JBL 4315B (1980)

Name: JBL 4315B
Brand: JBL

Fire up a pair and every layer in a mix comes through like it's the first time. That is why engineers trusted the 4315B.

Overview

The JBL 4315B is a studio monitor that sat on console bridges in Tokyo, Paris, and New York, telling engineers exactly what their mixes were doing, warts and all. It came out in 1980 as a refined version of the 4315A. It is a 4-way, bass-reflex, bookshelf-type system built for accuracy and durability. It is not flashy and not forgiving, which is what you want when you're making final calls on a master. The 4315B and its walnut-finished sibling, the 4315BWX, were priced around ¥400,000 and ¥410,000 respectively in 1981. That is steep, and it reflected their professional use. These weren't living-room showpieces. They had gray vinyl veneer, a black grille, and a no-nonsense look.

Owners report a sound that's crystal clear in the vocal and high-frequency ranges. One user says they hear instruments in familiar tracks that went unnoticed on other systems. Another called their setup with the 4315Bs "nothing short of enchanting." Some find the upper midrange and treble a bit forward, and they often dial it back with the front-panel L-pads by about -2dB to keep the sound rounded and balanced. The speakers were designed to be dialed in, not just plugged in.

Specifications

Manufacturer	JBL (James B. Lansing Sound, Incorporated)
Model	4315B / 4315BWX
Type	4-way, 4-speaker, bass reflex system, bookshelf type speaker system
Drivers	Low range: 30 cm cone type woofer 2203H; Middle range: 20 cm cone type mid-woofer 2108H; Middle and high range: 13 cm cone type 2105H; High range: Horn type tweeter 2405
Frequency Response	35 Hz to 20 kHz ± 3 dB
Crossover Frequencies	400 Hz, 2 kHz, 8 kHz
Nominal Impedance	8 Ω
Sensitivity	89 dB/W/m
Power Handling	60W (network)
Enclosure Volume	Woofer: 91L; Mid-Woofer: 2.8L
Dimensions (W x H x D)	521 x 854 x 327 mm
Weight	47.6 kg

Key Features

Four-Way Driver Array with Targeted Upgrades

The 4315B is a 4-way system, meaning it splits the audio signal across four drivers: woofer, mid-woofer, mid/high, and tweeter. Each handles a slice of the spectrum, which allows greater control and reduced distortion. It was developed as a unit modification of the 4315A, with three of the four drivers updated. The low end now uses the 2203H 30 cm cone woofer, the midrange gets the 2108H 20 cm mid-woofer, and the mid/high duties fall to the 2105H 13 cm cone driver. Only the high-frequency horn, the 2405, carries over unchanged.

Tractrix Horn with Acoustic Lens

The 2405 horn-type tweeter is fronted by an acoustic lens, also called a diffraction lens. It helps smooth high-frequency dispersion and reduce edge diffraction. That gives a more consistent off-axis response, which helps in control rooms where reflections can muddy the sound. The horn's directional pattern is rated at 80° x 60° at 16 kHz, giving engineers a focused sweet spot without being overly narrow.

Modular Cabinet with Professional Mounting

The cabinet is a bass-reflex design. The port extends low-frequency response and efficiency. It is built from wood with a vinyl veneer, which is practical, durable, and easy to maintain in a studio. The 4315B comes in a gray finish with a black grille, while the BWX variant has a walnut finish and blue grille. On the back, metal support fittings allow the speaker to be suspended, so it could be adapted to different studio layouts, from console mounting to wall rigging.

Historical Context

The 4315B arrived in 1980 as part of JBL's 4300 Series, which was originally launched in 1973. It belongs to the broader '43xx' series of studio monitors, known for no-compromise engineering and broadcast-grade reliability. The fact sheet doesn't detail the design goals or competitive landscape. The specs and build suggest it was aimed at professional users who needed a compact, full-range monitor that could handle high SPLs with precision.

Collectibility & Value

Asking prices today run from $1,200 to $1,800, though some listings go much higher, up to $4,750 or even $10,000 in exceptional cases. Condition is everything. Original, unmodified units with intact drivers and clean grilles hold the most value. The gray-finish 4315B is common, but the walnut-finished BWX often draws a premium.

Common issues include degraded foam surrounds on the woofers and mid-woofers, which are prone to rot after decades of use. Replacement foam kits are widely available, making this a manageable restoration. The L-pads on the front panel, used to adjust treble and upper midrange levels, can become scratchy or intermittent over time and may need cleaning or replacement. Another known failure point is the 10-watt power resistors in the crossover—owners report broken leads due to vibration-induced metal fatigue, a flaw that can be fixed but requires careful soldering. Despite these quirks, the 4315B’s reputation for great sound and build quality keeps demand steady among collectors and studio nostalgics.