JBL 2308

A slant plate acoustic lens built for precision dispersion, not show—light as a paperback at 0.5kg, yet pivotal in shaping the sound of JBL’s pro-grade horn systems

Overview

The JBL 2308 isn't an amplifier, speaker, or crossover—it’s a lens. Specifically, a 25.4 cm slant plate type acoustic lens designed to refine how sound exits a horn assembly. At just 254 mm wide and 63 mm deep, it’s a compact device, but its role is outsized: it controls dispersion in short-distance applications when paired with JBL’s 2307 or 2311 horns.

This is not a consumer-facing product. It emerged from JBL’s professional audio lineage, where precision and repeatability mattered more than aesthetics or ease of use. The 2308’s directional characteristics are rated at 80° horizontal by 45° vertical, measured with the 2307 and 2311 horns attached, suggesting a tightly controlled vertical dispersion pattern ideal for minimizing ceiling and floor reflections. While small and unassuming, its geometry plays a critical role in ensuring high-frequency energy is directed where it’s needed—toward the audience, not scattered.

Specifications

Manufacturer	JBL
Type	Lens
External dimensions	Width 254x Height 156x Depth 63 mm
Weight	0.5kg
Directional	80 ° x45 ° (measured with 2307, 2311 horns attached)
Description	25.4 cm slant plate type acoustic lens.
Throat exit	2
Frequency Response	500Hz~20kHz ±3db

Key Features

Slant Plate Geometry for Controlled Dispersion

The 2308’s core innovation lies in its slanted plate design, which refracts high-frequency output from the compression driver and horn throat to achieve a consistent 80° x 45° dispersion pattern. This geometry helps maintain uniform coverage across an audience plane, reducing hot spots and comb filtering. Unlike later waveguides that integrate into the horn body, the 2308 is an add-on component, allowing system designers to switch or remove it depending on venue acoustics. The 25.4 cm measurement refers to the effective aperture size, aligning with the throat dimensions of the 2307 and 2311 horns.

Velcro Tape Mounting System

Rather than relying on screws or clamps, the 2308 uses attached Velcro tape to secure the baffle plate to the horn assembly. This design choice reflects its intended use in touring and installed sound environments, where rapid setup and teardown were priorities.

Two-Throat Exit Design

The “throat exit 2” specification indicates the lens interfaces with a dual-throat horn configuration, likely allowing for symmetrical loading of the compression driver or bi-radial dispersion control. This feature is critical when used with the 2307 or 2311 horns, which may utilize dual-path acoustic channels to improve high-frequency coherence.

Historical Context

Priced at ¥10,000 around 1978 and rising to ¥14,000 by 1983, the 2308 was a specialized component rather than a standalone product. It was sold as a single unit, reflecting its role as a system upgrade or replacement part. Its integration into the JBL 2391 assembly—comprising the 2307 horn and 2308 lens—positions it within JBL’s professional loudspeaker ecosystem of the late 1970s and early 1980s. No official production years are documented, but its pricing history aligns with JBL’s broader horn development timeline during that period. It was not marketed to consumers but rather to sound contractors, studios, and touring companies who valued predictable dispersion characteristics.

Collectibility & Value

The 2308 has developed a quiet afterlife among vintage JBL enthusiasts and DIY audio builders. Used units reportedly sold for around $300 on eBay a few years ago, though current market availability is sparse. Due to scarcity, reproductions have emerged: KENRICK SOUND offers brand new replicas, and 3D-printed replacements appear on eBay, often labeled as “3D Replacement.” These clones suggest ongoing demand, particularly from restorers of vintage JBL systems. The original construction reportedly used glued blades, a potential point of failure over decades, while reproductions advertise one-piece builds for improved durability. Hifi Shark tracks used sales prices, indicating measurable collector interest despite the unit’s niche function.

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