JBL 4311B Control Monitor

Name: JBL 4311B Control Monitor
Brand: JBL

1976 - 1980

The JBL 4311B Control Monitor is the last evolution of the 4311 platform. Introduced in 1976, this "B" version refined the crossover network and driver integration of the original 4311, which was already a studio favorite. Many engineers consider it the best expression of JBL's compact three-way approach.

Overview

Type	Three-way studio monitor
Enclosure	Bass reflex (ported)
Dimensions	24.5" H × 14" W × 12" D (622 × 356 × 305 mm)
Weight	48 lbs (22 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: 12" JBL 2213H with ferrite magnet and white paper cone
Midrange: 5" JBL LE5-2 phenolic ring radiator
Tweeter: JBL LE25 1" dome tweeter

History & Design Evolution

The 4311B was more than a simple model revision. The "B" designation signaled upgrades that addressed specific observations from engineers who had been using 4311 monitors daily:

Crossover Refinement: The most significant change came in the crossover network, with revised component values that improved phase coherence between drivers
Driver Matching: Tighter manufacturing tolerances ensured more consistent driver-to-driver performance
Enclosure Tuning: Subtle modifications to the bass reflex port improved transient response and reduced port noise
Component Upgrades: Higher-grade capacitors and resistors in the crossover network enhanced long-term reliability

The 4311B arrived as the industry moved from 16-track to 24-track recording. Denser mixes demanded monitors with more resolution. The refined crossover and improved driver integration gave engineers the precision they needed.

Against its contemporaries, the 4311B kept the musical warmth that made JBL monitors popular while delivering the analytical precision needed for critical mixing decisions. Few manufacturers managed that balance.

Sound Character

The 4311B refines the classic JBL sound with subtle improvements:

Improved Driver Integration - The revised crossover creates a more seamless transition between drivers, with less audible discontinuity at crossover frequencies
Tighter Bass - Enhanced port tuning and refined woofer control deliver more articulate low-frequency performance
Smoother Midrange - The LE5-2's already excellent performance is further optimized through improved network design
Extended Dynamics - Better power distribution across drivers allows higher SPLs with reduced distortion
Refined Imaging - Improved phase coherence creates a more stable, three-dimensional soundstage

Compared to the original 4311, the "B" version sounds slightly more refined, with better resolution of fine detail. The bass is still powerful and extended, but it has better control and definition. The midrange keeps its characteristic presence and shows subtle details more clearly.

Many engineers describe the 4311B as "the 4311 perfected" - it keeps everything that made the original popular and fixes minor shortcomings that showed up after years of professional use.

Studio Legacy

The 4311B continued and expanded on the original 4311's studio success:

Professional Adoption: Became the standard monitor in countless recording and broadcast facilities
Mixing Excellence: Engineers appreciated the improved detail retrieval for critical EQ and balance decisions
Broadcast Applications: The refined sound character proved ideal for radio and television broadcast monitoring
Educational Institutions: Audio programs valued the 4311B's combination of accuracy and durability

Technical Improvements

The 4311B made several technical advances over its predecessor:

Enhanced Crossover Topology: Revised network design with improved phase characteristics
Better Quality Components: Higher-grade capacitors with tighter tolerances
Improved Terminal Block: More robust binding posts for professional use
Refined Cabinet Bracing: Internal structural improvements reduced resonances

Collector's Notes

The 4311B is good value for vintage monitor buyers:

Availability: Produced in significant quantities, making well-preserved examples findable
Build Quality: Professional-grade construction ensures longevity with proper care
Restoration Considerations: Crossover recap recommended; L-pads may need cleaning
Investment Value: Strong demand from both collectors and working engineers

Common Issues to Check:

Crossover capacitors (electrolytics likely need replacement after decades)
L-pad controls for midrange and tweeter levels
Woofer surround condition (foam may need refoaming)
White cone appearance (some yellowing is normal with age)
Cabinet integrity (check for water damage or delamination)

Variant Identification: The 4311B can be told apart from earlier 4311 models by its serial number and internal crossover component values. Later production runs may have slight component variations based on parts availability.

Listening Tips: The 4311B responds well to quality amplification with good current delivery. The front-panel L-pad controls allow room tuning - start flat and adjust to your acoustic environment. Position at least 12 inches from walls for the best bass response.