JBL 4742A (circa 1990–1992)

The JBL 4742A is a professional sub-bass loudspeaker system from JBL's Sound Power series. It uses a pair of 30 cm (12″) 2206H cone woofers in a bass-reflex, floor-standing enclosure. A period catalog calls it a "direct radiator sub-bass loudspeaker system," built to extend the low-frequency output of the full-range Sound Power systems - the 4716A, 4726AP, and 4728AP. JBL's own materials explained the thinking. Hand the energy-heavy low end to a dedicated sub-bass cabinet, and the full-range system gains headroom and the whole setup can take more input without strain. It was aimed at spaces needing serious SPL - discos, clubs, and installations where placement options were tight.

The specs are those of a serious PA sub. Rated impedance is 4 ohms, with an output sensitivity of 101 dB/2.83V/m and a maximum output of 129 dB. AES allowable input is 1,200W (60 Hz - 600 Hz), with a frequency characteristic of 35 Hz to 2.8 kHz at -10 dB. The crossover is variable from 80 Hz to 250 Hz, with a 30 Hz low cut and a stated maximum crossover frequency of 1.2 kHz. Input and output are via dual Neutrik NL4MP Speakon connectors. The cabinet measures 850 × 500 × 480 mm and weighs 46 kg. The original price in Japan was ¥270,000 per unit, circa 1992.

The brochure described the finish as "rugged and attractive." Beyond that, the written record is thin. No production years are documented beyond the circa-1992 price reference and a 1990 catalog date, and no professional reviews or owner impressions have surfaced. A forum user on freespeakerplans.com noted that exploded views and technical specs from JBL's vintage site were "alas… the only information i have been able to find so far." The 2206H driver is listed as re-coneable by at least one repair service, so the woofers can be serviced when they wear out.

Type: 1-way, 2-speaker, bass-reflex, floor-standing sub-bass system
Drivers: Two 30 cm (12″) JBL 2206H cone woofers
Frequency characteristic: 35 Hz – 2.8 kHz (−10 dB)
Output SPL: 101 dB/2.83V/m · Max: 129 dB
Allowable input (AES): 1,200W (60 Hz – 600 Hz)
Crossover: 80 Hz – 250 Hz variable, 30 Hz low cut (max 1.2 kHz)
Impedance: 4 ohms
Connectors: Neutrik NL4MP Speakon ×2
Dimensions: 850 × 500 × 480 mm · Weight: 46 kg
Original price: ¥270,000 (1 unit, circa 1992)