JBL 4681 (1988–1994)

The JBL 4681 is a cinema screen speaker system, made between 1988 and 1994. It belonged to JBL's professional cinema lineup, the same family as the 4682 subwoofer, which the 4681 was typically stacked on top of in theater installations. It is a two-way system. The low-frequency driver has a 160 mm (6.5 in) cone. The compression driver has a 25 mm (1 in) titanium-laminated diaphragm, an aluminum voice coil and fluid cooling. The cabinet weighs 42 kg (92.5 lb), is finished in black paint, and comes with bracket legs for mounting.

The specs from the manual are solid for a cinema box. Frequency response is 55 Hz - 18 kHz (-10 dB) and 70 Hz - 16 kHz (±4 dB). Sensitivity is 101 dB SPL (1W, 1m, 300 Hz to 4 kHz). Continuous power capacity is 200 W (800 W peak), and nominal impedance is 8 ohm. The crossover is a 4th-order Linkwitz-Riley design with high-pass and low-pass filters, a Bessel filter in the midrange, and a corrective HF network. The crossover point to the companion 4682 subwoofer was initially set at 150 Hz, later revised to 100 Hz.

The one substantial owner account on record is a Gearspace.com thread. The user calls the 4681 "a good speaker" held back by its stock crossover. The original PCB has badly routed traces that cause interaction between the HF, MF, and LF sections. It also uses Siemens electrolytic capacitors and motor-run caps, which the owner found wanting. He had new crossovers built point-to-point with film caps, using the same values. He reported the difference as "night and day," with cleaner imaging, better depth and better separation.

No original price, production quantities, or dimensions beyond weight have surfaced in the available documentation. Period classified advertisements show the broader JBL professional speaker market was active, with listings for subwoofers and high-fidelity speaker repair services (Audio, July 1977, p.118). The 4681 is known among cinema-sound collectors mainly through JBL's theater installs of the late 1980s and early 1990s, and through that single detailed owner's account of fixing its one notable weakness.

Type: Cinema ScreenSpeaker System, 2-way
Drivers: 160 mm (6.5 in) cone LF; 25 mm (1 in) titanium-laminated diaphragm HF with fluid cooling
Frequency response: 55 Hz – 18 kHz (-10 dB); 70 Hz – 16 kHz (±4 dB)
Sensitivity: 101 dB SPL (1W, 1m, 300 Hz – 4 kHz)
Power capacity: 200 W continuous (800 W peak)
Impedance: 8 ohms
Crossover: 4th-order Linkwitz-Riley, with Bessel midrange and corrective HF network
Weight: 42 kg (92.5 lb)
Finish: Black, painted
Production: 1988–1994