JBL 4728AP (circa 1992)
The JBL 4728AP is a two-way, bass-reflex stage monitor from JBL's Sound Power Series. It sold in Japan for ¥280,000 per unit around 1992. It's a low-profile wedge for foldback duty, with a dual-angle cabinet that gives you a 45° or 67.5° baffle angle when it's sitting on the floor. That's handy on a monitor. You can aim it at the performer's ears without propping it up on anything.
The woofer is a 30 cm (12") 2206H cone. The highs come from a horn-loaded compression driver, a 2426J with a pure titanium diaphragm, mated to the 2344A Bi-radial® horn. The crossover sits at 1.2 kHz. There's a tuning port in the back of the radial horn, which JBL said helped extend bass in the compact enclosure. It's rated for 600W (IEC 268-5, pink noise), produces 96 dB at 2.83V/m, and hits 123 dB max. Dispersion is 100° x 100° at -6 dB, wide enough to cover a performer who moves around. Impedance is 8 ohms. Connections are two Neutrik NL4MPR speakONs, so you can daisy-chain. It weighs 22 kg and measures 438 x 646 x 304 mm (W x H x D).
The Sound Power Series was JBL's professional install and portable PA line of the late '80s and early '90s. The 4728AP shows up in at least one documented bar installation alongside 4751 tops and 2445J compression drivers. A DIY audio forum member once singled it out as a notable horn/direct-radiating design and lumped it in with the respected 4430 and 4435 studio monitors. That's anecdotal. A GrabCAD model exists for the cabinet, though its creator admits the measurements "are not 100% correct." That's about the extent of the public record. No production years beyond the 1992 price reference, no period reviews, and no current market pricing have surfaced.
Known specs
- Type: 2-way, 2-speaker, bass reflex stage monitor
- Low band: 2206H 30 cm cone woofer
- High band: 2426J compression driver (titanium diaphragm) + 2344A Bi-radial® horn
- Frequency response: 60 Hz – 20 kHz (-10 dB)
- Sensitivity: 96 dB / 2.83V/m · Max SPL: 123 dB
- Power handling: 600W (IEC 268-5, pink noise)
- Crossover: 1.2 kHz
- Dispersion (-6 dB): 100° H x 100° V
- Impedance: 8 ohms
- Connectors: Neutrik NL4MPR x2
- Dimensions: 438 x 646 x 304 mm · Weight: 22 kg
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