JBL 4331A / 4331AWX (1976)
The JBL 4331A is a large-format, 2-way studio monitor from the professional 43xx series. It came out in 1976 as a refinement of the earlier 4320. It uses a 38cm (15-inch) 2231A cone woofer and a horn-loaded high-frequency section: the 2420 compression driver, the 2312 exponential horn and the 2308 acoustic lens. The slotted lens gives these monitors their recognizable front face. The crossover sits at 800 Hz. Output is rated at 93 dB (New JIS) into 8 ohms.
There were two cosmetic variants. The 4331A has a gray painted cabinet with a black grille. The 4331AWX is finished in walnut veneer with a blue grille. Both use the same 156-liter bass reflex enclosure. JBL rated it as "bookshelf type" only in the loosest sense, since it weighs 57 kg and measures 619 x 778 x 497 mm. The cabinet has iron reinforcing fittings so the speakers can be suspended. The acoustic lens can be rotated, so the speaker works in either vertical or horizontal orientation. A rear switch lets the 4331A run through the internal network or as a 2-channel bi-amped system.
The 4331A was priced at ¥380,000 per unit around 1978. The walnut 4331AWX was slightly higher at ¥395,000. Frequency response is specified at 35 Hz to 15 kHz ± 3 dB, with directional coverage of 60° x 30° at 12 kHz. Power handling is 75W below 800 Hz and 30W above. The network itself is rated at 75W.
Documentation on this model is mostly limited to period Japanese catalog listings. The Japanese reference site jblfan.mitsu-hide.com notes that the 4331A is fairly often seen in good condition on Yahoo Auctions and used shops. A Japanese buyout reference price of ¥90,000 appears in trade listings. An Australian classified listing for a pair of ex-ABC Studios 4331As confirms the driver complement (2231A woofers, 2420 drivers, 2312 horns, 3131A crossovers) and notes all original diaphragms and cone assemblies. No period reviews have surfaced in the available documentation.
Known specifications
- Type: 2-way, 2-speaker, bass reflex, bookshelf type
- Woofer: 38cm cone (2231A)
- High-frequency: Horn type (2308 acoustic lens + 2312 horn + 2420 driver)
- Crossover: 800 Hz
- Frequency response: 35 Hz – 15 kHz ± 3 dB
- Impedance: 8 Ω
- Output: 93 dB (New JIS)
- Power handling: 75W (below 800 Hz), 30W (above 800 Hz)
- Enclosure volume: 156 L
- Dimensions: 619 x 778 x 497 mm (W x H x D)
- Weight: 57 kg
- Finish: 4331A gray/black grille; 4331AWX walnut/blue grille
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