JBL 4345 (1981)

When a speaker weighs over 100 kilos and still manages to disappear in a room full of sound, you know you're in the presence of something monumental.

Overview

The JBL 4345 isn’t just a speaker—it’s a statement in industrial acoustics. Released in 1981 as part of the legendary 4300 Series, this floor-standing, four-way, four-speaker bass reflex system was engineered for one purpose: to deliver unflinching accuracy at concert-hall sound pressure levels. Built for professional studio monitoring, it commands space not just physically—thanks to its 104kg frame and nearly 1.1-meter height—but sonically, with a presence that refuses to be ignored.

Manufactured by JBL (James B. Lansing Sound, Incorporated), the 4345 was never intended for the average living room. This is a monitor for engineers who demand transparency, durability, and sheer dynamic authority across all genres. With its blue-painted baffle, oil-finished walnut veneer, and imposing proportions, it looks as serious as it sounds. Priced at ¥850,000 per unit at launch, it was a premium tool from the start—rare, purpose-built, and uncompromising.

Key Features

18-Inch 2245H Woofer with SFG Magnetic Circuit: Deep, Controlled Bass

At the heart of the 4345’s authority is its 18-inch 2245H woofer—a massive cone driver built with JBL’s proprietary SFG (Symmetric Field Geometry) magnetic circuit and damped with Lansa-Plus on the back of the cone. That combination delivers deep, controlled bass with high linear peak displacement (20 mm), essential for handling high-SPL transients without distortion. The voice coil itself is a beast: 100 mm in diameter and 25 mm long, designed to dissipate heat and maintain performance under sustained loads. This isn’t a driver that flinches under pressure; it’s built to dominate low-frequency reproduction in large control rooms where accuracy under extreme conditions is non-negotiable.

10-Inch 2122H Low-Mid Driver in Sealed Cavity: Precision and Speed

Handling the low-mid range is the 2122H 10-inch driver, also featuring SFG technology and a 75 mm copper ribbon voice coil. Its cone uses a new paper formulation for improved rigidity, reducing breakup modes and enhancing transient response. Unlike the woofer, this driver operates in a sealed back cavity—a design choice that improves damping and minimizes phase distortion. Paired with the larger woofer in a vertical mirror image layout, the system achieves precise stereo imaging and reduced cabinet coloration, critical for accurate panning and spatial cues in mixing environments.

Bi-Radial Horn with 2420 Driver, 2307 Horn, and 2308 Lens: Controlled Dispersion

The high-frequency section combines the 2420 compression driver with the 2307 horn and 2308 acoustic lens, mounted on the baffle using Velcro tape for easy servicing—a rare touch of practicality in such a serious design. this Bi-Radial horn setup delivers controlled dispersion: horizontal 80° x vertical 45°—a critical feature for consistent off-axis response in studio environments. This ensures that engineers hear the same tonal balance whether seated directly on-axis or moving slightly to the side, reducing ear fatigue during long sessions.

2405H Slot Radiator with Ultra-Thin Ring Diaphragm: Extended Highs

The ultra-highs are handled by the 2405H slot radiator, a horn tweeter with an ultra-thin ring diaphragm known for its extended response and 140° horizontal dispersion at 10 kHz. It’s this driver that gives the 4345 its crystalline top end—though owners note it can become piercing if the source chain has any high-frequency glare. That precision is a double-edged sword: it reveals every flaw in recordings, making it a trusted tool for critical listening, but also demanding careful system matching to avoid listener fatigue.

High-Isolation Crossover with Charge-Coupled Configuration: Driver Decoupling

The crossover network is a key part of the design: JBL’s new high-isolation layout uses a charge-coupled configuration with a small-capacitance capacitor added in parallel to a high-capacitance one, minimizing interaction between drivers. This reduces intermodulation distortion and ensures clean signal separation across the frequency bands. For maximum control, the internal crossover can be split for bi-amping—allowing separate amplification of low and high-frequency sections, with dedicated power ratings of 200W for the low end and 100W for the highs. In network mode, the system handles 120W, making it flexible for both passive and active configurations.

Asymmetrically Braced 21mm Particle Board Enclosure: Resonance Control

The enclosure itself is built from 21 mm thick rigid particle board with asymmetric internal bracing, further reducing resonance. The cabinet is divided into two volumes: 253L for the woofer and 14L for the mid-woofer, optimized for their respective drivers. This bass reflex design allows for deeper extension and higher efficiency than sealed alternatives, crucial for maintaining headroom in high-SPL environments. The result is a speaker that remains neutral even at reference levels, without the boxy coloration that plagues lesser designs.

Historical Context

Though the series began earlier, the 4345 arrived in 1981 as a late but definitive evolution—bigger, more powerful, and more refined than its predecessors. It was designed by Greg Timbers and positioned as the larger sibling to the 4343, sharing the same driver layout but scaled up significantly in cabinet volume to accommodate the 18-inch woofer. That extra space translates directly into deeper bass and greater dynamic headroom, making the 4345 a true full-range monitor capable of operating without subwoofers in large control rooms.

Despite its capabilities, the 4345 remained a niche product—built for professional use, rare in production, and never intended for mass adoption. Modern-Recording (March 1982, p.22) noted the 4345 was "designed for large scale studio installation where extremely high sound pressure levels are required," confirming its role as a workhorse for broadcast and mastering facilities. Today, it’s recognized as a legacy product within JBL Professional’s lineup, a symbol of an era when brute-force engineering met acoustic precision.

Collectibility & Value

Today, the JBL 4345 is a coveted piece among vintage monitor collectors. Its rarity and performance have created a market where demand consistently outpaces supply.

Restoration is often necessary.

Despite the upkeep, many consider these speakers a sound financial bet. As one owner put it: “Good investments, used JBL, as they keep their value over decades. Like money in the bank, when finished with JBL speakers, just sell 'em and get all your money back.”