Altec 684A (1977–1983)
The Altec 684A model number refers to two different products. The better-known one, in enthusiast circles, is the Duplex Monitor - a large floor-stage monitor from Altec's Voice of the Theatre professional line. But period audio magazines also describe a 684A moving-coil dynamic microphone sold in the early 1960s, and the same number appears in Audio (November 1961, p.39) in a context that seems to describe a mic. Whether Altec reused the model number or the microphone was a different, earlier release is not fully documented in the sources available here. What follows is what the record shows for the speaker version.
The 684A Duplex Monitor was built from 1977 to 1983. It's a sizable stage wedge made for live-sound monitoring. It has an 18″ woofer and a 902-16A compression driver on an 811-90 horn, crossed over at 500 Hz by an N-500-8 network. It's rated at 100 watts continuous (200 watts program), with a sensitivity of 103 dB SPL at 4 feet for 1 watt. The cabinet measures 30″ × 35½″ × 24″ and weighs 118 pounds. The finish is black, and an L-pad controls the high-frequency level. The primary specs table lists impedance as 16 ohms, though an adjacent entry on the same source page says 8 ohms. The 16-ohm figure seems more consistent with the driver complement.
A related model, the 685, appears next to it in the VOTT model-number list, but no further details on that variant are recorded here. No original price, user reviews, or market values for the 684A speaker have surfaced in the available research.
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