JBL 2403H
The JBL 2403H is a ring-radiator super tweeter. It is best known as the top-end driver in JBL's professional studio monitors of the 1970s, specifically the 4333 and 4343 systems. It doesn't use a conventional dome or cone. It has a flat annular diaphragm driven by a voice coil, mounted in a small cast-aluminum housing. Think of it as a smaller, high-frequency-only relative of the 2402H slot tweeter, with the ring radiator approach in place of the slot-loading horn.
What's documented about its performance comes mostly from rebuild-service listings and owner reports, not factory datasheets. The commonly cited figures are a frequency response of 4,000-21,000 Hz, 8-ohm impedance, and 20W maximum power handling with a crossover. It is not a driver to run full-range. The recommended crossover range is roughly 6k-12kHz at 12dB/octave, and owners consistently note that it works best above 8kHz. The voice coil is 25mm aluminum, and sensitivity is listed around 105dB @ 1W/1m.
Owners describe the 2403H as smooth and free of harshness, an extension of the top end rather than a piercing add-on. The flip side, as one user put it, is that the driver is quite directional. You need to be in the sweet spot to get the benefit. Recording Engineer (December 1982, p.90) documented a professional installation using 2403H tweeters alongside 2225H woofers and a 2397 Smith horn with 2441 driver in bi-amped monitor cabinets.
Production years, original pricing, and physical dimensions are not documented in the available record. What survives is the driver itself, often found in pairs on the used market, with intact foam surrounds and diaphragms.
- Type: Ring-radiator super tweeter
- Frequency response: 4,000–21,000 Hz
- Impedance: 8 ohms
- Power: 20W max (with crossover)
- Crossover: 6k–12kHz, 12dB/octave recommended
- Voice coil: 25mm aluminum
- Sensitivity: 105dB @ 1W/1m
- Used in: JBL 4333 and 4343 studio monitors
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