JBL · Bookshelf · c.1973–1979 (4311B into the early 1980s)
JBL's studio monitors were the source of the L100, and the 4311 is the studio side of the same speaker. Arnold Wolf designed the earlier 4310 with a raised racetrack baffle and put the level controls on the front, because a monitor hung on a wall or set in a window shelf had controls nobody could reach at the back. When JBL improved the L100 in 1973, studios asked for a version of it, and the 4311 dropped the raised baffle and used the L100's smaller 1.4-inch tweeter. JBL called the two acoustically equal. The drivers are a 12-inch 2213 woofer, the LE5-2 midrange and the LE25 tweeter on a 3112-A network, with Presence and Brilliance knobs along the bottom of a black baffle and a MODEL 4311 CONTROL MONITOR badge. It came in oiled walnut or textured gray with a black cloth grille, and the 4311B followed around 1979.
With the grille off
Ask for a photo of every driver with the grilles off, on both speakers. They should match each other and this list.
Check the drivers against the original part numbers, since drivers get swapped over 50 years of use. The front Presence and Brilliance controls can crackle with age.
New to old speakers? How to check a used pair walks through every driver, the crossover and the cabinet.
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