Advent Large Bookshelf (1969–1977)
A no-frills, 10-inch acoustic suspension speaker that delivers deep bass with surprising power on modest amplification.
Overview
The Advent Large Bookshelf came out in 1970 as "The Advent Loudspeaker" and was renamed later to tell it apart from a smaller model. It is a heavy, two-way sealed speaker built for impact rather than looks. Each cabinet weighs 38 pounds and measures 18.5 × 11.5 × 10.5 inches. Inside is a 10-inch woofer with a Masonite cone, mounted in a 12-inch basket and suspended by foam surrounds, plus a 1-inch "fried egg" dome-in-dome tweeter. The design goes for bass extension, down to 45 Hz, in a compact 1.8 cubic foot sealed enclosure. It presents an 8-ohm load and runs fine on as little as 20 watts, though it benefits from more power for tighter control.
Two cabinet styles were offered. One is a walnut-veneered version with a bullnose front edge. The other, more common one is a utility model with a flat baffle and vinyl wrap. Both use identical drivers and crossover topology. A switch on the rear panel boosts high-frequency output by 2 dB, so you can adjust the tone a bit for the room. The fabric-covered foam grills attach through plastic frames with spacers, and connections go through single screw-type binding posts.
Design
The woofer's Masonite cone and sunken mounting ring allow more excursion, which helps low-frequency output without porting. The crossover uses a first-order filter on the tweeter and a second-order filter on the woofer. There is an air-core inductor on the woofer side and an electrolytic capacitor in the high-pass network. The parts are wired point to point, which keeps the design simple and serviceable. Early production tweeters are reported to have green domes with a slightly recessed sound, while later red-dome versions offer more presence.
Context
Henry Kloss designed the Large Bookshelf after he left Acoustic Research. The aim was acoustic suspension performance at an accessible price. At $119.95 per pair in 1970, it undercut competitors like the AR-3 and KLH Model Five while offering deeper bass and higher output. It was sold through mail order and electronics chains to budget-conscious buyers who wanted serious sound. Stereo Review (December 1971, p.87) noted its "impressive bass response and overall loudness capability for the price." The speaker gained a cult following, particularly when users found that stacking two pairs vertically made a quasi-line array - dubbed the "Double Advent" - that improved imaging and bass depth.
Market
Working pairs now sell for $150 to $400, with walnut bullnose models commanding a 30-50% premium. Foam surrounds and the electrolytic crossover capacitor degrade over time, commonly causing rattles, loss of bass, or dull high frequencies. Refoaming and recapping are essential for reliable performance, typically costing $80 - $120 per speaker. The rear HF switch often fails from corrosion or cracked solder joints. Buyers should test for buzzing at low frequencies, crackling tweeters, and binding post corrosion. Avoid models with upgraded drivers, since replacements diminish originality and resale value.
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