JBL 2391 / 2392 Horn & Lens Assemblies
The JBL 2391 and 2392 are slant-plate horn assemblies for high-frequency control in studio and sound reinforcement systems. The 2391 pairs the 2307 horn with the 2308 lens for 1" drivers. The 2392 mates the shorter 2311 horn with the same 2308 lens, and it is made for 2" drivers. Both give an 80° horizontal by 45° vertical coverage pattern. They turn up in vintage JBL multi-way systems where clarity and directionality matter.
Specifications
| Type | Slant-Plate Acoustic Lens with Exponential Horn |
|---|---|
| 2391 Components | 2307 Horn + 2308 Lens (for 1" drivers) |
| 2392 Components | 2311 Horn + 2308 Lens (for 2" drivers) |
| Coverage Pattern | 80° horizontal x 45° vertical (above 1200 Hz) |
| Frequency Range | Above 800-1200 Hz (800 Hz for short throw, 1200 Hz recommended) |
| Sensitivity | 108 dB (1W/1m, 4V into 16Ω, warbled crossover to 2.5 kHz) |
| Throat Diameter (2391) | 25 mm (1 inch) - accepts 1" drivers only |
| Throat Diameter (2392) | 50 mm (2 inch) - accepts 2" drivers |
| Nominal Q | 2.5 (2 kHz octave band) |
| Maximum Throw | 9 m (30 ft) |
| Horn Dimensions (2391) | 156 x 197 mm (6⅛ x 7¾ in) |
| Horn Dimensions (2392) | 156 x 117 mm (6⅛ x 4⅝ in) |
| Lens Dimensions | 156 x 254 x 56 mm (6⅛ x 10 x 2¼ in) |
| Weight | 1.8 kg (4 lb) |
Design Overview
JBL’s slant-plate lens technology was a game-changer for consistent high-frequency dispersion—and the 2391 and 2392 put it on full display. At their core is the 2308 slant-plate lens, a precision-machined waveguide that angles sound into a stable 80° x 45° pattern. Paired with the right horn, it tames the wild highs and delivers uniform coverage across the listening plane.
The 2391 uses the deeper 2307 horn, tuned for 1" compression drivers. That gives it a slightly extended reach and tighter focus. The 2392 has the shorter 2311 horn and is built for 2" drivers. It puts out plenty of level with the same controlled dispersion. Both hold their pattern above 1200 Hz.
Installation Requirements
These are not plug-and-play add-ons. They need proper mounting to work as designed. Without a cabinet, each assembly needs a minimum 300 mm x 300 mm (12" x 12") baffle to prevent rear wave interference. The sides of the lens plate must stay unobstructed, because any blockage disrupts the wavefront and smears the high end. The seal between driver and horn throat must also be airtight. Leaks there kill efficiency and muddy the response.
Crossover Recommendations
While 1200 Hz is the sweet spot for most setups, the 2391 and 2392 offer flexibility. Running them at 1200 Hz ensures optimal pattern control and driver protection. But in short-throw applications—especially within integrated systems—dropping to 800 Hz is viable, provided the driver can handle the lower excursion. It’s a balance: push the crossover down, and you gain output at the cost of dispersion precision.
Compatible Drivers
2391 (1" throat):
- JBL LE85 - Classic 1" compression driver
- JBL 2425 - Titanium diaphragm 1" driver
- Other professional 1" throat compression drivers
2392 (2" throat):
- JBL 2420 - 2" Alnico compression driver
- JBL 2421 - Evolution with improved phase plug
- JBL 2441 - 4" diaphragm professional driver
- Other 2" throat compression drivers
Applications
These assemblies were built for purpose. In professional studio monitors, they deliver crisp, focused highs without coloration. In two- or three-way systems, they integrate seamlessly, offering predictable coverage and strong output. Whether reinforcing sound in a theater, a broadcast booth, or a vintage hi-fi stack, the 2391 and 2392 excel where throw and directionality matter—up to 9 meters with confidence.
Comparison to 2307/2308
The 2307/2308 combination is essentially the disassembled version of the 2391. The 2391 packages the 2307 horn and 2308 lens as a ready-to-mount unit. The 2307/2308 documentation focuses on DIY integration, especially for builds like the 4355 studio monitor. Performance is the same. Only the path to installation differs.
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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