JBL 124H (c. 1981)
The JBL 124H is a 30 cm cone woofer from JBL's Loudspeaker Component Series. That means JBL never built it into a complete consumer speaker cabinet. It was offered as a raw driver for DIY builders and system designers. It appears to have been sold around 1981, at a Japanese retail price of ¥53,000 per unit. A 26-page user manual exists, though the archive doesn't document its contents well.
The record on the driver itself: a 10.2 cm voice coil, a magnetic flux density of 12,000 gauss, and a rating of 200W continuous program power. Frequency response is specified from 25 Hz to 2 kHz, with a free-air resonance (fo) of 16 Hz. Sensitivity is 91 dB/W/m and nominal impedance is 8 ohms. JBL recommended enclosure volumes of 42 to 85 liters. The driver is 121 mm deep and weighs 10.4 kg packed.
The 124H has a "mass control ring," which JBL said extended the playback band into the ultra-low frequencies while improving low-distortion characteristics. JBL described it as having the same characteristics and sound quality as a studio monitor woofer. A forum discussion on audioheritage.org suggests it may be the consumer version of the professional 2203H, though this is unconfirmed. The same thread includes someone wondering why JBL would make a model that never appeared in a consumer speaker.
A September 2025 sale at a Japanese dealer (afroaudio.jp) shows current condition and value. The unit sold for ¥20,000, graded B-rank, with confirmed operation, no accessories, no original box, unknown maintenance and owner history, and a 90-day dealer warranty. The gasket showed many small holes from age, and there were small scratches and scuffs in places.
Known specifications:
- Type: 30 cm cone woofer
- Impedance: 8 ohms
- Allowable input (continuous program): 200W
- Sound pressure level: 91 dB/W/m
- Frequency response: 25 Hz – 2 kHz
- fo: 16 Hz
- Voice coil diameter: 10.2 cm
- Magnetic flux density: 12,000 gauss
- Recommended enclosure volume: 42 – 85 liters
- Depth: 121 mm
- Weight (packed): 10.4 kg
Missing from the record: production years (only the approximate 1981 pricing date), overall dimensions besides depth, crossover data, and any reliable owner reviews. The manual's amplifier recommendations — up to 75W continuous sine wave per channel for systems rated under 50W program, and up to 150W for those rated higher — come from the manual itself and are worth noting for anyone driving these with a modern amp. Beyond that, the 124H remains a fairly obscure JBL component, better documented in Japanese sources than American ones, and likely best known today among DIY enthusiasts hunting for a capable 12-inch woofer.
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