. By going beyond simple on-axis
frequency measurement, LSR techniques define the
ultimate performance specifications of our monitoring technology—what it will sound like in your
room. We go beyond the performance of an on-axis
frequency response at one point in space, which
other manufacturers use.
LSR uses a technique of measuring a monitor
over a sphere that encompasses all energy radiated
into the listening room in every direction. This data
reflects 1296 times the information of a single on-axis
frequency response curve. Using psychoacoustic principles allows the calculation and optimization of the
entire sound field heard by the listener - this includes
the direct sound field, the reflected sound field and the
reverberant sound field. In place of spectral smoothing,
which actually conceals data, LSR techniques expose
flaws in systems such as resonances, poor dispersion
and other off-axis colorations.
The LSR graphic below is a set of Spatially Measured
graphs that are at the heart of the LSR philosophy. 1296
times the information of a single on-axis
Bi-Amplified Power System:
The LSR28P combines two high power amplifiers
with an active crossover system which includes
over 250 watts of continuous low frequency power
and 120 watts for the high frequency. Active
crossover circuitry results in a 36 dB/Octave
Linkwitz-Riley Electroacoustic response between
low and high frequency devices for smooth transition in both the frequency and time domains. This
results in exception imaging and a lack of time
smear.
User adjustments include level calibration for setting with professional and semiprofessional equipment as well as fine tuning of levels with variable
level trim. XLR and 1/4” input connection can be
accommodated as well as balanced and unbalanced
signals.
+2 dB
Flat
-2 dB
+2 dB
Flat
-2 dB
36 dB/Octave
24 dB/Octave
User Adjustments
LSR28P Response Curves
The frequency response of bass and treble amplitudes
can also be adjusted to compensate for placement and
room absorption characteristics. The graph below outlines the various response options.
ON
115V
Specifications:
System:
Frequency Response (+1, -1.5 dB)2: 50 Hz - 20 kHz
Enclosure resonance frequency: 38 Hz
Low Frequency Extension: User controls set to default
-3 dB: 46 Hz
-10 dB: 36 Hz
Low - High Frequency Crossover: 1.7 kHz
6th-Order Acoustic Linkwitz-Riley
Distortion, 96 dB SPL, 1m:
Mid-High Frequency (120 Hz - 20 kHz):
2nd Harmonic: <0.6%
3rd Harmonic: <0.5%
Low Frequency (<120 Hz):
2nd Harmonic: <2%
3rd Harmonic: <1%
Maximum SPL (80 Hz - 20 kHz): >108 dB SPL / 1 m
Maximum Peak SPL (80 Hz - 20 kHz): >111 dB SPL / 1 m
Signal Input: XLR, Balanced
1/4” Tip-Ring-Sleeve, Balanced
Positive voltage applied to XLR Pin 2 (1/4” Tip)
produces outward woofer motion.
Calibrated Input Sensitivity:
XLR, +4 dBu: 96 dB/1 m
1/4”, -10 dBV: 96 dB/1 m
AC Input Voltage: 115/230 VAC, 50/60 Hz (User Selectable)
AC Input Voltage Operating Range: +/- 15%
AC Input Connector: IEC
Long Term Maximum System Power: 220 Watts (IEC265-5)
Self Generated Noise Level: <10 dBA SPL/1 m
User Controls:
High Frequency Control (2 kHz - 20 kHz):
+2 dB, 0 dB, -2 dB
Low Frequency Control (<100 Hz) +2 dB, 0 dB, -2 dB
Low Frequency Alignments: 36 dB/octave, 24 dB/Octave
Calibrated Input Attenuation: 5 dB, 10 dB
Variable Input Attenuation: 0 - 13 dB
Transducers:
Low Frequency Model: 218F
Diameter: 203 mm (8 in.)
Voice Coil: 38 mm (1.5 in.) Differential Drive
with Dynamic Braking Coil
Magnet Type: Ferrite with Integral heat sink
Cone Type: Carbon Fiber Composite
Impedance: 2 ohm
High Frequency Model: 053ti
Diameter: 25 mm (1 in.) diaphragm
Voice Coil: 25 mm (1 in.)
Magnet Type: Ferrite
Diaphragm Type: Damped Titanium Composite
Other Features: Elliptical Oblate Spheroidal Waveguide
Impedance: 4 ohms
Amplifier:
Low Frequency:
Topology: Class A-B, All Discrete
Sine Wave Power Rating: 250 Watts (<0.1% THD into rated impedance)
THD+N, 1/2 power: <0.05%
High Frequency:
Topology: Class A-B, Monolithic
Sine Wave Power Rating: 120 watts (<0.1% THD into rated impedance)
THD+N, 1/2 power: <0.05%
Physical:
Finish: Black, Low-Gloss, “Sand Texture”
Enclosure Volume (net): 50 liter (1.0 cu. ft.)
Low Frequency Vent: Rear Ported Linear Dynamics Aperture
(Integrated with Amplifier heat sink)
Baffle Construction: Carbon Fiber Composite
Cabinet Construction: 19 mm (3/4” M.D.F.)
Net Weight: 22.7 kg (50 lbs)
Dimensions (WxHxD): 406 x 330 x 325 mm (16 x 13 x 12.75 in.)
Notes:
All measurements unless otherwise stated made anechoically in a 4π environment at 2
meters and referenced to 1 meter by the inverse square law.
The reference measurement microphone position is located perpendicular to the centerline of the low and high frequency transducers, at the point 55 mm (2.2 in.) below
the center of the tweeter diaphragm.
Acoustic loading provided by the listening room increases Maximum SPL capabilities
and Low Frequency Bass Extension as compared to stated anechoic values.
Distortion measurements performed with the input voltage necessary to produce the
stated “A” weighted SPL level at the stated measurement distance. Distortion figures
refer to the maximum distortion measured in any 1/10th octave wide band in the stated frequency range.
JBL continually engages in research related to produce 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.
䉴 LSR28P Linear Spatial Reference Bi-Amplified Studio Monitor System
JBL Professional
8500 Balboa Boulevard, P.O. Box 2200
Northridge, California 91329 U.S.A.
A Harman International Company
SS LSR28P
CRP 10M
3/99
Impulse Response Acoustic Contribution
96 dB/1 m (Distortion raised 20 dB)
102 dB/1 m (Distortion raised 20 dB)
2nd
3rd
2nd
3rd
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