JBL 4756A (c. 1992)

The JBL 4756A is a professional tri-amplified loudspeaker system built for sound reinforcement in medium-to-large halls. It was sold in Japan around 1992 at ¥580,000 per unit. It is one of the less-documented entries in JBL's professional catalog. Most of what's known comes from a single Japanese spec database, with little independent corroboration.

The 4756A is a 3-way, 5-speaker bass-reflex design built from JBL's professional drivers. Two 30-cm (12-inch) 2206H cone woofers handle the low end. The midrange is a horn-loaded compression driver, the 2445J with a 10-cm titanium diaphragm, mated to a flat-front biradial 2380A horn with a 5-cm throat. A pair of 2404H biradial ring radiators takes the high frequencies. Two woofers, one mid horn and two high-frequency units make five speakers.

This is install-grade gear. The recommended crossover points are 1.2 kHz and 7 kHz, and the system is meant to be tri-amplified, with separate inputs for low (4 Ω, 1,200W AES), mid (16 Ω, 150W program) and high (16 Ω, 40W program) bands. A crossover network, the N4751AP, could be inserted between mid and high to convert it to a bi-amplified setup. Connection is via Neutrik NL8MPR speakON connectors. The cabinet measures 850 × 680 × 480 mm and weighs 65 kg (per audio-database.com; a YouTube listing claims 130 kg, likely per pair).

Playback band is 32 Hz to 20 kHz (-10 dB). Output sensitivity is 98 dB (low), 112 dB (mid) and 105 dB (high) at 2.83V/m. Maximum SPL is 129 dB, 133 dB and 124 dB respectively. The directional characteristic is rated at 90° horizontal by 40° vertical (-6 dB).

The 4756A is a derivative of the earlier 4755A - essentially that model with the pair of 2404H ring radiators added for extended high-frequency coverage. Past that, the record thins out. No period reviews have surfaced, no production run dates beyond the approximate 1992 price reference, and no service documentation has been found. A couple of European used-gear listings from the 2020s ask €1,950 per pair, so it still circulates on the secondhand market.

Known specs, in brief: