JBL 4311 Control Monitor

1971 - 1975

The JBL 4311 Control Monitor sits between the 4310 and the 4312. Introduced in 1971, this three-way studio monitor kept the formula of its predecessor and improved the drivers and the crossover design. Many people consider it the sweet spot in JBL's compact monitor lineup.

Overview

Type	Three-way studio monitor
Enclosure	Sealed (acoustic suspension)
Dimensions	24.5" H × 14" W × 12" D (622 × 356 × 305 mm)
Weight	46 lbs (21 kg)
Impedance	8 ohms
Sensitivity	91 dB (1W/1m)
Power Handling	75 watts RMS
Frequency Response	45 Hz - 15 kHz (±3dB)
Crossover Frequencies	1,500 Hz and 6,000 Hz

Driver Configuration

Woofer: 10" JBL 123A-3 with improved suspension and magnet structure
Midrange: 5" JBL LE5-2 phenolic ring radiator
Tweeter: JBL LE25-4 1" dome tweeter

History & Design Evolution

JBL built the 4311 on the success of the 4310. Engineers there identified areas to refine:

Woofer Upgrade: The 123A-3 woofer featured a more robust suspension system that improved linearity and reduced distortion at higher excursion levels
Crossover Refinement: Subtle adjustments to the crossover network improved phase coherence between drivers
Cabinet Damping: Enhanced internal damping materials reduced cabinet resonances
Terminal Improvements: More robust binding posts for professional studio use

The 4311 is a transitional design. It keeps the Alnico magnet structure of the 4310 era, while taking in design lessons that would lead to the ferrite-magnet 4312. That gives it a sonic character that blends the warmth of early JBL designs with the improved technical performance of later models.

Sound Character

Many engineers describe the 4311 as the "classic JBL monitor sound" - a balanced presentation with several distinctive characteristics:

Forward Midrange - The LE5-2 midrange driver provides exceptional clarity and presence in the critical vocal range
Extended Bass - Despite its compact size, the 4311 delivers surprisingly deep and articulate bass response
Smooth Highs - The LE25 tweeter offers detailed but non-fatiguing high-frequency reproduction
Dynamic Punch - High sensitivity allows the 4311 to deliver explosive transients and uncompressed dynamics
Wide Dispersion - Excellent off-axis response makes the 4311 forgiving of less-than-ideal listening positions

Compared to the 4310, the 4311 offers slightly better bass control and lower distortion. Compared to the 4312, it has a touch more midrange warmth and a slightly more forgiving high end. That makes it well suited to long mixing sessions where fatigue can be an issue.

Studio Legacy

The 4311 found favor in many professional studios during its production run. Its balanced character made it a good fit for:

Critical Mixing: The revealing midrange helped engineers make precise EQ decisions
Tracking: Musicians appreciated the 4311's ability to reveal subtle performance nuances
Broadcast: Radio stations valued its consistent performance and reliability

While not as ubiquitous as the 4310 or 4312, the 4311 developed a loyal following among engineers who appreciated its refined balance between technical accuracy and musical engagement.

Collector's Notes

Today, the 4311 has its own place in the vintage audio market:

Relative Rarity: With a shorter production run than the 4310 or 4312, well-preserved 4311s are less common
Restoration Considerations: Like all vintage JBLs, the 4311 may need crossover recapping and L-pad cleaning/replacement
Driver Compatibility: Many 4311 components are interchangeable with 4310 and early 4312 models
Value Proposition: Often overlooked in favor of its more famous siblings, the 4311 can represent excellent value for vintage monitor enthusiasts

Common Issues to Check:

Foam surrounds on the 123A-3 woofer (later replaced with rubber in some units)
L-pad controls for midrange and tweeter levels
Crossover capacitors (electrolytics dry out over time)
Cabinet corners and veneer condition

Listening Tips: The 4311 responds well to quality amplification and proper placement. Allow at least 12 inches from walls for the best bass response, and consider isolation pads or stands to decouple it from surfaces.