JBL 2451H/2451J (1993)
The JBL 2451H/2451J is a professional high-frequency compression driver released in 1993. It was an early user of a neodymium magnet, where JBL's earlier drivers like the 2420 and 2441 used alnico and ferrite. The phase plug uses JBL's "Coherent Wave" structure and is designed to couple directly to the horn throat.
The driver is rated at 111 dB SPL (1W, 1m, measured in the 2 kHz octave band with a Q = 6.3 horn). It covers 500 Hz to 20 kHz at -10 dB, with a recommended minimum crossover of 500 Hz. Continuous program power handling is 100W above 500 Hz, rising to 150W above 1 kHz. Magnetic flux density is a strong 1.9T. Each unit measures 165mm in diameter by 73mm deep and weighs 4.5kg, which is light for a driver of this output class. The neodymium magnet is the reason. The original Japanese retail price was ¥208,950 (tax included) per unit, as listed around 2007.
The 2451H/2451J was used in JBL T 771 speakers with two 2227H 15" drivers. A Musician's Friend listing of the era described the result as "sparkling sound" and noted the driver's rugged construction for both fixed installations and touring. The same listing also mentioned JBL's rigid post-manufacture frequency response testing. The historical record is thin beyond that. The sources available to the Archive give no production end date, no detailed frequency response curves, and no documented common failure modes.
Known specifications:
- Throat diameter: 38mm
- Nominal impedance: 8 Ω (2451H) / 16 Ω (2451J)
- Diaphragm: 100mm pure titanium, diamond surround
- Voice coil: 100mm edge-wound aluminum ribbon
- Frequency range: 500 Hz – 20 kHz (−10 dB)
- Recommended minimum crossover: 500 Hz
- Power handling: 100W continuous (>500 Hz), 150W continuous (>1 kHz)
- Sensitivity: 111 dB SPL (1W/1m, 2 kHz octave band, Q=6.3 horn)
- Magnetic flux density: 1.9T (neodymium)
- Dimensions: 165mm dia. × 73mm deep
- Weight: 4.5kg
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