Altec 511B Horn

At 8 lbs and just over a foot wide, it’s a compact beast of focused projection—cast aluminum with vanes that slice sound into precision.

Overview

The Altec 511B horn isn’t one of those ornate, flared antiques that dominate vintage speaker porn. It’s industrial—a sectoral horn cast from aluminum, built for purpose, not display. Its shape is angular, almost utilitarian, with internal vanes dividing the acoustic path into distinct sections. That division is key: it’s not a multi-cell design, but a single horn segmented to control dispersion. Measuring 11.5" wide, 8.5" high, and 9.5" deep, it occupies space like a compact monitor, but with the heft of serious engineering—8 lbs of dense, vibration-resistant metal.

Designed for the mid or high-frequency section in two-way or three-way systems, the 511B slots into builds where clarity and directionality matter. The 1" throat suggests driver compatibility with common vintage compression units, and indeed, sources recommend pairing it with Altec’s own 902, 908, or 731C drivers. While some users report running it as a midrange with a Selenium 250, others emphasize staying above 800 Hz for safe operation—despite some conflicting suggestions of 500 Hz in secondary sources. The consensus among Altec enthusiasts, however, points to 800 Hz as the reliable lower limit.

Owners appreciate its focused output. One builder using FaitalPro drivers claimed it produced “the most natural sound I have heard from any system,” later buying a second pair with top-tier drivers. That kind of testimony speaks to its potential when matched correctly. It’s not just a relic—vintage Altec horns like the 511B remain desirable for both PA applications and high-end home stereo mods. They’re not rare in the sense of being mythical, but clean, unblemished units are noteworthy. A recent listing described a pair as “pristine, as new 9/10,” though even NOS examples from old live sound inventories can carry warehouse scratches—cosmetic scars from decades in storage, not use.

Specifications

Key Features

Sectoral Horn with Internal Vanes

Unlike multi-cell horns that use separate chambers to tame breakup and dispersion, the 511B is a single cast structure with vanes that subdivide the horn path. This sectoral approach allows for controlled directivity without the complexity of multiple cells. It’s a simpler, more robust design—suited for environments where reliability trumps cosmetic refinement.

Cast Aluminum Construction

The entire horn, including the flange, is cast aluminum—lightweight yet rigid. This material choice reduces resonance and supports clean high-frequency reproduction. The 1/4" thick flange adds structural integrity, ensuring a secure seal between driver and horn throat, which is critical for efficient coupling and avoiding air leaks that degrade output.

Front-Mounting Flange with Standardized Tapped Holes

Mounting is handled via four 1/4-20 tapped holes spaced on 10" centers across the front flange. This configuration simplifies integration into cabinets or enclosures, allowing secure attachment from the front—a practical feature for both permanent installations and modular builds. The front-mount design also makes driver servicing more accessible compared to rear-loaded setups.

1" Throat for Standard Compression Drivers

The 1" throat opening aligns with a wide range of vintage and modern compression drivers. Compatibility includes the Altec 902 and 908 series, as well as the 731C high-frequency driver. This flexibility makes the 511B a viable candidate for restoration projects or custom speaker builds where sourcing exact original components might be difficult.

90° x 40° Dispersion Pattern

The horn projects sound with a 90-degree horizontal and 40-degree vertical dispersion. This asymmetric pattern suits applications where wide lateral coverage is needed but vertical spread must be limited—common in PA setups or near-field monitoring. The focused vertical dispersion helps reduce ceiling and floor reflections, contributing to cleaner sound in reflective environments.

800 Hz Recommended Crossover Frequency

The documented crossover recommendation is 800 Hz. While some sources suggest operation as low as 500 Hz, user reports and enthusiast consensus indicate that 800 Hz is the safer lower limit. Running it below this point risks over-excursion and distortion, particularly when paired with high-output drivers. Builders are advised to respect this threshold unless using specific driver combinations rated for lower loading.

Collectibility & Value

These horns remain in demand among DIY audio builders and PA restorers. A used pair was listed in a private forum for $350 AUD, described as “pristine, as new 9/10,” indicating strong secondary market interest even for non-NOS units. Another example, listed as “* SOLD *,” was described as NOS—never installed, with no driver ever attached—but showed handling scratches from warehouse storage. Condition clearly affects value, but even cosmetically imperfect units hold appeal due to their performance potential. No original pricing or production years are documented, but their continued use in high-performance builds underscores lasting utility over mere nostalgia.

eBay Listings

As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.

Related Models

• Altec 311
• Altec 402A
• Altec 811b