JBL 4785A (c. 1992)
The JBL 4785A is a professional sub-bass cabinet from JBL's Sound Power series. It is a floor-standing, dual-15″ bandpass subwoofer. The record on this model is thin, but what's documented points to a large-format touring and installation box built for output.
The enclosure uses JBL's Triple Chamber Bandpass (TCB) method. It loads two 38 cm (15″) 2225H woofers and has a rated frequency characteristic of 25 Hz to 250 Hz (−10 dB). Sensitivity is listed at 103 dB / 2.83 V / m, maximum output is 129 dB, and allowable continuous program input is 800 watts. Nominal impedance is 4 ohms. The crossover region is cited as 80-100 Hz, with a 30 Hz low cut. The enclosure is tuned at 35 Hz and 83 Hz. Dual tuning is typical of bandpass designs, which trade some efficiency for extended low-end control.
It's a big cabinet: 1,250 mm wide, 750 mm high and 519 mm deep, weighing 76 kg. Input and output connections are via two Neutrik NL8MPR speakON connectors. The original price was ¥430,000 per unit, referenced around 1992.
A period brochure survives (dated 1990). It describes the box as a "Dual 380 mm (15 in) Triple Chamber Bandpass Sub-Bass System," and the official spec sheet positions it for large halls and outdoor stages. Beyond that, the record is mostly quiet. A German forum thread from January 2004 shows a user who was offered four units cheaply and noted how little information was available online. One forum poster doubted JBL's low-frequency claims for a 15″ driver. That is a fair reaction to any bandpass design's numbers, but the official spec is the authoritative figure.
No production years, service history, or current collector pricing have surfaced. The 4785A is a known quantity among PA veterans, but it never generated the kind of documentation that JBL's studio monitors did.
- Type: 1-way, 2-speaker, TCB (Triple Chamber Bandpass), floor type
- Drivers: Two 38 cm (15″) 2225H cone woofers
- Frequency range: 25 Hz – 250 Hz (−10 dB)
- Sensitivity: 103 dB / 2.83 V / m; 129 dB max
- Power handling: 800 W continuous program
- Impedance: 4 Ω
- Connectors: Neutrik NL8MPR ×2
- Dimensions: 1,250 W × 750 H × 519 D mm
- Weight: 76 kg
- Original price: ¥430,000 (per unit, c. 1992)
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