Altec 804A

At 19 pounds, it's heavier than most guitar amps half its size, and it's built from cast metal and aluminum. It still sounds clear decades later.

Overview

The Altec 804A is a high-frequency compression driver made by Altec Lansing. It sits in the shadow of its better-known sibling, the 802D, but it's a classic model in its own right. It was designed for smaller spaces like home listening rooms or modest recording studios, meaning non-reverberant conditions with moderate ambient noise. Those are the spaces where most people actually listened to music. It's not a stadium-filling driver. It's meant to deliver clean, articulate highs without overwhelming the room.

What surprises many first encountering the 804A is how much engineering is packed into a unit that, on paper, shares DNA with others in the Altec lineup. It uses a 1.75" aluminum ribbon edge-wound voice coil coupled to a 2.25" aluminum diaphragm with tangential compliance—a design choice that enhances linearity and reduces distortion at high frequencies. A mechanical phasing plug with two exponential acoustic slots ensures that sound waves from the center and outer edges of the diaphragm arrive in phase, a critical detail for coherent dispersion and time alignment. This isn’t guesswork; it’s deliberate acoustic architecture. The result is a driver capable of reaching up to 22,000 Hz, though real-world listening reports suggest a slight softening above 10 kHz, particularly when paired with certain crossovers like the N-800-F.

The 804A looks like the 806A, but it isn't identical. Internally it diverges significantly, though the available documentation doesn't fully detail how. It shares core design principles with the 802D, with one key difference: the magnet. The 802D has a 1.2 lb., 15,250 Gauss magnet. The 804A uses a 13 oz., 13,000 Gauss unit. That lower magnetic strength affects efficiency and output capability, so the 804A is the more modest performer, better suited to lower-SPL environments. Still, in listening comparisons at moderate levels (around 80-95 dB SPL), the sonic differences between the two are reportedly minimal.

In full-system applications, such as the "Stokowski" speakers built with Duelund CAST crossovers, the 804A is praised for a musically natural, intensely beautiful presentation, a stunning midrange and overall coherence. The same setups show its limits. The top end is described as slightly soft, and the bass is powerful but doesn't reach deep. That's part of the Altec "sound," which enthusiasts either chase or correct with careful system matching.

Specifications

Manufacturer	Altec Lansing
Product type	High-frequency compression driver
Magnet weight	13 oz
Magnet strength	13,000 Gauss
Impedance	16 ohms
Power rating	30W
Frequency response	500Hz to 22,000Hz
Voice coil diameter	1.75"
Driver diameter	4.5"
Pressure sensitivity	109.5dB at 1W and 124.2dB at 30W
Crossover frequency (in typical application)	800 Hz
Gap flux	approximately 12,000 gauss
Cone resonance	25 cycles
Dimensions	15 1/2" diameter, 7" deep
Weight	19 lbs

Key Features

1.75" Aluminum Ribbon Edge-Wound Voice Coil with Tangential Compliance

The 804A has a 1.75" aluminum ribbon edge-wound voice coil. It improves heat dissipation and reduces mass compared to traditional round-wire coils. It's paired with a 2.25" aluminum diaphragm featuring tangential compliance, which allows greater linearity in high-frequency reproduction. The compliance design helps decouple mechanical stresses, reducing distortion and smoothing response across the driver's operating range.

Mechanical Phasing Plug with Exponential Acoustic Slots

The phasing plug sits at the heart of the driver and incorporates two exponential acoustic slots. These slots manage the phase relationship between sound waves generated at the center and outer edges of the diaphragm, so the output stays time-coherent. That keeps clarity and directivity up, especially when the driver is coupled to a horn.

13 oz., 13,000 Gauss Magnet Assembly

The 804A has a 13 oz. magnet producing 13,000 Gauss, a step down from the 802D's 1.2 lb., 15,250 Gauss unit. That puts it lower in the lineup: less output and lower efficiency, but still enough for domestic and studio monitoring. The gap flux is reportedly around 12,000 gauss, indicating strong magnetic coupling in the voice coil gap.

Internal Design Differences from 806A

The 804A and 806A look identical from the outside, but they are not the same driver. Documentation confirms internal differences, though it doesn't give specifics. For restoration and replacement, owners can't assume the two are interchangeable based on appearance alone.

Shared Core Design with 802D

The 804A and 802D are fundamentally the same compression driver design, differing primarily in magnet size and strength. That shared architecture explains why listening tests reveal minimal sonic differences at moderate levels. The 804A can be seen as a cost- or application-optimized variant of the 802D, tailored for environments where extreme output isn't required.

Historical Context

The Altec 804A was engineered for non-reverberant spaces with moderate ambient noise, typical of average home listening rooms or smaller broadcast and recording studios. It wasn't intended for large venues or high-noise environments. It was meant for critical listening where clarity and accuracy mattered more than raw volume.

Collectibility & Value

The 802D enjoys legendary status, while the 804A gets discussed less, despite being a classic model in Altec's own classification. A used unit was once listed for $249 in "Near New Cond," and current market listings show similar drivers, sometimes mounted in horns like the H-811 B, priced around $325.00. It's sought after by DIY speaker builders and vintage audio enthusiasts for its performance, retro charm and build quality. No data exists on original pricing, production years, or common failure modes.