JBL 2312 HF Crossover Card (1970s–1980s)

The JBL 2312 is not a standalone piece of gear — it’s a plug-in crossover card, specifically the high-frequency output module for the JBL 5234A and 5235 electronic crossover units used in professional studio and cinema systems from the 1970s and 1980s. If you owned a 5235, you’d slot in the appropriate 2312 card to set the crossover point for your high-frequency drivers in a bi-amp or tri-amp setup. The card itself is frequency-specific at purchase — you chose from variants at 2000, 2500, 3200, 4000, 5000, 6300, 8000, 10000, or 12500 Hz — and there are no user-adjustable controls on the board. It’s a passive PCB with a card-edge connector, nothing more.

The 2312 was part of a family of cards for these crossover chassis: the 2310 served the low-frequency band and the 2311 handled bandpass/low-mid duties, with the 2312 covering HF. A 1981 Recording-Engineer article (Aug 1981, p.46) describing a club sound system’s front fills lists a JBL 2312 alongside a 2308 slant plate lens and 2420 driver, confirming the card’s role in real-world JBL professional installations of the period.

Surviving documentation on the 2312 is thin. No production years, original retail price, frequency response, or THD figures are recorded for the card itself — only its crossover frequency options and chassis compatibility. What the user community has established: aging electrolytic capacitors on these cards drift out of spec, which can make the HF harsh or drop output level. The standard repair is recapping the electrolytics, and some owners replace them with film caps for reliability. Used cards surface periodically on eBay and Reverb, typically $25–$75 depending on frequency variant and condition.

Type: Plug-in HF crossover card for JBL 5234A / 5235 active crossovers
Available crossover frequencies: 2000, 2500, 3200, 4000, 5000, 6300, 8000, 10000, 12500 Hz (frequency-specific, not adjustable)
Connector: Card-edge / plug-in, compatible with 5234A and 5235 chassis
Construction: Passive PCB, no user controls
Known issue: Aging electrolytic capacitors cause HF harshness or level drop; recapping is the standard fix