JBL 4350 (1973–1975)

At 125 kg, it anchors a room.

Overview

The JBL 4350 is a floor-standing, four-way studio monitor built with no compromises. Introduced around April 1973, it was a top-tier reference speaker from an era when accuracy and brute output defined professional monitoring. It weighs 125 kg, so check the floorboards. The mass comes from a 269-liter enclosure built from 20 mm thick material, housing five drivers in a bass reflex configuration. The design target is 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, and it was one of JBL's most ambitious studio projects of the decade.

It was the premier studio reference during its heyday in the 1970s and early 1980s. Studios that could afford it installed them. The British rock band The Who equipped the control room of their Rampart Studios in Twickenham, England, with twelve JBL 4350s. Sensitivity is 95.5 dB (1W, 1m, New JIS), and it can reach 126 dB at 10 feet under program conditions. That is enough to shake the walls of a control room or a 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

Key Features

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

The JBL 4350 uses two 38 cm (15") 2230A cone drivers for low frequencies. Each has a treated paper cone and an edgewise wound copper voice coil. That gives high excursion capability and thermal stability, which they need to handle 200W of continuous program power below 250 Hz. Two woofers mean more cone area and output, which supports the 30 Hz low-end extension without port compression. The bass reflex design adds efficiency in the lower register, but it needs careful room placement to avoid boominess.

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

The 30 cm (12") 2202A mid-bass driver is precision machined and mounted in a 34-liter sealed back chamber. That isolates it from the main woofers, which reduces intermodulation distortion and keeps mid-bass articulation clean. It handles the 250 Hz to 1.1 kHz band, between the lows and the horn-loaded midrange. Keeping the drivers from interacting was a JBL priority, and it was common in 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 has a thin aluminum-alloy diaphragm and an edgewise wound aluminum voice coil, which gives fast transient response and high power handling. The horn gives high efficiency and controlled dispersion, which matters for monitoring at high SPLs. This section runs from 1.1 kHz to 9 kHz and feeds 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. The design minimizes breakup modes and gives smooth, extended high-frequency response up to 20 kHz. Compared with a conventional dome tweeter, the ring radiator offers broader dispersion and lower distortion at high output levels. It is a signature JBL high-frequency design, refined here for studio use.

Hybrid Active/Passive Crossover System

The 4350 uses a hybrid crossover. Frequencies below 250 Hz are handled by an external active crossover, typically the JBL 5231 or 5232 electronic dividing network, which allows 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. Splitting the job this way reduces stress on the passive components and improves 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 stayed in production until 1975. It was marketed as a high-performance studio monitor and found homes in elite studios where accuracy and output were non-negotiable. The Who used it at Rampart Studios. No official product family hierarchy is documented, but its complexity and cost make it 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.

eBay Listings

jBL Foilcal L100, L300, L200, L65 Jubal, L112, 4350, New Rep

$175

JBL Holidays, 4343, L100 L300 4350 Stain Glass SUN Catcher T

$28.95

Two New JBL 4350 Grilles New JBL Badges Fully Assembled Read

$799

JBL 4350 Pair Used With Electronic Crossover Model 5234

$28,999

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