Few speakers say 1970s like a JBL L100 with its sculpted orange foam grille. It started as a studio monitor brought home, it became JBL's most successful product of its time, and JBL kept studio and home versions on sale side by side, so listings mix up the names constantly. Here's how to tell the original L100 Century, the 1973 revision collectors call the L100A, the 4310 and the 4311 apart, and where the L36 Decade and L65 Jubal fit in.
It started in the studio
The 4310 control monitor came first. Arnold Wolf, who ran JBL from 1969 to 1979 and designed its 1967 logo, gave it a raised oval baffle that collectors call the racetrack. He put the level controls on the front, because studios hung monitors or set them on window shelves where rear controls couldn't be reached. Ed May and Bart Locanthi did engineering work on it.
Studio engineers liked their 4310s enough to take them home, and that prompted a consumer version. Sidney Harman had bought JBL in 1969, and his marketing chief Irving Stern pushed for home versions of the monitors. Stern named the result The Century. After its debut at the summer 1970 Consumer Electronics Show, Wolf said it became JBL's most successful product to date and, from all indications, the best-selling loudspeaker system of the decade.
The first L100 Century, 1970 to 1972
The original L100 used the 4310's drivers. That means a 12-inch woofer with an Alnico V magnet and a white-coated cone, the 5-inch LE5-2 midrange, and the LE20, a 2-inch direct-radiator tweeter. Wolf says it also dropped the 4310's raised baffle and its attenuators. So a 2-inch tweeter and no level controls on the front add up to a first-version L100.
The grille was Wolf's idea too. He borrowed it from microphone windscreens, and the L100 was possibly the first loudspeaker with a shaped-foam grille. JBL called the foam Sculptured Air, in a pattern named Quadrex 2. The color is painted on, because dyed foam looked dull, and each grille is one color. JBL's 1971 catalog lists Ultra Blue, Burnt Orange and Russet Brown. The cabinet is oiled walnut on all four sides so it could stand upright or lie on its side, and JBL called it a bookshelf speaker. It's ported, with a tuned port for bass efficiency.
The 1973 revision, or L100A
In 1973 JBL reworked it with a better tweeter and shifted crossover points, 1,500 and 6,000 Hz on the 1973 sheet. The new tweeter is a 1.4-inch direct radiator with a smaller cone for wider dispersion and a ring of dense foam around it. It's the same unit as the 4311's LE25. Midrange and high-frequency controls appeared on the front of the cabinet, hidden behind the removable foam grille. The midrange itself didn't change.
JBL's 1973 brochure shows the speaker as the L100A but still sells it as the "new, improved L100 Century". JBL's own model history lists L100, L100A and L100A Late Model together through 1977, and the L112 took over in 1978. The 1973 grille colors were Ultra Blue, Chocolate Brown and Burnt Orange. JBL also claimed engineers from Warner Bros. and Elektra Records compared the new L100 with their 4310s and called it a significant advance on the studio monitor. On an L100A, pull the grille. A 1.4-inch tweeter and two knobs on the baffle confirm it.
The 4311
Once the home speaker improved, studios wanted a studio version, and that became the 4311, introduced in 1973. JBL's brochure calls it acoustically equal to the new L100. It dropped the 4310's raised baffle and used the smaller tweeter and revised crossover. JBL's 1978 sheet gives its drivers as a 2213 12-inch woofer, the LE5-2 midrange and the LE25 tweeter on a 3112-A network, and rates it at 91 dB for 1 watt at 1 meter.
The 4311 looks different from an L100 at a glance. The baffle is black, the grille is black fabric, and the cabinet came in textured gray or oiled walnut. A badge reads MODEL 4311 CONTROL MONITOR, and the Presence and Brilliance knobs sit along the bottom of the baffle. A 4311 never had a foam grille, so foam on one was added later. For a while, early JBL monitors also carried a silk-screened Hollywood logo on the cabinet sides. The 4311B appears in JBL's 1979 catalog, and JBL's 4312 sheet is dated 1983.
Telling them apart fast
- 2-inch tweeter, no front controls, foam grille. The first L100 Century, 1970 to 1972.
- 1.4-inch tweeter with a foam ring, controls behind a foam grille. The revised L100 Century, or L100A, 1973 to 1977.
- Raised oval baffle with controls on the front. A 4310.
- Black baffle, black cloth grille, model badge, knobs along the bottom. A 4311, in walnut or gray.
Drivers tell you the rest. JBL describes the L100 woofer's cone coating as white, so a cone that isn't suggests a replacement. On a 4311, the 2213, LE5-2 and LE25 labels should all be there.
The L36 Decade
JBL launched the Decade line in 1974 to reach buyers on smaller budgets and sold it with a boxing theme. The L16 was The Welterweight, the L26 The Middleweight and the L36 The Heavy Weight, at 38 lb. JBL called the L36 the first JBL three-way designed to sell at a moderate price. It uses a 10-inch long-excursion woofer with an Alnico V magnet, a 5-inch midrange with a thin aluminum center dome, and the same 1.4-inch tweeter as the L100 and 4311, crossed at the same 1,500 and 6,000 Hz.
The L36 is easy to spot. Its cabinet is natural oak, oiled, with a ducted port through the baffle and a stretch-fabric grille in orange, blue or brown. All Decade networks have continuously variable controls. JBL listed it as L36 and L36A from about 1974 to 1977. JBL also claimed buyers took home more than 100,000 of the L26, the original Decade, in its first year.
The L65 Jubal
The L65 Jubal is the compact floor-standing sibling, 24½ inches tall with a smoked-glass top. JBL built it around the 077 ring radiator, a high-frequency driver that had only been used in professional systems. It's horn-loaded, with a die-cast aluminum horn and a clear acrylic dispersion element, and JBL claimed 130 degrees of horizontal dispersion at 15,000 Hz. Below it are a 5-inch cone midrange and a 12-inch Alnico V woofer with a die-cast ring on the voice-coil former that adds mass at the coil. JBL filed a patent on that ring. The crossovers sit at 1,000 and 6,500 Hz, the box is ported, and the grille came in Midnight Blue, Earth Brown or Rust Red stretch fabric over oiled walnut.
JBL listed it as L65, L65A and L65B from about 1974 to 1979. Its brochure is styled after Leonardo da Vinci's notebooks, sepia sketches and mirror writing included. On a used pair, check that the glass top is there and unchipped and that the acrylic element in the 077 horn is present and whole.
Which one we'd buy
If you want the look, buy an L100 with soft, intact original foam grilles, since the grille is half the reason people want one. A first-version pair is the rarer history piece, and a 1973-on pair gives you the level controls. If you'd rather not worry about foam, a 4311 has the same acoustic recipe behind a cloth grille. JBL said the L100 works with as little as 10 watts RMS and named up to 150 watts RMS as optimum, so most amps will do. Our amp matching guide explains JBL's old sensitivity ratings. See everything from JBL, or browse the speakers we track.