JBL L100 Century (1970)

Name: JBL L100 Century
Brand: JBL

A foam-grilled floorstander from the 1970s, and a loud one.

Overview

A pair of JBL L100 Centurys is hard to mistake for anything else from its era. JBL introduced the model in 1970. It has a sculpted cabinet, drivers aligned on the centerline, and a pyramid-textured foam grille that came in bold colors. This became the best-selling loudspeaker of any brand in the 1970s, with over 125,000 pairs sold. It is built around the DNA of JBL's pro-grade 4310 studio monitor, dressed up for the consumer market. It's a 3-way, bass-reflex floorstanding speaker, and at 55 pounds each it is hefty. It was engineered to play loud without flinching, which is what the era demanded.

Specifications

Manufacturer	JBL (James B. Lansing Sound, Incorporated)
Model	L100 Century
Type	3-way bookshelf/floorstanding loudspeaker, bass reflex system
Woofer	12" (30cm) Cone Type (123A or 123A-1)
Midrange	5" (13cm) Cone Type (LE5-2 or LE5-3)
Tweeter	1-3/4" (4cm) Cone Type (LE25 or LE25-1)
Network	Dedicated 3-way network
Impedance	8 Ω
Allowable input	50W (continuous program)
Crossover frequency	1.5 kHz, 6 kHz
External dimensions	600mm H x 370mm W x 350mm D (23.5" x 14.5" x 13.75")
Weight	25kg (55 lbs) per speaker
Sensitivity	91 dB (1W/1m)
Cabinet volume	44 liters
Frequency Response	45Hz to 20kHz
Enclosure Type	Bass Reflex

Key Features

The Foam That Defined a Decade

The grille is JBL's Chad Cadrex II, an open-cell foam with truncated pyramids that give it a scalloped texture. It was a functional acoustic cover as well as a styling piece, but time hasn't been kind to it. The foam came in blue, orange, and brown/black, and it is notorious for disintegrating into dust. That leaves a mess and a bare frame. Many owners now fit replacement cloth grilles. Purists hunt down original foam in good condition.

Pro-Grade Drivers, Home-Focused Layout

Behind the foam is a 12-inch 123A woofer, a 5-inch LE5-2 midrange, and a 1-3/4-inch LE25 cone tweeter. All three sit vertically on the baffle's centerline, a layout that improved imaging and coherence. The bass and midrange drivers use Alnico V magnets, prized for their smooth magnetic field and vintage warmth. The tweeter uses a ferrite magnet. That's JBL being practical: the best parts where it mattered most, cheaper ones where it didn't.

Front-Panel Tone Controls (Yes, Really)

The front panel carries a pair of attenuators. These are Alps L-Pad potentiometers, and they let you turn down the midrange and high-frequency output. That was a bold move for a high-end speaker, since it admitted that not every room or listener wants the full JBL "forward" sound. The L-Pads are also a known failure point. Over decades they develop crackle and dropouts, and restoration means cleaning or replacing them.

The Crossover: Simple, But a Weak Link

The internal 3-way network uses basic high-pass filters, an 8 µF capacitor to the midrange and 3 µF to the tweeter, plus the L-Pads for attenuation. It works, but owners report that the original components, especially the capacitors, degrade over time. The result is dull highs or an imbalance. Recapping the crossover is a common upgrade, though purists debate whether modern parts preserve the original character.

Historical Context

The L100 Century came out of studio success. The JBL 4310 control monitor had become a staple in recording studios, and its accuracy and durability made it a favorite. JBL took that proven transducer lineup, put it in a cabinet designed for the home, and added some visual drama. The L100 is the consumer version of the 4310, with a bolder look and features like the front-panel attenuators. By the end of the 1970s, JBL monitors dominated US studios.

Collectibility & Value

Today, a pair of JBL L100 Centurys in good condition trades for $1,200 to $1,500. "Good condition" is doing a lot of work there. The foam grilles almost always need replacement or repair, and the L-Pad controls frequently need servicing. Aging crossover capacitors can dull the sound, so many buyers look for fully restored pairs. Refoaming, recapping, and cleaning the attenuators are the standard restoration steps. If you're hunting originals, check for intact foam, clean controls, and evidence of electrical refurbishment.