Developed to meet the challenge of digital and advanced analog recording technology, the JBL Model 4430 {and Model 4435} represent a significant new approach to two-way studio monitor design. The incorporation of the unique JBL Bi-Radial ™ horn in a monitor loudspeaker provides constant vertical and horizontal polar coverage, control of the reverberant field, flat power response, image stability, and coherent sound. The two models also feature improvements in compression driver, low frequency transducer, and dividing network technology. Both systems exhibit the traditional )BL attributes of wide bandwidth, smooth frequency response, high efficiency, wide dynamic range, and exceptional reliability.
The practical benefits of the Bi-Radial monitors include stable stereo imaging that remains fixed over a wide range of horizontal positions, the result of unusually smooth off-axis response. The design allows considerable latitude in physical placement. The wide vertical response, identical to the horizontal, includes both standing and seated listeners within the coverage angle, even in proximity to the monitors.
THE JBL BI-RADIAL ™ HORN
The Models 4430 offer performance levels normally achieved by three- and four-way systems. The key to this performance is the JBL Bi-Radial ™ horn 1 and its integration in a monitor design.
Most horn designs compensate for the failing power response of the compression driver with directivity that increases with frequency. This provides flat axial response, but power response that typically falls by 6 dB per octave from as low as 3 kHz. The resulting decrease in coverage angle (as the frequency increases) gives generally poor control of the reverberant field and (in two-way designs) is not well matched to the coverage angle of the low frequency driver at the crossover frequency. By contrast, the JBL Bi-Radial ™ horn provides constant coverage over its operating bandwidth. Both on-axis and off-axis pressure response are flat, and the vertical coverage angle is identical to the horizontal. This angle is wide, 100° x 100°, but very tightly controlled, and it matches the coverage angle of the low frequency driver at the crossover frequency. Additionally, the horn's rapid flare rate reduces second harmonic distortion, and its reduced depth puts its driver in the same acoustic plane as the low frequency driver. The Bi-Radial ™ monitors present a coherent sound source, with extremely stable stereo imaging over a wide variety of listening positions. The monitors offer a high degree of placement flexibility, and the listening position can be quite close with no loss of stereo imaging.
Equalization of the 4430 will typically be needed only to correct for inherent room anomalies rather than for monitor response. This is the result of uniform frequency response within the coverage angle. The controlled power and polar response of the JBL Bi-Radial ™ monitors effectively removes them from the variables with which a recording engineer must contend.
HIGH FREQUENCY COMPRESSION DRIVER
The Bi-Radial ™ horn is coupled to a compression driver which is crossed over at I 000 Hz. The driver features a titanium diaphragm with a three-dimensional diamond-pattern suspension . Developed by JBL, this diamond surround offers an extended frequency response normally associated with exotic materials while retaining ruggedness and high power capacity. The diaphragm is pneumatically drawn to shape to eliminate stresses that cause fatigue, and a phasing plug of concentric exponential horns eliminates phase cancellation.
LOW FREQUENCY
The low frequency loudspeakers used in the Bi-Radial ™l monitors incorporate the latest technology to deliver smooth response, extended bandwidth, and extremely low distortion. The magnetic structures feature JBL's Symmetrical Field Geometry (SFGI design to reduce second harmonic distortion to inconsequential levels. New adhesives technology and coil former construction improve power handling. The coil itself, 100 mm (4 in) in diameter, is fabricated from edge-wound copper ribbon, and operates in a magnetic field having a flux density of 1.2 T (12,000 gauss). The 19 mm(% in) length of the voice coil allows increased linear excursion, and a careful choice of suspension elements helps to completely eliminate dynamic instabilities.
The 4430 differ chiefly in their low frequency capabilities. The 4430 uses a single 380 mm ( 15 in) low frequency driver and is 3 dB down at 32 Hz; it can handle full power input to 27 Hz. The system is down 3 dB at 27 Hz and will handle full power down to 22 Hz. The systems use similar low frequency drivers, but the cone assemblies.
FREQUENCY DIVIDING NETWORK
The frequency dividing network of the Bi-Radial ™ monitors has a crossover frequency of I kHz and a nominal slope of 12 dB per octave. The cut-off slope and shape were chosen to provide the smoothest possible response over the widest bandwidth, restricting any off-axis anomalies to a very narrow portion. JBL has paid considerable attention to both the off-axis response and the total power response, and the network optimizes these parameters. While
the response is smooth at all angles, the flattest response is, by design, on-axis and above. This offers a greater number of listening positions when the system is mounted at or below ear level; for mounting above ear level, the system can be inverted to offer the same advantages. The network also provides equalization of the compression driver. Because the power response of the driver and the Bi-Radial ™ horn is greater in the midrange than at high frequencies, this equalization attenuates the lower end of the compression driver's response, lowering distortion and giving greater dynamic headroom. The equalization is provided in two stages, allowing separate adjustments (via front panel level controls) for the midrange and high frequencies.
A switch located adjacent to the connection terminals allows the monitor to be bi-amplified. A special crossover card is available for the IBL Model 5234A electronic frequency dividing network to provide the appropriate crossover characteristics.
Specifications
Frequency Response: 35 Hz - 16,000 kHz ±3 dB
Sensitivity: 93 dB SPL
Efficiency: 1,3%
Dispersion Angle
Horizontal : 100° (+10°; -30°)
Vertical : 100° (+0°, -30°)
Impedance: 8 Ω nominal
Max. Power Input: 300 W
Continuous Sound Pressure Level: 119 dB
Crossover Frequency: 1,000 Hz
Driver Complement:
Low Frequency : 2235H
Compression Driver : 2425H
Horn : 2344
Enclosure Volume: 0,14m³ (5 cu. Ft)
Resonance Frequency: 34 Hz
Dimensions: 908 x 556 x 400 mm (480 mm deep w/horn)
Weight Net: 26 kg (57 lbs)