Vintage Altec Horns Overview and Specifications

February 3, 2026

The development of high-fidelity sound reproduction in the twentieth century owes a significant debt to the innovations of the Altec Lansing Corporation. Emerging from the reorganization of Western Electric's Electrical Research Products, Inc. (ERPI), Altec Lansing established a dominant position in the cinema and professional audio industries.[1] The core of their reputation rested upon their high-frequency horns and compression drivers, which were designed to deliver exceptional efficiency, precise directivity, and rugged durability.[2] This report provides an exhaustive analysis of vintage Altec horns and brackets, synthesizing technical specifications, historical context, and mechanical interface requirements.The Historical Foundations of Altec Acoustic Engineering

The Altec Lansing story began in 1937 when the Altec Service Company was formed to maintain theater sound systems previously serviced by Western Electric.[1] In 1941, the acquisition of the Lansing Manufacturing Company led to the formation of the Altec Lansing Corporation, combining the service expertise of the former with the manufacturing prowess of James B. Lansing.[1] This synergy resulted in the "Voice of the Theatre" (VOTT) series, which became the global standard for cinema sound.[1]

The VOTT systems, such as the A-1, A-2, A-4, and A-5, were designed to provide high sound pressure levels in large environments using the limited amplifier power of the era.[1] Central to these systems were high-frequency horns, which were categorized primarily into multicellular and sectoral designs.[2] Multicellular horns, like the 1505B, were constructed from individual exponential cells to provide extremely precise control over vertical and horizontal distribution.[2] Sectoral horns, such as the 511B and 811B, utilized a cast aluminum construction with internal vanes to achieve uniform dispersion patterns.[2]Technical Principles of Horn Design and Dispersion

The primary function of a high-frequency horn is to match the high acoustic impedance of a small compression driver diaphragm to the low acoustic impedance of the surrounding air. This impedance matching is achieved through a controlled expansion of the horn's cross-sectional area. The rate of expansion determines the horn's cutoff frequency ($f_c$), below which the horn ceases to provide effective loading for the driver.

For an exponential horn, the area A(x) at a distance x from the throat is given by the formula:

A(x) = A_t * e^(mx)

where A_t is the throat area and m is the flare constant. Altec horns were meticulously designed to adhere to specific flare constants, ensuring that their stated crossover frequencies (typically 500 Hz, 800 Hz, or 1200 Hz) were supported by adequate acoustic loading.[5]Multicellular vs. Sectoral Paradigms

Multicellular horns were favored for the largest installations because they could maintain directivity at lower frequencies than smaller sectoral designs.[2] By combining multiple cells, the designer could tailor the coverage pattern by varying the number of horizontal and vertical rows. For example, the 1005B utilized two rows of five cells each (2x5) to provide a 50° horizontal by 20° vertical distribution.[3]

Sectoral horns, while generally more compact, were engineered for horizontal dispersion uniformity and high-frequency projection.[2] Models like the 311-60 and 311-90 were constructed from heavy cast aluminum and treated with Aquaplas, a damping compound intended to prevent metallic resonance.[6] These horns were ideal for wide-range two-way systems where demanding music reproduction or sound reinforcement was required.[2]Comprehensive Horn Specifications and Performance Data

The following table synthesizes the primary specifications for vintage Altec horns as identified in historical technical literature and catalog data.

Table 1: Vintage Altec Horn Specifications Overview

Horn Model	Type	Nominal Distribution (V x H)	Cutoff Frequency (fc)	Required Throat Adapter	Dimensions (Inches)	Weight
203B	Multicell	$20^\circ \times 40^\circ$	$300\text{ Hz}$	None	$32 \times 17 \times 31$	$22\text{ lbs}$
311-60	Sectoral	$40^\circ \times 60^\circ$	$300\text{ Hz}$	None	$19\frac{1}{2} \times 10 \times 21$	$19.5\text{ lbs}$
311-90	Sectoral	$40^\circ \times 90^\circ$	$300\text{ Hz}$	None	$29\frac{1}{2} \times 12\frac{3}{4} \times 16\frac{3}{4}$	$29\text{ lbs}$
803B	Multicell	$35^\circ \times 70^\circ$	$300\text{ Hz}$	30162	$26\frac{1}{2} \times 16\frac{3}{4} \times 16\frac{1}{2}$	$27\text{ lbs}$
805B	Multicell	$40^\circ \times 80^\circ$	$500\text{ Hz}$	30162	$17\frac{1}{2} \times 24\frac{3}{8} \times 13\frac{3}{8}$	$17\text{ lbs}$
1003B	Multicell (2x5)	$35^\circ \times 90^\circ$	$300\text{ Hz}$	30210 / 30170	$25\frac{1}{4} \times 38 \times 16\frac{1}{4}$	$32\text{ lbs}$
1005B	Multicell (2x5)	$40^\circ \times 100^\circ$	$500\text{ Hz}$	30210 / 30170	$25\frac{1}{2} \times 30 \times 13$	$20\text{ lbs}$
1505B	Multicell (3x5)	$60^\circ \times 105^\circ$	$500\text{ Hz}$	30166 / 30172	$16\frac{3}{4} \times 30\frac{3}{8} \times 18\frac{1}{2}$	$22\text{ lbs}$
32B	Sectoral	$40^\circ \times 90^\circ$	$800\text{ Hz}$	None	$16 \times 8 \times 8\frac{3}{4}$	$10\text{ lbs}$
511A	Paging/Sectoral	$40^\circ \times 90^\circ$	$500\text{ Hz}$	None	$23\frac{1}{4} \times 18\frac{1}{2} \times 17\frac{3}{4}$	$20\text{ lbs}$
511E	Sectoral	$40^\circ \times 90^\circ$	$500\text{ Hz}$	None	$25\frac{5}{16} \times 16\frac{3}{4} \times 17\frac{3}{4}$	$20\text{ lbs}$
31A	Paging/Sectoral	$40^\circ \times 120^\circ$	$300\text{ Hz}$	27A	$23 \times 17 \times 14$	$15\text{ lbs}$
511B	Sectoral	$40^\circ \times 90^\circ$	$500\text{ Hz}$	None	$23\frac{3}{8} \times 10\frac{5}{8} \times 11\frac{3}{8}$	$12.25\text{ lbs}$
811B	Sectoral	$40^\circ \times 90^\circ$	$800\text{ Hz}$	None	$18\frac{5}{8} \times 8\frac{5}{8} \times 13\frac{3}{8}$	$9\text{ lbs}$

The distribution patterns listed above indicate the angular coverage at the -6 dB points. Sectoral horns like the 511B and 811B were designed to provide a 90° horizontal spread, which was suitable for most auditorium and theater environments.[4] The 311-60 offered a narrower 60° horizontal dispersion, which resulted in higher on-axis sensitivity and improved imaging in certain acoustic spaces.[6]

The 203B represents an extreme case of directivity, providing a very narrow 40° horizontal and 20° vertical pattern.[10] This horn was particularly useful in deep, narrow venues or in arrays where multiple horns were stacked to cover specific zones without excessive overlap.[9] Its ability to maintain loading down to 300 Hz made it highly desirable for high-fidelity applications where a low crossover point was required to minimize the strain on large woofers.[5]Throat Adapters and Mechanical Interfaces

The integration of Altec compression drivers with various horn models required specialized throat adapters. These components served as the mechanical and acoustic bridge between the driver's exit and the horn's entry. Because Altec drivers were produced in different formats—primarily 1-inch and 1.4-inch throat diameters—the selection of the correct adapter was critical.[11]

Table 2: Altec Throat Adapters and Compatibility

Part Number	Description/Function	Primary Horn Compatibility	Driver Format
30162	Single-driver adapter	803B, 805B	1.4" (288/290/291)
30166	Single-driver adapter	1505B	1.4" (288/290/291)
30170	Dual-driver adapter	1003B, 1005B	(2) 1.4" Drivers
30172	Dual-driver adapter	1505B	(2) 1.4" Drivers
30210	Single-driver adapter	1003B, 1005B	1.4" (288/290/291)
21216	1.4" to 2" transition	311-60, 311-90	1.4" Drivers
33710	Multi-format adapter	Universal/Specific applications	1.4" to 1" or vice-versa
30546	Weatherproof 45° adapter	Sectoral/Multicellular	1.4" Drivers
30619	Curved throat section	Specific Multicellular	1.4" Drivers

The 30170 and 30172 adapters were specifically engineered to allow two large-format compression drivers to be mounted to a single horn. This doubled the power handling and increased the maximum sound pressure level by approximately 3 dB, which was essential for the massive A-2 systems used in large premiere houses.[3]

Installation manuals emphasized the importance of proper gasketing to prevent air leaks, which would manifest as acoustic cancellations and reduced efficiency. Specifically, if an adapter or throat featured a 1/8 inch raised step, a #1 gasket was used; if the face was flat, a #3 gasket was required.[14]Compression Driver Evolution and Performance

To understand the utility of the horns, one must examine the drivers that powered them. Altec compression drivers were noted for their use of high-grade magnetic materials and sophisticated phasing plugs.The Alnico V Revolution

Early Altec drivers utilized field coils, but the introduction of Alnico V permanent magnets during WWII allowed for more compact and efficient designs.[4] Alnico V, an alloy of aluminum, nickel, cobalt, and iron, provided a higher magnetic flux density than traditional magnets, enabling the high sensitivity (often exceeding 110 dB at 1 watt/1 meter) for which Altec was famous.[4]

Table 3: Key Altec Compression Driver Specifications

Driver Model	Throat Size	Impedance	Diaphragm Material	Recommended Crossover	Application
802-8G	1"	$8\Omega$	Aluminum	500 Hz	Hi-Fi / Studio
806A	1"	$16\Omega$	Aluminum	$800\text{ Hz}$	VOTT A-7/A-8
808-8B	1"	$8\Omega$	Symbiotik	$500\text{ Hz}$	Sound Reinforcement
288-16G	1.4"	$16\Omega$	Aluminum	$300\text{ Hz}$ 300 Hz / 500 Hz $500\text{ Hz}$	Cinema / Large Pro
291-16B	1.4"	$16\Omega$	Symbiotik	$500\text{ Hz}$	Touring Sound
290-8G	1.4"	$8\Omega$	Phenolic	$300\text{ Hz}$	Public Address / Speech
902-8A	1"	$8\Omega$	Aluminum	$1200\text{ Hz}$	Model 14 / Studio

The 288 series was the flagship large-format driver, often paired with the 1505B horn.[3] In the late 1970s, Altec introduced the "Tangerine" radial phasing plug, which replaced the older circumferential slit design.[4] This innovation improved the high-frequency extension by ensuring a more uniform pressure distribution across the throat, allowing drivers to reach beyond 18 kHz with less distortion.[4]Diaphragm Varieties: Aluminum vs. Symbiotik

Altec offered two primary diaphragm materials to suit different applications. Aluminum diaphragms provided the most extended high-frequency response and were the standard for studio monitoring and high-fidelity use.[2] However, aluminum is fragile and susceptible to damage from high-power transients.

To address the needs of the emerging touring sound market, Altec developed "Symbiotik" diaphragms. These featured an aluminum dome with a reinforced suspension made of a more flexible material.[12] While Symbiotik diaphragms had a slightly truncated high-frequency response compared to pure aluminum versions, they were significantly more durable and could withstand the rigors of high-level sound reinforcement.[12]The Duplex Concept: Integrating Horn and Woofer

In 1941, Altec pioneered the Duplex loudspeaker, which combined a high-frequency horn and a low-frequency driver into a single coaxial unit.[4] The goal was to create a point-source radiator that eliminated the phase and timing issues associated with physically separated drivers.

The 604 series is the most celebrated iteration of the Duplex design. Early models (A and B) used a 2x3 multicellular horn mounted in front of the woofer cone.[4] The backside of this horn was coated with a damping compound to prevent reflections off the woofer.[4] Starting with the 604C, the high-frequency section transitioned to a sectoral horn with vanes.[4]

Table 4: Altec 604 Series Evolution

Model	Magnet Type	HF Horn Type	Crossover Frequency	Notes
604	Alnico V	Multicell (2x3)	$2000\text{ Hz}$	First permanent magnet version
604B	Alnico V	Multicell (2x3)	$1000\text{ Hz}$	Improved power handling
604C	Alnico V	Sectoral w/ Vanes	$1600\text{ Hz}$	Major redesign of HF section
604E	Alnico V	Sectoral w/ Vanes	$1500\text{ Hz}$	Widely used in studios
604-8G	Alnico V	Sectoral w/ Vanes	$1500\text{ Hz}$	High power version
604-8K	Ferrite	Mantaray	$1500\text{ Hz}$	Tangerine plug and Mantaray horn

The transition from Alnico to Ferrite magnets in the "K" series was necessitated by the rising cost and scarcity of cobalt.[4] While Ferrite magnets are larger and heavier, Altec engineers utilized the new Mantaray horn and Tangerine phasing plug to ensure the 604-8K remained competitive in performance.[4]Mounting Hardware and Structural Support

The sheer weight and size of Altec horn-driver combinations necessitated specialized mounting brackets. These brackets served two purposes: supporting the mechanical load and allowing for the alignment of the horn's acoustic axis.Sectoral Horn Brackets

For the 511B and 811B horns, which were typically mounted atop the "Voice of the Theatre" cabinets, Altec produced throat support brackets.[15] These steel brackets bolted to the horn's throat and rested on the top of the cabinet, ensuring that the heavy compression driver did not put excessive cantilevered stress on the horn's cast aluminum mouth.[21]Heavy Duty and Universal Mounting

In professional installations—such as stadiums, convention halls, and airports—Altec required hardware that could withstand environmental stresses and facilitate complex arrays.

Universal Mount Brackets: Often made of stainless steel or galvanized iron, these were used to secure large arrays to walls or ceilings.[22]
Pole Mount Kits: In paging and outdoor sound reinforcement, Altec horns were often mounted to poles using heavy-duty galvanized steel brackets and adjustable stainless steel bands.[23]
Weldment Brackets: In mobile or industrial applications, heavy-duty weldment brackets were used to provide a rigid connection for massive horns in high-vibration environments.[25]

Directivity Analysis: Latitude and Longitude Measurements

A defining characteristic of Altec's engineering was the rigorous measurement of polar response. Technical Letter No. 255 details the methodology for measuring the "sphere of radiation" around a horn.[9] By rotating the horn around its horizontal apex and measuring the sound pressure level at various latitudes and longitudes, Altec engineers produced "Nested Angular Contours."[9]

These contours, typically showing -6 dB, -10 dB, and -15 dB levels, allowed sound contractors to predict the coverage evenness in an auditorium.[9] Sectoral horns, while uniform in their rated coverage angles, tended to narrow their dispersion at very high frequencies (a phenomenon known as "beaming"). The Mantaray series, introduced in the late 1970s, addressed this by providing constant directivity, ensuring the coverage pattern remained stable across the entire frequency range.[4]Implications of Coverage for Venue Design

In a typical auditorium, the goal is to provide a direct-to-reverberant sound ratio that ensures high speech intelligibility. A horn with wide horizontal dispersion (like the 1005B at 50°) is ideal for broad seating areas, whereas a narrow-dispersion horn (like the 203B at 40°) is better suited for long-throw applications where sound must be projected to the rear of a hall without bouncing off the side walls.[9]Damping and Acoustic Treatment: The Role of Aquaplas

One of the criticisms of early metal horns was their tendency to "ring" like a bell when excited by certain frequencies. To mitigate this, Altec developed "Aquaplas," a proprietary damping compound.[6] Aquaplas was applied to the exterior of cast aluminum sectoral horns and the interiors of certain multicellular cells.

The compound acted as a viscoelastic damper, converting mechanical vibrational energy into heat. This treatment was essential for achieving the "firm, thick sound" for which the 311 series was noted.[7] Without damping, the metallic resonance of the horn would color the sound, leading to listener fatigue and a loss of clarity in the upper midrange.The Modern Legacy and Restoration of Vintage Altec Components

The enduring popularity of vintage Altec gear has created a robust secondary market. Audiophiles prize the "naturalness" and "effortless dynamics" of these large horn systems, which are difficult to replicate with modern small-format speakers.Market Valuation and Availability

Restored Altec components command significant prices. A pair of 311-60 horns might sell for nearly $2,000, while rare multicellular horns like the 1505B can reach several thousand dollars.[7] The availability of original-specification replacement parts is critical for maintaining these systems. Great Plains Acoustics, founded by former Altec employees, remains the primary source for authentic diaphragms, recone kits, and even new production runs of classic drivers like the 515 and 288.[16]Technical Challenges in Restoration

Restoring a vintage Altec horn involves more than just a fresh coat of paint. The primary technical challenges include:

Magnet Recharging: Over decades, Alnico V magnets can lose some of their flux density, especially if they have been subjected to physical shocks or placed near other strong magnets. Professional restorers use massive capacitor-discharge magnetizers to return the magnets to their original factory specifications.[4]
Gap Cleaning: The magnetic gap of a compression driver is incredibly tight. Any debris—iron filings, dust, or oxidized plating—will cause the voice coil to rub, leading to distortion or failure.
Diaphragm Alignment: Aligning a replacement diaphragm requires precision. Even a slight misalignment will result in uneven frequency response. Many Altec drivers utilize dowel pins for alignment, but fine-tuning is often done by monitoring a sine wave sweep on an oscilloscope while tightening the mounting screws.[14]

Conclusion: The Enduring Impact of Altec Lansing

The vintage Altec horns and brackets described in this report represent the pinnacle of mid-century acoustic engineering. By prioritizing efficiency, directivity, and mechanical integrity, Altec Lansing created a body of work that defined the sound of cinema and professional audio for fifty years.[1] The multicellular horns remain a testament to the pursuit of perfect dispersion, while the sectoral horns and Duplex drivers brought studio-grade monitoring into the reach of professionals and enthusiasts alike.[2]

The technical specifications—from the 300 Hz cutoff of the 203B to the sophisticated radial phasing of the Tangerine plug—reveal a company that was never content with the status quo.[4] For the modern audio engineer or collector, these components are not merely historical artifacts; they are high-performance tools that continue to offer a level of musical engagement that is as relevant today as it was when the first "Voice of the Theatre" system was unveiled. The structural supports and throat adapters, though often overlooked, were the essential hardware that allowed these acoustic giants to be integrated into the complex soundscapes of the twentieth century, ensuring that the "All Technical" promise of the Altec name was fulfilled in every installation.[1]Works cited

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