The JBL 2122H is a 25 cm cone mid-woofer built for the middle and low range of four-way systems. It is best known as the dedicated mid-bass driver in JBL's large-format studio monitors, the 4344 and 4345. In those systems it handles the transition region between the deep bass woofers and the horn-loaded midrange.
What makes the 2122H interesting is its engineering. JBL designed it with a free-air resonance (fo) of just 35 Hz, which allowed it to produce extended low-frequency output from a relatively small sealed back cavity — a design choice that also prevented interference from the other drivers in the multi-way monitor cabinets. The impedance rise is small, enabling accurate crossover behavior even at low frequencies, and break-up distortion outside its operating band is extremely low. The driver uses a 75 mm copper ribbon voice coil and JBL's SFG (Symmetrical Field Geometry) magnetic circuit. It was rated at 8 ohms, with a 95 dB/W/m sensitivity, a usable frequency band of 250 Hz to 2 kHz, and a continuous program power handling of 75W.
One spec to note: the fact sheet lists both fo (35 Hz) and fs (40 Hz) as distinct values. The voice coil winding length on the original was .170 inches, which gives roughly 2 mm of linear travel each way. That is modest, and fits a mid-bass driver rather than a deep-bass woofer.
Documentation on the 2122H as a standalone product is thin. No production years, no USD pricing, and no period reviews have surfaced. It was priced at ¥56,000 per unit around 1983 in Japan. It remains a sought-after component, primarily because the 4344 and 4345 monitors are still highly regarded. Both foam surround refoam kits and full recone kits (including a genuine JBL C8R2122H kit) are readily available, which suggests foam surround deterioration is the expected failure mode with age.
Owners on audio forums have noted that aftermarket recone kits don't perfectly replicate the original's .170-inch voice coil. Some aftermarket kits use a .290 or .400 coil, which changes the linear excursion characteristics. It is worth asking what voice coil a recone kit includes before buying.
- Type: 25 cm cone mid-woofer (10″)
- Impedance: 8 Ω
- Sensitivity: 95 dB/W/m
- Frequency band: 250 Hz – 2 kHz
- fo: 35 Hz | fs: 40 Hz
- Power handling: 75W continuous program
- Magnet: 10,500 Gauss, SFG circuit
- Dimensions: 260 mm dia. × 113 mm depth
- Weight: 5.5 kg
- Enclosure volume: 11.3 L minimum
- Used in: JBL 4344, JBL 4345
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