JBL 2420 Compression Driver
The JBL 2420 is a professional 2-inch throat compression driver. It became a staple of JBL's horn-loaded studio monitors and cinema systems. It is known for its reliability and its classic "West Coast" horn sound, and it has proven exceptionally durable. Plenty of them still work in restored vintage systems today.
Specifications
| Type | Compression Driver (2-inch throat) |
|---|---|
| Diaphragm | 3-inch aluminum |
| Magnet | Alnico V |
| Voice Coil Diameter | 2 inches (50.8 mm) |
| Nominal Impedance | 8 Ω or 16 Ω |
| Power Handling | 50W continuous program |
| Frequency Response | 500 Hz - 15 kHz |
| Sensitivity | 112 dB/W/m (on appropriate horn) |
| Throat Diameter | 2 inches (50.8 mm) |
Applications
JBL used the 2420 widely in its professional lineup, including:
- Studio monitors (4343, 4344, 4350, 4355 series)
- Cinema speakers
- Sound reinforcement systems
- Custom horn-loaded installations
The driver was typically paired with JBL's 2307/2308 bi-radial horn or similar constant-directivity horns. That gave wide, even coverage in professional applications.
In the Wild
Featured in Resistor Magazine's restoration profile of Iwan Arjanto's vintage JBL collection. Arjanto is a restoration craftsman based in Indonesia. He specifically notes that the horn and tweeter assemblies in vintage JBL studio monitors - including the 2420 compression driver and 2405 slot tweeter - are essentially unbreakable.
"Vintage studio monitor speakers are more solid than JBL L100, but the horn and tweeter assemblies are unbreakable (JBL 2420 and 2405)."
— Iwan Arjanto
That durability is a key reason vintage JBL studio monitors remain restorable decades after manufacture. Cabinets may give way to humidity and time, but the compression drivers and tweeters often need only cleaning and minor service to work fully again.
Variants
- 2420: Original Alnico V version
- 2420A: Later version with potentially updated diaphragm mounting
- 2421: Evolution with improved phase plug design
- 2425: Later titanium diaphragm version with similar form factor
Maintenance & Restoration
The 2420's Alnico magnet structure is extremely stable and rarely requires recharging. Common restoration needs include:
- Diaphragm replacement (original JBL or aftermarket)
- Cleaning of the phase plug and throat
- Re-soldering of connection terminals
- Re-foaming or re-sealing of driver-to-horn interface
Many 2420 drivers remain in service 40+ years after manufacture.
Compatible Horn Lenses
The 2420's 2-inch throat pairs with JBL's professional horn lens systems:
- JBL 2307 / 2308 - 80° x 45° bi-radial horn system (used in 4355 studio monitors)
- JBL 2390 - 100° x 45° folded-plate lens (with 2327 adapter or native 2" entry)
- JBL 2392 - 80° x 45° slant-plate lens assembly for 2" drivers
- JBL 2395 - 140° x 45° wide-coverage lens (with 2327 adapter)
Related Drivers
- JBL 2421 - Evolution with improved phase plug
- JBL 2441 - Larger 4-inch diaphragm professional driver
- JBL 2405 - Slot tweeter/ultra-high frequency driver often used alongside the 2420
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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