Altec 311 (Late 1940s)

At 30 lbs and clad in gray wrinkle finish, this cast aluminum horn is a plain, no-nonsense sectoral design.

Overview

The Altec 311 isn't subtle. It's a sectoral horn built for presence, made to cut through ambient noise in movie theaters, recording studios, and public address systems where clarity and projection were required. Introduced in the late 1940s, it became a core component of Altec's "Voice of the Theatre" (VOTT) speaker systems. At 20 inches wide and 30 lbs, the 311 takes up real space. Its cast aluminum body is coated with "Aquaplas" to dampen unwanted resonance. It was built for volume, efficiency, and reach, and 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 comes with the sectoral horn design and isn't a flaw. In the right system, with proper bass support, it delivers a vintage clarity that modern horns often struggle to replicate.

Specifications

Manufacturer	Altec
Product type	Horn
Dimensions	20" wide x 11" high x 13" deep
Weight	30 lbs
Frequency Response	500 Hz to 16,000 Hz
Crossover Frequency	500 Hz
Flare Rate	Exponential
Throat Diameter	1"
Dispersion pattern	90° horizontal by 40° vertical
Material	Cast aluminum
Coating	Coated with "Aquaplas" to reduce ringing
Finish	Gray wrinkle
Driver compatibility	Made to be used with the Altec series of 1.4" compression drivers. Accepts any Altec 1.4" Driver with a 3-bolt pattern.

Key Features

Two-Piece Cast Aluminum Construction

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

Sectoral Multicell Design with Exponential Flare

Unlike radial or conical horns, the 311 uses a sectoral, multicell design that divides the sound wave into multiple channels before release. Dispersion is tightly controlled - 90° horizontal by 40° vertical in the standard configuration - and the exponential flare rate gives smooth impedance matching from throat to mouth. The design favors directivity and efficiency over wide dispersion, which suits focused listening zones in large rooms or venues.

Driver Interface for 1.4" Compression Drivers

Despite a 1" throat diameter, the 311 accepts Altec's 1.4" compression drivers via a standard 3-bolt mounting pattern. That compatibility with the 802/806/807 series drivers made it a flexible part of the VOTT lineup. Vintage units often need replacement gaskets at this interface, as the original seals degrade over time and can cause air leaks and lost efficiency.

Variants with Adjusted Dispersion Patterns

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 keeping 40° vertical, which suits longer throw applications. The 311-90 keeps the wide 90° horizontal spread and 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 used in larger enclosures like the A-4 and A-7, where it handled high frequencies with unmatched efficiency for its time. Its use in movie theaters and recording studios built its reputation as a professional-grade component that put reliability and sonic impact ahead of domestic refinement.

Collectibility & Value

Today, the Altec 311 is sought after by restorers and vintage audio enthusiasts rebuilding VOTT systems. Condition matters. 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 the original "Aquaplas" coating may degrade, affecting acoustic performance. Replacement gaskets are frequently needed for 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, such as scratches and paint chips, are valued if structurally intact and free of dents or cracks.