JBL L40
1978 - 1982
The L40 was a refined 2-way bookshelf speaker designed to reproduce any genre of music with accuracy and musicality. It featured JBL's first use of a glass wool shell behind the woofer to improve impedance characteristics, along with the company's first dome tweeter in this price class.
Specifications
| Type | 2-way, 2-speaker, Bass Reflex, Bookshelf |
|---|---|
| Drivers | Woofer: 10" 127A, Tweeter: 033 Dome |
| Crossover Frequency | 1.8 kHz |
| Nominal Impedance | 8 Ω |
| Power Handling | 35W (continuous program) |
| Sensitivity | 88 dB/W/m |
| Frequency Response | 50 Hz - 20 kHz |
| Dimensions | 381 x 584 x 302 mm (W x H x D) |
| Weight | 20 kg (per speaker) |
Drivers Used
- Woofer: 127A - 10" (25cm) cone woofer with unique ribbed corn paper and 5cm copper ribbon edgewise wound voice coil
- Tweeter: 033 - 2.5cm (1") dome tweeter with phenol-treated diaphragm and 14,000 Gauss magnetic circuit
Innovative Features
The L40 introduced several technologies that were advanced for its class:
- Glass Wool Shell: A JBL-developed basket-shaped glass wool shell covered the back of the woofer, acting as damping to flatten impedance characteristics without restricting cone movement
- Center Dome: The 127A woofer featured a 10cm diameter center dome to improve mid and high-frequency characteristics and directional response
- 033 Dome Tweeter: Used phenol-treated hard diaphragm with aluminum ribbon wire edgewise winding for faithful reproduction beyond the audible range
- Variable HF Control: Continuously adjustable level control for the tweeter to match room acoustics and personal preference
- Aluminum Die-Cast Frame: Suppressed unwanted resonance on the woofer
Professional-Grade Network
The crossover network was designed based on professional studio monitor circuits, using:
- Low-loss inductors
- High-voltage capacitors with excellent characteristics
- High-precision coils and resistors
Variants
- L40 (1978-1982): Original version with walnut finish
- L40A: Updated variant with minor refinements
- Grille Colors: Brown, red, and camel options available
Historical Context
The L40 represented a new direction for JBL's smaller speakers, incorporating dome tweeter technology previously reserved for higher-end models. The 033 tweeter's small-diameter dome provided significantly improved directional characteristics compared to cone tweeters, allowing more flexible placement while maintaining high-frequency response.
The glass wool shell behind the woofer was a particularly innovative solution to impedance correction, demonstrating JBL's commitment to engineering excellence even in affordable models. This approach would influence future JBL designs.
Related Models
The L40 was positioned between the smaller L26 and the 3-way L36 Decade. Its 033 tweeter would later appear in the L150 and other premium models.
Documentation
No specific datasheet available in archive. See JBL Loudspeaker Components 1979 Catalog for related information.