JBL 2355 Bi-Radial Horn
Little is documented about the JBL 2355 in official literature. What survives comes mostly from owner accounts, not factory spec sheets. The record shows a cast aluminum horn lens with a large rectangular mouth, built around the JBL 2345 bi-radial horn. It was the centerpiece of JBL's bi-radial horn family - the constant-directivity design that emerged in the late 1970s, refined through digital computer techniques. The bi-radial approach controls horizontal and vertical dispersion separately. The 2355 offers 110° H × 60° V dispersion with constant directivity above the crossover frequency.
The 2355 was intended for professional studio monitoring, as seen in period house sound system reports (DB Magazine, August 1982, p.40). It's a large-format horn with a 2-inch throat, going from a circular throat to a rectangular mouth. It's designed to be mounted vertically, long axis of the mouth vertical, for best imaging. In a typical two-way system it pairs with a 15" woofer in a small enclosure of about 3 cubic feet, crossed over at 1200 Hz with a 12 dB/octave slope. The JBL 2445 2" compression driver is a commonly recommended match.
Owners describe the 2355 as fantastic-sounding and easy to live with, with superb imaging and wide, even dispersion. The controlled vertical dispersion is a real benefit in a room, keeping floor and ceiling reflections down. But it's not a polite speaker. The 2355 has a strong presence region. JBL's studio monitors of that era were voiced to be neutral, not flattering, and some people may find that aggressive. It also won't do "warmth" in the mid-fi sense. The horns are huge, so getting them to look at home in a living room takes custom work.
Pairs do pop up on eBay, and relatively inexpensively for a large-format JBL horn - "for a song," as one owner put it. Budget for a new or custom-built crossover, and expect to refoam the paired woofers, a typical repair for drivers of that era. The horn itself, being cast aluminum, doesn't have the foam-rot issues of the woofers it's paired with.
Known Specs
- Type: Cast aluminum horn lens, bi-radial design
- Dispersion: 110° H × 60° V
- Throat: 2-inch, circular to rectangular mouth transition
- Recommended crossover: 1200 Hz, 12 dB/octave
- Recommended driver: JBL 2445 compression driver
- Recommended enclosure: ~3 cubic feet
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