JBL 123A Woofer
1970-1978
The 123A is the 12" woofer that powered the L100 Century, the best-selling speaker in JBL history. It has an Alnico V magnet and a white cone with the aqua-pus treatment. It defined the "West Coast Sound" of the 1970s.
Specifications
| Nominal Diameter | 12" (30cm) |
|---|---|
| Magnet Type | Alnico V |
| Voice Coil | 3" (75mm) edgewound aluminum ribbon |
| Cone Material | Paper with aqua-pus coating |
| Surround | Accordion fabric |
| Impedance | 8 Ω |
| Power Handling | 50W continuous |
| Frequency Response | 45 Hz - 2.5 kHz |
| Sensitivity | 91 dB/W/m |
| Magnetic Flux Density | 1.2 Tesla |
| Weight | 6.8 kg |
Key Features
- Alnico V Magnet: Premium aluminum-nickel-cobalt magnet for exceptional transient response and flux stability
- Edgewound Voice Coil: Aluminum ribbon wound on edge for improved heat dissipation and power handling
- Aqua-Pus Coating: Proprietary cone treatment for optimal mass and rigidity
- Accordion Surround: Fabric surround provides controlled compliance and long-term durability
- Cast Aluminum Frame: Rigid frame construction minimizes resonances
Applications
- L100 Century (1970-1978)
- 4310 Studio Monitor
- 4311 Studio Monitor
Historical Context
The 123A came out of JBL's professional monitor line, specifically the 2213 woofer used in studio monitors. JBL wanted a consumer version of its successful 4310 studio monitor, which became the L100. The 123A was the natural choice for the woofer.
The 123A has high sensitivity (91 dB), a powerful Alnico magnet and a refined cone treatment. That combination gave the dynamic, uncompressed sound of the "West Coast Sound". This was a sonic signature that emphasized transient accuracy and low distortion over the more colored sound of East Coast competitors.
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Documentation
- Lansing Heritage - Comprehensive JBL specifications, photos, and historical documents
- HiFi Engine - JBL manuals, service documents, and brochures
- Audio Karma JBL Forum - Community discussions and restoration guides