Altec 811B

Name: Altec 811b
Brand: Altec

A cast aluminum sectoral horn that put the "Altec sound" in everything from Voice of the Theatre installations to the Valencia. It still turns up in pairs, green-painted and bolted to 806s.

Overview

The Altec 811B is a sectoral horn. It is a cast aluminum high-frequency component that bolts onto Altec's 1" compression drivers and throws their output in a specified 90° horizontal by 40° vertical pattern. It's the smaller, more domestic sibling of the big multicell horns. Collectors most often find it paired with an 806 or 802 driver, sometimes still attached to the cabinet it shipped in. Altec built it in the United States. One documented 806-8A plus 811B pairing is dated to the 1973-1976 window, though the horn itself appears across a longer span of Altec catalogs and consumer systems.

The design brief is simple: controlled dispersion and efficient projection from a rigid casting that resists resonance. The horn uses exponential expansion to reach its rated coverage. The cast aluminum body is why these things survive decades of PA duty with nothing worse than chipped paint. Owners call the sound the "distinctive Altec sound" - clear, detailed and dynamically alive. They also say it can turn shouty or honky when the driver match or the EQ is wrong. The 811B rewards careful pairing and punishes laziness.

The horn has a documented measurement record. Joseph Crowe published measurements of an 811B fitted with a TAD TD-2001 driver (1.7 ms gate, 1.5 m mic distance). The step response took an unusually long 9.5 milliseconds to settle, so the lively character comes with some time-domain baggage. High Fidelity (July 1955, p.27) was already pitching the H-811B as part of a build-your-own system with the 802C driver and 803A woofer, advertising a guaranteed range out to 22,000 cycles when mounted in a proper enclosure. That's marketing copy, not a lab verdict.

Key Features

90° x 40° Sectoral Coverage

The 811B's defining number is its dispersion: 90° horizontal by 40° vertical. That gives enough horizontal spread to cover a room or a theater seating block, with a tighter vertical window that keeps energy off the floor and ceiling. Altec's own catalog copy from the period describes the high-frequency horns as sectoral, exponential types built for uniform control of the projection angle, and the 811B fits that description. Collectors note the pattern makes placement forgiving in the horizontal plane but demands some attention to listening height.

Exponential Expansion in Cast Aluminum

The flare is exponential, the classic way to match a compression driver's throat impedance to free air smoothly across the passband. The body is cast aluminum rather than stamped steel or molded plastic. It's heavy enough to resist panel resonance and rigid enough that the horn doesn't add its own color under drive. The trade-off is cosmetic: cast aluminum chips and corrodes, and the green factory finish on many examples is now a patina rather than a paint job. Late in the 811/511 production run, just before Altec closed its Anaheim factory, the company began coating horns with Aquaplas at the factory to address a resonance issue. A poster who identifies as a former Altec engineer reported this. Earlier units left the factory without it.

Driver Compatibility Across the Altec Line

The 811B is designed for Altec's 1" high-frequency compression drivers. The 802, 806, 807, 808, and 902 series all bolt up. In period Altec literature the 811B is specified for use with the 802D or 806A driver. Component-matching charts from the mid-1970s pair it with the N801-8D dividing network and recommend the 806-8A, with the 802-8D as the alternate. One hobbyist's documented setup crosses the horn at 500 Hz or higher, and a 25 mm throat diameter is reported for the driver interface. Nearly any Altec 1" driver in the family will work, which is a large part of why these horns remain in circulation.

Crossover Options at 500 Hz or 800 Hz

Altec's own materials list the 811B's low-frequency limit at 800 Hz. The horn is typically used with either a 500 Hz or 800 Hz crossover depending on the driver and system, so it shows up in a 500 Hz network in one installation and an 800 Hz N-800-E in another. Owners report that pushing the crossover lower than the driver wants is where the honky reputation comes from. Used within its limits, the 811B is clean and quick. The 511B, its larger stablemate, is said by some users to cross over lower still. That's a forum impression, not a published spec.

Historical Context

The 811B's main job is as a building block. It forms part of the Altec A7 speaker system when paired with the 802-8D driver and 416-8 woofer. It was also used in the Altec Lansing Valencia consumer speaker, paired with the 806 compression driver. Altec's own catalog copy from the period lists the 811B among the components inside the 831A Capistrano system, alongside the 803B woofer and 802D driver. The horn is primarily recognized as a component in larger systems like the 820C Corner Speaker System, the kind of installation where a theater or auditorium needed efficient, controlled high-frequency projection from a compact package.

Production dates for the horn alone aren't documented in the public record. One 806-8A plus 811B combination is dated 1973-1976 and noted as made in the USA. The late-run Aquaplas coating points to production continuing into the final years before the Anaheim factory closed.

Collectibility & Value

The 811B is highly sought after by vintage audio enthusiasts and collectors. One cited eBay range for the horn and driver runs from $160 to $1,600. Current listings show the spread: a pair of 806-8A drivers on H-811B horns at $750, a pair of H811B horns pulled for a Heathkit build at $999, a single 802D and 811B combination at $583, and a complete A7-500 Voice of the Theatre system with 416A, 802D, H-811B, and N-800-E at $13,000. That last figure is a whole system, not the horn.

Buying advice from the field: check the mounting bolts first. Seized or stripped bolts are a common problem on these castings, and a snapped fastener in a forty-year-old aluminum flange is a bad afternoon. Replacement gaskets for the driver throat are recommended for proper sealing. Any horn that's been separated from its driver should be inspected for a hardened or missing gasket before bolting up. Cosmetic condition varies widely. Clean original pairs command a premium, but the green factory finish and cast surface mean even well-used examples can be made presentable. Some owners have gone further, stripping the fixing flange and applying Dynamat damping, or discussing anodizing and chroming the aluminum. Those are aftermarket practices, not factory spec, and they change the collector value accordingly.