JBL 2425J/2425H (c. 1983)
The JBL 2425J/2425H is a professional compression driver built for studio monitor and sound reinforcement duty. It was sold in Japan around 1983 at ¥82,000 per unit. The two model suffixes denote impedance variants only: the 2425J is the 16 Ω version, while the 2425H is typically 8 Ω (though one source lists it as 4 Ω). Everything else about the driver is shared.
The 2425 uses a 0.05 mm pure titanium diaphragm with a 4.4 cm aluminum voice coil. JBL used what it called a "diamond suspension", an original idea at the time, to extend the high-frequency range and improve linearity. The driver is rated from 800 Hz to 20 kHz with a sensitivity of 110 dB/W/m, and it handles 70 W continuous program. The magnetic flux density is a substantial 17,000 gauss. It measures 149 mm in diameter by 104 mm deep and weighs 4.8 kg.
The 2425 is part of a well-documented JBL family of 1-inch-throat compression drivers. The same diaphragm and voice coil assembly is shared with the 2420, 2421, 2426, and 2427, and replacement titanium diaphragms for all of these are still readily available from several aftermarket suppliers. On enthusiast forums, owners report pairing the 2425 with Altec 511b and JBL 2370 Bi-Radial horns, typically crossing over around 1 kHz. A common modification documented by hobbyists is coating the titanium diaphragm with Aquaplas. This is associated with JBL engineer Greg Timbers' philosophy that "if it's metal, coat it."
Surviving documentation on the 2425J/2425H is thin beyond its Japanese market listing. No official JBL datasheet surfaced in research, and there is no record of original US pricing or detailed production years beyond the circa-1983 date attached to the ¥82,000 price. The used market shows these drivers have held their value: pairs of 2425J units have been offered around $200, and used 2425H drivers have been listed at roughly $199 each. Aftermarket diaphragms, in both 8 Ω and 16 Ω versions, run around $60.
- Type: Compression driver (1-inch throat, 2.5 cm)
- Impedance: 2425J — 16 Ω; 2425H — 8 Ω
- Frequency range: 800 Hz – 20 kHz
- Recommended crossover: 800 Hz or above
- Input capacity: 70 W continuous program
- Sensitivity: 110 dB/W/m
- Diaphragm: 0.05 mm pure titanium, diamond suspension
- Voice coil: 4.4 cm aluminum
- Flux density: 17,000 gauss
- Dimensions: 149 mm dia. × 104 mm depth
- Weight: 4.8 kg
Japanese audio databases list the 2425J/2425H as a "wide range driver unit" suited for studio monitors and SR use. It is not a consumer speaker. You mount it on a horn and cross it over properly. Replacement diaphragms are still manufactured decades later.
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