JBL 4750A
The JBL 4750A is a professional-grade, high-power two-way loudspeaker system from JBL's Sound Power Series, built for touring and installation in discotheques and medium-to-large venues. It's a hefty cabinet at 60 kg and nearly a meter tall. It's designed to be stacked in wedge-shaped clusters, and each additional cabinet extends horizontal coverage by 30 degrees. The trapezoidal enclosure is there for coverage, not styling.
The low end is handled by a pair of 30 cm (12") 2206H cone woofers. The highs come from a 2445J compression driver with a 10 cm titanium diaphragm, mounted on a 2380A flat-front biradial horn. It's a bi-amplified system. The woofers run at 4 Ω with a 1,200W AES rating, and the horn section runs at 16 Ω with a 150W continuous program rating. The recommended crossover point is 1.2 kHz. Stated output sensitivity is 98 dB for the low section and 112 dB for the high section (2.83V/m), with maximum outputs of 129 dB and 133 dB respectively. Frequency response is rated at 32 Hz to 20 kHz (-10 dB). Input connections are two Neutrik NL8MPR speakON connectors.
There is no passive crossover inside the cabinet in the usual sense. The 4750A is meant to be driven actively, with an external electronic crossover - typically a JBL/UREI 5235 with the appropriate card set - splitting the signal before two amplifiers, one for the lows and one for the highs. Inside the enclosure, the compression driver is protected by a passive protection network only. A forum user in the JBL vintage community notes a recommended filtering range of 800 Hz to 1,200 Hz, though the manufacturer's spec calls for 1.2 kHz. Run one without the active crossover and you're asking for trouble. The small amount of owner discussion that exists centers on blown diaphragms, and one French forum user attributes the failures to diaphragms from the 1990s being filtered too low or an amplifier passing DC.
The original price in Japan was ¥470,000 per unit around 1992, which gives some sense of its professional positioning. Surviving documentation is thin otherwise — no production years are firmly established, and no period reviews from the audio press have surfaced. What the record does show is a capable, no-frills pro speaker that was also offered alongside sub-bass systems including the 4745A, 4748A, 4785A, and 4788A.
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