Altec 311 (Late 1940s)

At 30 lbs and clad in gray wrinkle finish, this cast aluminum horn means business—projecting sound with the unapologetic efficiency only true sectoral design delivers.

Overview

The Altec 311 isn’t subtle. It’s a sectoral horn engineered for presence, built to cut through ambient noise in movie theaters, recording studios, and public address systems where clarity and projection were non-negotiable. Introduced in the late 1940s, it became a core component of Altec’s legendary "Voice of the Theatre" (VOTT) speaker systems—installations that defined professional sound reinforcement for decades. At 20 inches wide and weighing 30 lbs, the 311 commands physical space as much as sonic territory, its cast aluminum body coated with "Aquaplas" to dampen unwanted resonance. This isn’t a horn designed for polite listening; it’s a tool built for volume, efficiency, and reach, optimized to work with Altec’s 802, 806, and 807 series compression drivers. Owners report a sound that’s big, bold, and dynamically charged—some describe it as "forward" or even "shouty" on certain material, but that character is baked into the sectoral horn design, not a flaw. It’s a sound that demands attention, and in the right system, with proper bass support, it delivers a vintage clarity that modern horns often struggle to replicate.

Specifications

Key Features

Two-Piece Cast Aluminum Construction

The Altec 311 is a two-piece assembly—throat section and flare section—poured from cast aluminum, a method chosen for rigidity and mass. This construction minimizes panel resonance, a common issue in lighter horn materials, while the entire body is treated with a proprietary "Aquaplas" coating designed to further reduce internal ringing. The result is a horn that stays acoustically neutral under high drive levels, preserving transient detail even at high output.

Sectoral Multicell Design with Exponential Flare

Unlike radial or conical horns, the 311 employs a sectoral, multicell design that divides the sound wave into multiple channels before release. This controls dispersion with surgical precision—90° horizontal by 40° vertical in the standard configuration—while the exponential flare rate ensures smooth impedance matching from throat to mouth. The design prioritizes directivity and efficiency over wide dispersion, making it ideal for focused listening zones in large rooms or venues.

Driver Interface for 1.4" Compression Drivers

Despite a 1" throat diameter, the 311 is engineered to accept Altec’s 1.4" compression drivers via a standard 3-bolt mounting pattern. This compatibility with the 802/806/807 series drivers made it a flexible component within the VOTT ecosystem. The interface often requires replacement gaskets in vintage units, as the original seals degrade over time, potentially leading to air leaks and loss of efficiency.

Variants with Adjusted Dispersion Patterns

While the base 311 model offers 90° horizontal coverage, variants such as the 311-60 and 311-90 were produced with modified cell structures to alter dispersion. The 311-60 narrows horizontal coverage to 60° while maintaining 40° vertical, ideal for longer throw applications. The 311-90 retains the wide 90° horizontal spread but is documented with the same 40° vertical dispersion, suggesting a refinement rather than a radical redesign.

Historical Context

The Altec 311 emerged in the late 1940s as a cornerstone of Altec’s "Voice of the Theatre" series, a line engineered to bring high-fidelity sound to commercial venues when few systems could. It was integrated into larger enclosures like the A-4 and A-7, where it handled high frequencies with unmatched efficiency for its time. Its deployment in movie theaters and recording studios cemented its reputation as a professional-grade component, one that prioritized reliability and sonic impact over domestic refinement. The horn’s design philosophy reflected Altec’s engineering ethos: robust, serviceable, and sonically assertive.

Collectibility & Value

Today, the Altec 311 is a sought-after component for restorers and vintage audio enthusiasts aiming to rebuild authentic VOTT systems. Condition is critical—common issues include damaged mounting flanges, stripped threads on driver studs, and corrosion or pitting in the cast aluminum, especially in units exposed to humidity. The gray wrinkle finish often chips or flakes with age, and original "Aquaplas" coating may degrade, affecting acoustic performance. Replacement gaskets are frequently needed to ensure an airtight seal between driver and horn. Market prices vary significantly by model and condition: a single used Altec 311-60 sold for ¥72,545 in December 2025, while a pair of 311-90s reached $1,800 in the same period. New old stock pairs have listed for $1,088 plus shipping, and complete setups with drivers have seen auction bids exceeding ¥398,000. Collectors note that even units with cosmetic wear—scratches, paint chips—are valued if structurally intact and free of dents or cracks.

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Related Models

• Altec 402A
• Altec 511B horn
• Altec 811b