Altec 811B Horn
A cast aluminum sectoral horn that rings like a bell when it isn't bolted down - and sounds like nothing else when it is.
Overview
Pick up an Altec 811B and you notice right away that it's a casting, not a stamping. It's a solid piece of aluminum with an exponential flare that measures 476mm wide by 219mm high by 343mm deep. Altec Lansing built it in the United States as a sectoral horn, sometimes called a "Mantarraya" horn in period literature. Its job was to couple a high-frequency compression driver to the air with a rated 90° x 40° coverage pattern. That wide, shallow window is the classic cinema and sound-reinforcement shape. It spreads the sound across a room without wasting energy on the ceiling.
The 811B is a component, not a speaker. It has no cabinet, no crossover, no driver of its own. You bolt a compression driver to its 1-inch throat and hand it everything above roughly 800 cycles, the horn's stated lower reinforcement limit. The company's own driver literature from the era pairs it with the 802, 806, 807, 808, and 902 series compression drivers. In the Valencia consumer speaker it ran with the 806 driver. In the 820C Corner Speaker System it served as the high-frequency section. That is why the 811B turns up in so many different systems, and why collectors still chase clean examples for horn builds.
What it sounds like depends almost entirely on what you bolt to it and how you mount it. The horn itself is a passive flare, and the driver does the transducing. But the flare shapes everything, and the 811B's exponential expansion gives it the controlled dispersion that made Altec's sectoral horns famous. It is also, by all accounts, a piece of metal that will ring audibly if you don't mount it properly. That's not a defect. It's a physical property of a thin cast aluminum horn.
Key Features
Cast Aluminum Exponential Flare
The 811B is cast aluminum, and the flare follows an exponential expansion profile. That geometry lets a horn load a driver smoothly across its passband while controlling where the sound goes. The rated coverage is 90° horizontal by 40° vertical. That is wide enough to cover a seated audience across a room and tight enough vertically to keep energy off the floor and ceiling. It's the same broad approach as Altec's multicell theater horns, done here in a simpler sectoral form. The casting is rigid and heavy enough to hold its shape, and a horn that flexes loses control of its pattern.
Designed for Altec Compression Drivers
Altec built the 811B to work with its own high-frequency compression drivers. The 802, 806, 807, 808, and 902 series are all listed as compatible. The throat accepts a 1-inch driver mount, and the pairing determines everything about the resulting sound. In the Valencia, it ran with the 806. Period documentation for the 808-8A driver cites a frequency response of 800 to 20,000 Hz when that driver is mounted on the 811B with the N801-8A dividing network. That figure belongs to the driver, horn and crossover together, not the bare horn. Crossover is typically set at 500 Hz or higher, depending on the driver and the bass section it's paired with.
The Ringing Problem — and Aquaplas
Here's the honest part. The 811B is known to resonate audibly if it isn't securely mounted to a proper bass enclosure. Owners describe it as ringing "like a bell." A cast aluminum horn is a resonant structure, and bolting it to a flimsy baffle or hanging it free lets that resonance color everything the driver produces. The fix is mechanical. Mount it solidly, and if that isn't enough, damp it. Users have wrapped the exterior to reduce vibration, and modifiers have gone further, lining the surfaces with constrained-layer damping material. Altec itself eventually addressed the issue at the factory. Very late production runs of the 811 and 511, built just before the company folded at its Anaheim, California factory, were coated with Aquaplas to damp the resonance. Earlier examples have no such treatment, which is one reason late-run horns carry a quiet premium.
Roughly 800 Cycles and Up
Altec rated the 811B's lower reinforcement limit at 800 cycles. Below that point the horn stops contributing meaningful acoustic gain, so the 811B is a high-frequency device, not a midrange workhorse. Cross it at 500 Hz or above and let a proper bass driver handle everything underneath. The upside is efficiency. A horn this size loading a sensitive compression driver will produce serious output from very little power. System power handling is quoted at 20-50W RMS depending on the driver, so the driver, not the horn, is the limiting factor.
Historical Context
Altec's sectoral horns were a fixture of the company's component catalog through the 1950s and 1960s. A 1955 High-Fidelity advertisement paired the 802C driver with the H-811B horn and claimed a guaranteed range to 22,000 cycles (High-Fidelity, July 1955, p.27). The original 811 dates to 1952 as a one-piece casting with mouth fins. The 811B is a later variant, and specific construction details for the B version aren't fully documented in the surviving record. What is documented is how it was used: as the high-frequency section of the 820C Corner Speaker System, and paired with the 806 compression driver in the Valencia consumer speaker. Period Altec combinations pairing the 806-8A driver with 811B horns are dated 1973-1976 and marked made in USA, though that date applies to the combination, not to the horn alone. A 1964 catalog listing for the 811B describes it as similar to the larger 511B but with an 800-cycle cutoff, sold alongside Altec's sectoral horn line (HiFI-Stereo, 1964, p.108). Production ran at least into the Anaheim era, ending when Altec ceased operations there.
Owners comparing the 811B to the 511B often note that one of the two can supposedly be crossed over lower, though the sources don't settle which. The 811B's own 800-cycle limit suggests it's the smaller of the pair. The 811B became a favorite in vintage horn builds, particularly among people recreating classic Altec systems like the Model 19, and it remains one of the more accessible entry points into Altec horn sound.
Collectibility & Value
Vintage Altec drivers and speakers are highly prized by collectors, and the 811B is no exception. The horn has been listed for sale at $275 for a pair, though no date is attached to that figure. Current listings show a wide spread, complicated by the fact that many sellers bundle a driver with the horn. A pair of powdercoated 811B horns has been offered at $400, a 1959 802D driver with an H-811B horn at $550, an H-811B with an 807-8A driver at $300, and an 811B with a 902-8B driver at $330. One reseller lists the 811B horn-driver combination across a range from $160 to $1,600. Bare horns sell for less than driver-and-horn pairs, and matching pairs command more than singles.
The resonance issue is manageable and well understood. A horn that rings in free air will settle down once it's bolted to a solid baffle. Late Anaheim-production examples with factory Aquaplas coating are worth seeking out for that reason. Beyond the ringing, no common failure modes or parts-availability warnings turn up in the record. These are simple castings that mostly need a solid mount and a good driver.
eBay Listings
As an eBay Partner, we earn from qualifying purchases. This helps support our independent vintage technology research.