JBL L-112 (1980–1985)

Name: jbl l-112
Brand: jbl

A 3-way bookshelf box with a 12-inch white-cone woofer, mirror-imaged pairs, and a dome tweeter JBL developed with laser holography - the consumer speaker that borrowed the lab's tools.

Overview

The L-112 is a 3-way, 3-speaker bass-reflex bookshelf system that JBL built from 1980 through 1985. It has a 30 cm cone woofer (the 128H), a 13 cm cone midrange (the LE5-12), and a 2.5 cm dome tweeter (the 044). The crossover splits them at 1.1 kHz and 3.7 kHz. JBL's own literature from the period called it "our most advanced bookshelf speaker system," and the advertising pushed the flatness of its response curve as the headline claim.

The numbers are modest on paper. Rated sensitivity is 89 dB SPL at 1 W, 1 m, and nominal impedance is 8 ohms. Allowable input is quoted as 80 W continuous program or 100 W under the IEC standard. The enclosure measures 362 mm wide by 622 mm tall by 333 mm deep. That makes it a "bookshelf" speaker only in the loosest sense, since it needs a real shelf or a stand rather than a slot between paperbacks. The front baffle carries continuously variable level controls for the midrange and high ranges, tucked behind the removable grille, so the balance can be trimmed to the room.

The driver engineering is what separates the L-112 from a generic three-way. The 128H woofer uses JBL's Symmetrical Field Geometry magnetic structure with a flux-stabilizing ring, and the cone carries a thick white coating formulated for the right mass and stiffness. The LE5-12 midrange sits in a fully enclosed subchamber so the woofer's backwave can't modulate it. The 044 dome is a phenolic diaphragm coated with aluminum by vapor deposition. JBL's manual describes using laser interferometry and holograms to study diaphragm motion during development.

Key Features

The 128H Woofer and Symmetrical Field Geometry

The 12-inch woofer's magnetic assembly is the part to understand. JBL's SFG design makes the field at the voice coil gap symmetrical and adds an aluminum Flux Stabilizing Ring. The manual says this dramatically reduces the second-harmonic distortion conventional drivers produce. A large voice coil and a powerful magnet give the driver high power handling and quick transient response. The idea is that the bass stays clean when the music gets loud. Owners have described a "bump" in the low end that flatters the speaker's apparent extension, though those same listeners note it doesn't reach as deep as JBL's larger systems.

The LE5-12 Midrange in Its Own Subchamber

The 13 cm midrange sits in a sealed back cavity. That keeps the woofer's rear output from interfering with the midrange cone, so vocals and instruments stay put instead of smearing. The driver pairs a stiff cone with a 22 mm voice coil for fast attack, which matters most on piano and cymbals. JBL's manual argues that music carries more energy in the midrange than in bass or treble, so the driver was given reserve dynamic range to handle peaks without strain.

The 044 Dome Tweeter

The 2.5 cm dome is formed from phenolic material and coated with aluminum through vapor deposition. A copper voice coil drives it around its full circumference. JBL developed it specifically for the L-112, using laser-optics work to evaluate diaphragm behavior. High Fidelity (January 1981, p.32) noted that the tweeter was described as an outgrowth of the company's optical interferometry techniques. The same magazine's coverage (p.47) characterized the phenolic vapor-deposition aluminum dome as a new class of tweeter performance for the model. The top end is meant to handle the loudest peaks without hardening while still resolving low-level detail.

Mirror-Imaged Pairs and Level Controls

The L-112 was designed in mirror-imaged pairs, so the left and right baffles are reflections of each other. JBL's reasoning is straightforward. Without mirror imaging, the different drivers' positions make different frequencies seem to come from different places, and the stereo image drifts. With it, the center image stays locked. The continuously variable mid and high level controls let owners compensate for a bright room or a dull one. The crossover is built on a heavy-duty printed circuit board, with each driver controlled across its full operating range rather than only at the transition frequencies.

Historical Context

The L-112 arrived in 1980, part of JBL's consumer speaker expansion through the late 1970s and early 1980s. It sat alongside the L65 Jubal, L150, and L300 Summit in the lineup. Production ran through 1985 according to the reference record, though at least one source places the introduction around 1981 after several iterations of the original L100 Century. That one-year discrepancy has never been fully settled.

Collectibility & Value

Restored pairs of the L-112 command real money, and parts still turn up. A professionally restored pair with a one-year warranty has been listed at $6,499, down from an $8,699 ask. Individual 044 tweeters trade in the $130-$323 range depending on condition and whether they've been serviced. Blown or tired tweeters are the usual reason a pair gets parted out. Crossover networks with level controls are sold separately as parts, and aftermarket grilles with new metal baskets and frames are available in a range of fabric colors.

Foam surround deterioration is the maintenance item collectors watch for. Restoration videos routinely reference "fresh foam" work, and sellers advertise units as professionally serviced and tested. Buyers should confirm the surrounds have been replaced or are sound, check that both level controls move cleanly, and verify the tweeters are original or properly serviced.