JBL 4345 (1981)

Name: JBL 4345
Brand: JBL

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.

Specifications

Manufacturer	JBL
Model	4345
Type	Professional series large speaker system, 4-Way, 4-Speaker, Bass Reflex System, Floor Type
Frequency Response	32 Hz to 20 kHz ± 3 dB
Directional	Horizontal 60° x Vertical 30° (-3dB, 16 kHz)
Sensitivity	95dB/W/m
Nominal Impedance	8 Ω
Power Handling	120W (network), 200W (Multi-Amp Lo), 100W (Multi-Amplifier Hi)
Crossover Frequencies	Network: 320 Hz, 1.3 kHz, 10 kHz; Bi-amplifier: 290 Hz, 18dB/oct.
Enclosure Volume	253L (Woofer), 14L (mid-woofer)
Dimensions (H×W×D)	1096mm × 765mm × 470mm
Weight	104kg
Drivers	Low Frequency: 2245H 18-inch; Low-Mid Frequency: 2122H 10-inch; High Frequency: 2420 on 2307 horn + 2308 lens; Ultra High Frequency: 2405H slot radiator
Finish	Blue painted baffle, oil-finished walnut veneer
Production Years	1981

Key Features

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.

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 new paper formulation for improved rigidity, and it operates in a sealed back cavity—a design choice that enhances transient response and reduces unwanted resonance. Paired with the larger woofer in a vertical mirror image layout, the system achieves precise stereo imaging and reduced cabinet coloration.

The high-frequency section combines the 2420 driver with the 2307 horn and 2308 acoustic lens, mounted on the baffle using Velcro tape for easy servicing. When installed on a sufficiently large baffle (30 cm or more in each dimension), this Bi-Radial horn setup delivers controlled dispersion: horizontal 80° x vertical 45°—a critical feature for consistent off-axis response in studio environments. 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.

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. The enclosure itself is built from 21 mm thick rigid particle board with asymmetric internal bracing, further reducing resonance. And for those who want 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.

Historical Context

The 4345 was part of the 4300 Series, which JBL launched in 1973 and which included the industry’s first 4-way speaker. 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. 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. SkyFi Audio listed a pair as sold out in 2022 with no price disclosed, while another listing on US Audio Mart asked $12,000 as of December 30, 2022. A dealer in Moscow claimed to sell a perfect pair for $15,000 in 2010, and forum reports suggest prices have ranged from $1,000 to $5,000 depending on condition—though high-end restored pairs clearly command much more.

Restoration is often necessary. Midrange drivers may require surround replacement—a service performed by specialists like Millersound—and woofers frequently need refoaming. Audio Classics redid a pair of main woofers in 2019 using original JBL parts, and one owner reported refoaming his pair just two years prior. Reconing kits are available, such as the FSK-18JBL-1 for the 18-inch woofer, but sourcing parts can take months. Original grills are often present but typically need new cloth.

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.”