Altec Lansing 605A Duplex

At 110 dB sensitivity, it doesn’t just play loud—it commands the room.

Overview

The Altec Lansing 605A Duplex isn’t the star of the studio monitor pantheon like its older sibling, but it’s the one that got the job done when budgets were tight and deadlines loomed. This coaxial loudspeaker/driver emerged during a period when American sound reinforcement was shifting from raw power to more refined control, and the 605A landed squarely in that transition. While some sources cite a production start as early as 1954, others point to 1959 or even reference a 1951 advertisement—suggesting either a long production run or early prototypes bearing the name. A specific unit dated 1963 confirms the model was still in circulation at mid-century, but no definitive end year is documented.

Born as a slightly upgraded version of its predecessor, the 605A was positioned as a more affordable alternative to the legendary 604 Duplex. At $175, it undercut the $177 604D by a razor-thin margin—more symbolic than substantial. Still, that pricing, combined with its coaxial design, made it a practical choice for regional studios, broadcast booths, and theater installations across the US, where it became a common fixture. It wasn’t marketed as a hi-fi curiosity; it was working gear, built to endure daily use in professional environments.

Despite its utilitarian roots, the 605A carries a certain mystique. One unit surfaced with a claim to Abbey Road/Beatles provenance, instantly elevating its collectible status, though such claims remain unverified. Sonically, opinions are split but rarely dismissive. Some forum veterans note it “did not meet with rave reviews” compared to the 604, while others insist “you can build a good system with 604 or 605”. User reviews echo this balance—a 4.5 out of 5 stars here, a simple “They sound great” there. It’s not revered, but it’s respected.

Specifications

Key Features

Coaxial "Duplex" Design with Rear-Mounted Tweeter

The 605A follows Altec’s signature coaxial "Duplex" architecture, where the high-frequency driver is mounted directly behind the woofer cone. This alignment ensures that both low and high frequencies originate from a single point source, improving off-axis coherence and reducing phase anomalies—critical for studio monitoring where consistent response matters more than sheer tonal warmth. The physical offset between the woofer and tweeter diaphragms is 4.25 inches, a design compromise inherent to the era’s engineering, which the later 605A/B Phase Corrected Crossover attempts to mitigate.

416 Woofer with 806 High-Frequency Driver Mating

At its core, the 605A is a marriage of two proven Altec components: the 416 woofer and the 806 high-frequency driver. The 416 woofer, driven by the 416 magnet structure, provides the muscle, while the 806 HF driver—utilizing either the 804 or 806 magnet—handles the upper register with the efficiency Altec was known for. This modular approach allowed for easier servicing and alignment in the field, a necessity in the pre-solid-state era when tubes and voice coils failed with regularity.

Smaller Magnets and Higher Qt for Improved Low-Frequency Coupling

Compared to the 604, the 605A uses smaller magnets, which results in a higher Qt (total system Q). While this reduces overall efficiency slightly—evident in the 110 dB sensitivity versus the 604’s greater efficiency—it improves low-frequency output in certain enclosures. Owners report that the higher Qt makes the 605A better suited to home-style cabinets, where extended bass response is often a priority. The smaller magnets also reduce the time delay between LF and HF drivers, a subtle but meaningful improvement in transient alignment.

Historical Context

Positioned as the "poor little brother to the 604", the 605A inherited the DNA of a legend but with cost-cutting measures that defined its identity. The analogy drawn by collectors holds: where the 604 used the 515 magnet and 802 HF magnet, the 605A stepped down to the 416 and 804/806 equivalents. This wasn’t a downgrade in function so much as a recalibration for a different market. It wasn’t meant to dethrone the 604—it was meant to extend Altec’s reach into studios and installations that couldn’t justify the premium. The result was a driver that didn’t dazzle in spec sheets but delivered reliable, punchy performance where it counted.

Collectibility & Value

Market data remains sparse, but available listings suggest a quiet but steady demand. A pair of 605A coaxial drivers was listed on eBay, while UK Audio Mart shows a pair with an asking price of $1500.00. A single 1963 unit with crossover appeared on Reverb with a “New Price” tag of $475, though whether that reflects actual sales is unclear. The Abbey Road-provenance claim adds a speculative premium, but without documentation, it’s more folklore than valuation driver. No data exists on common failures or maintenance, though given the era, reconing and crossover capacitor replacement are likely necessary for unrestored units.

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