JBL 123A Woofer
1970-1978
The 123A is the legendary 12" woofer that powered the iconic L100 Century - the best-selling speaker in JBL history. With its Alnico V magnet and distinctive white cone with 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 was developed from JBL's professional monitor lineage, specifically the 2213 woofer used in studio monitors. When JBL decided to create a consumer version of their successful 4310 studio monitor (which became the L100), the 123A was the natural choice for the woofer.
The combination of high sensitivity (91 dB), powerful Alnico magnet, and refined cone treatment made the 123A ideal for the dynamic, uncompressed sound that characterized the "West Coast Sound" - 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- Lansing Heritage - Comprehensive JBL specifications, photos, and historical documents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
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