JBL 4315A (1974)
The 4315A is one of JBL's most famous studio monitors. It sits between the 4311 and 4313 in the professional line. It was introduced in 1974 as part of the Studio Monitors catalog for 1974/75, and the "A" suffix marks a revision of the original 4315. It was aimed squarely at professional studio use, and collectors still regard it as one of the most accurate speakers of its era.
The driver lineup is where the 4315A gets interesting. It uses a pair of 220mm (8-inch) 124H cone woofers, a single 220mm 110-2 midrange driver, and a 2405 dome tweeter. The cabinet is bass-reflex, tuned to roughly 45Hz. Crossover points are 320Hz and 3.3kHz, with a 12dB/octave slope on the midrange. Frequency response is rated at 45Hz - 20kHz ±3dB, sensitivity at 90dB SPL 1W/1m, and nominal impedance at 8Ω. Power handling is 60W. The cabinet measures 606 × 370 × 210mm and weighs 18.2kg.
The sources disagree on whether this is a 2-way or 3-way system. Lansing Heritage and weltron.de call it 2-way. The Stereo Lab describes it as a 3-way bass reflex. With a dedicated midrange driver and two crossover points on the spec sheet, the 3-way description looks more accurate.
Studio Sound (February 1978, p.16) carried an advertisement from R.D.G. Audio Visual Ltd. listing the 4315A among professional studio equipment available at the time.
Original pricing is uncertain - sources list both $650 and $400 - and no production end year is documented. On the vintage market today, a good pair typically sells in the $500 - $1000 range.
Known Specs
- Woofers: 2 × 220mm (124H cone)
- Midrange: 220mm (110-2 cone)
- Tweeter: 2405 dome
- Crossover: 320Hz, 3.3kHz
- Frequency response: 45Hz–20kHz ±3dB
- Impedance: 8Ω
- Sensitivity: 90dB 1W/1m
- Power handling: 60W
- Dimensions: 606 × 370 × 210mm
- Weight: 18.2kg
Common restoration issues include foam surround rot on the 124H woofers and the 110-2 midrange, and the 2405 tweeter losing ferrofluid in the voice coil gap. Recapping the crossover is also recommended, since the original capacitors drift out of tolerance.
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