JBL 4350 (1973–1975)

At 125 kg, it doesn’t just anchor a room—it commands it.

Overview

The JBL 4350 is a floor-standing, four-way studio monitor built for no compromise. Introduced around April 1973, it was engineered as a top-tier reference speaker during an era when accuracy and brute output capability defined professional monitoring. Weighing in at 125 kg, this is not a speaker for the faint of floorboards. Its sheer mass comes from a 269-liter enclosure constructed from 20 mm thick material, housing five drivers in a bass reflex configuration designed to deliver flat response from 30 Hz to 20 kHz within ±3 dB. Owners report it was developed under the direction of Walter Dick and refined by Pat Everidge, marking it as one of JBL’s most ambitious studio projects of the decade.

It wasn’t just another monitor—it was the premier studio reference during its heyday in the 1970s and early 1980s. Studios that could afford it installed them with reverence. The British rock band The Who famously equipped the control room of their Rampart Studios in Twickenham, England, with twelve JBL 4350s, a testament to its dominance in high-end studio environments. With a sensitivity of 95.5 dB (1W, 1m, New JIS), it converts power to sound with ruthless efficiency, capable of reaching 126 dB at 10 feet under program conditions—enough to shake the walls of any control room or small live space.

Despite its size, the 4350 was engineered with surgical precision. Its dispersion is tightly controlled: 60 degrees horizontally and 30 degrees vertically within -3 dB up to 12 kHz, ensuring focused imaging and minimizing room interaction. This isn’t a speaker meant to flatter; it’s built to reveal. Third harmonic distortion remains under 1% at 108 dB SPL between 33 Hz and 1.2 kHz, and dips to ≤0.6% from 1.2 kHz to 5 kHz at 101 dB SPL—numbers that still impress by modern standards.

Specifications

Manufacturer	JBL
Model	4350
Production years	1973 to 1975
System Type	4-Way, 5-Speaker, Bass Reflex, Floor Type
Drivers	Low frequency: 38 cm (15") cone type (2230A) x2; Medium Low frequency: 30 cm (12") Cone Type (2202A); Mid/High frequency: Horn Type (2440 driver + 2311 horn + 2308 lens); High frequency: Ring Radiator Type (2405)
Frequency response	30 Hz to 20 kHz ± 3 dB
Dispersion (within -3dB up to 12 kHz)	Horizontal: 60 degrees; Vertical: 30 degrees
Power handling (continuous program)	250 Hz or less: 200W (4 Ω); 250 Hz or more: 100W (8 Ω)
Impedance	250 Hz or less: 4 Ω; 250 Hz or more: 8 Ω
Sensitivity/Sound Pressure Level	95.5 dB (1W, 1m, New JIS); Maximum SPL (10 ft): 110 dB (1/2 power pink noise), 126 dB (1/2 power program)
Third harmonic distortion	<1% (108 dB SPL, 10 ft, 33 Hz - 1.2 kHz); ≤0.6% (101 dB SPL, 10 ft, 1.2 kHz - 5 kHz)
Crossover frequencies	250 Hz (12dB/oct); 1.1 kHz, 9 kHz
Enclosure volume	269 L (including 34L isolated chamber for 2202A)
External dimensions	1,210 mm (W) x 890 mm (H) x 510 mm (D)
Weight	125 kg
Original price	993,800 yen
Available finishes	Gray or walnut

Key Features

38 cm (15") Dual Woofers with Treated Paper Cones

The JBL 4350 uses two 38 cm (15") 2230A cone drivers for low-frequency reproduction, each featuring treated paper cones and edgewise wound copper voice coils. This construction delivers high excursion capability and thermal stability, essential for handling 200W of continuous program power below 250 Hz. The dual-woofer setup increases cone area and output, enabling the 30 Hz low-end extension without port compression. The bass reflex design further enhances efficiency in the lower register, though it demands careful room placement to avoid boominess.

Isolated 30 cm (12") Mid-Bass Driver (2202A)

A standout engineering choice is the inclusion of a dedicated 30 cm (12") 2202A mid-bass driver, precision machined and mounted in a 34-liter sealed back chamber. This isolation prevents acoustic coupling with the main woofers, reducing intermodulation distortion and ensuring clean mid-bass articulation. The driver handles the 250 Hz to 1.1 kHz band, bridging the gap between thunderous lows and the horn-loaded midrange. This segmented approach reflects JBL’s commitment to minimizing driver interaction—a hallmark of high-end studio monitors of the era.

Horn-Loaded Mid/High Driver (2440 + 2311 + 2308)

The mid/high section combines the 2440 driver, 2311 horn, and 2308 lens in a constant-directivity horn assembly. The 2440 features a thin aluminum-alloy diaphragm and an edgewise wound aluminum voice coil, contributing to fast transient response and high power handling. The horn ensures high efficiency and controlled dispersion, critical for accurate monitoring at high SPLs. This system operates from 1.1 kHz to 9 kHz, feeding into the ring radiator for the top octave.

2405 Ring Radiator for Extended High Frequencies

Above 9 kHz, the 2405 ring radiator takes over, using a pressure-formed aluminum ring diaphragm. This design minimizes breakup modes and delivers smooth, extended high-frequency response up to 20 kHz. Unlike conventional dome tweeters, the ring radiator offers broader dispersion and lower distortion at high output levels. It’s a signature JBL high-frequency solution, refined here for studio-grade neutrality.

Hybrid Active/Passive Crossover System

The 4350 relies on a hybrid crossover strategy. Frequencies below 250 Hz are managed by an external active crossover—typically the JBL 5231 or 5232 electronic dividing network—allowing precise level and phase control for the woofers and mid-bass driver. Above 250 Hz, a passive L-C network handles the 1.1 kHz and 9 kHz crossovers. This division of labor reduces passive component stress and improves overall system coherence. Front-panel continuously variable level controls let engineers tailor the output of each section to room acoustics or program material.

Historical Context

The JBL 4350 was introduced around April 1973 and remained in production until 1975. Though short-lived, its impact was immediate in professional circles. Marketed as a high-performance studio monitor, it found homes in elite studios where accuracy and output were non-negotiable. Its adoption by The Who for Rampart Studios underscores its reputation for reliability and sonic authority. While no official product family hierarchy is documented, its complexity and cost position it as one of JBL’s flagship monitors of the early 1970s.

Collectibility & Value

Current market data is sparse, but asking prices reflect its legendary status. A pair was listed for $17,000 AUD in 2020, while another Kenrick Sound-modified version sought $18,500 in 2015. At that price point, it competes with other high-end vintage and modern used speakers. Age-related failures are expected—particularly deteriorated foam surrounds, a common issue in vintage JBL drivers. Re-foam kits for the midrange driver are available, and full rebuilds are not uncommon among dedicated owners. Given its weight, complexity, and need for external electronics, ownership is a commitment. But for those who value raw engineering and unfiltered studio transparency, the 4350 remains a grail.