Western Electric 639A (1938)

That deep, chesty growl you hear on old radio dramas and live recordings? There’s a good chance it’s coming from this hulking, caged beast of a mic.

Overview

The Western Electric 639A “Bird-cage” microphone isn’t just a relic—it’s a statement. From the moment you lay eyes on it, you know it means business. Introduced in 1938, this dual-element microphone combined both a dynamic moving-coil capsule and a ribbon velocity transducer in a single, imposing shell, giving engineers unprecedented flexibility in a time when most mics did one thing and did it only one way. It was Western Electric’s bold answer to the dominance of RCA’s DX77 and BX44 series, designed to offer multi-pattern capabilities without stepping on patent toes. And it worked—so well, in fact, that it became a staple in broadcast studios, government chambers, and even international assemblies like the United Nations.

What sets the 639A apart isn’t just its sound—it’s the architecture. Unlike modern multi-pattern mics that rely on back-to-back diaphragms or complex acoustic labyrinths, the 639A used two completely different transduction methods: a dynamic element (omnidirectional by nature) and a ribbon element (inherently bidirectional). By combining these via a selector switch at the base, it could produce cardioid, bidirectional, and omnidirectional patterns—three in total—labeled on the switch as C (Combined), D (Dynamic only), and R (Ribbon only). That kind of versatility in 1938 was nothing short of revolutionary.

And let’s talk about that look: five-and-a-half inches high, about six inches around, with a prominent wire cage that gives it the nickname “Bird-cage.” Under that cage, owners report the original silk lining often remains intact, a whisper of mid-century manufacturing detail that’s as functional as it is nostalgic. It’s heavy—“a weight to match the size,” as one source put it—and it feels like it was built to last through wars, regime changes, and at least four generations of audio engineers. Which, frankly, it did. Units were still in active use in the Denver area as late as the 1980s, and Dave Felice tracked with one through a WE 23A console from 1969 to 1971. That’s staying power.

But make no mistake—this isn’t a mic for the faint of heart or the electrically careless. It’s passive, yes, but it’s also fragile in ways that matter. The dynamic capsule, about 34mm in diameter with a depth of roughly 20mm, uses thin wires that are notorious for breaking or losing connection over time. And the internal components—a transformer, inductor, 620-ohm resistor, and 0.12 microfarad capacitor—are sealed in goop after assembly, making repairs a delicate operation. One wrong move and you’re not just out a few hundred bucks—you’re out a piece of broadcast history.

Specifications

Key Features

Dual-Element Design: Two Mics in One

The 639A doesn’t just switch polar patterns—it switches transducers. Flip the switch to “D” and you’re using the dynamic moving-coil element, which is inherently omnidirectional and delivers a tighter, more focused upper midrange with noticeably less low end. Switch to “R” and you’re in ribbon territory: full, warm, with a ton of low-end presence and good sensitivity, as owners describe it. But the magic happens at “C,” where both elements combine to create a cardioid pattern. This isn’t electronic trickery—it’s acoustic summation. The dynamic’s omni response and the ribbon’s figure-eight are blended via the internal circuit to produce a directional pickup that rejects sound from the rear, making it ideal for live broadcasts and studio isolation long before close-miking became standard.

Internal Circuitry: Passive but Purposeful

Inside that hefty shell lives a carefully balanced network: a transformer for impedance matching and amplification of the ribbon’s low output, an inductor, a 620-ohm resistor, and a 0.12 microfarad capacitor. These components aren’t just there to take up space—they shape the interaction between the two elements and ensure the combined output remains stable across patterns. The transformer, in particular, is critical: it boosts the ribbon signal to usable levels while maintaining the 30 to 50 ohm output impedance, making it compatible with the tube consoles of its era. Four wires from the transformer come up through the sealed base of the dynamic chamber, soldered and then locked in place with goop—a construction method that prevented moisture ingress but makes servicing a real adventure.

Build and Usability

The 639A was built for broadcast desks, not studio stands. Its base-mounted pattern selector switch is large and tactile—engineers could change patterns without looking, a necessity during live radio plays or political hearings. The wire cage isn’t just for show; it acts as a windscreen and protects the delicate internal elements from plosives and physical damage. Under the cage, the silk lining—still found in many surviving units—helps dampen internal reflections and adds a subtle high-frequency roll-off that contributes to its “classic” tone. And while it lacks the sleekness of later Altec designs, its industrial heft commands attention. This was a tool for professionals, not a fashion accessory.

Historical Context

Western Electric introduced the 639A in 1938 with a clear mission: break RCA’s grip on the high-end broadcast microphone market. The RCA DX77 and BX44 series were dominant, but their designs were protected by patents. Western Electric, working through Bell Labs, engineered a workaround—one that used a hybrid dynamic/ribbon approach rather than RCA’s single-element capsule designs. The result was a patentable innovation: William Harry and Robert Marshall of Bell Labs secured a design patent for the 639 in early 1941. The mic didn’t just compete—it thrived. It was adopted widely, from congressional hearings to United Nations assemblies, and remained in service for decades.

In October 1949, as part of a federal anti-monopoly order, Western Electric spun off its audio division to form Altec. The 639 design lived on, now branded as the Altec 639—identical in every way to the Western Electric version. The 639B followed, expanding the choice of patterns, but the 639A remained the original and most iconic. Its legacy is not just in its sound, but in its role as a bridge between eras: a pre-war design that outlasted the companies that made it.

Collectibility & Value

The Western Electric 639A is still in high demand, with serviced units sometimes selling for thousands of dollars. It’s frequently described as “rare vintage” and “classic sounding,” with a reputation that’s only grown over time. However, owning one isn’t just about bragging rights—it’s a commitment. The thin wires in the dynamic capsule are a known failure point, often breaking or losing connection with age or vibration. The pattern selector switch, while robust, can suffer from contact oxidation and may need cleaning or tensioning to function reliably. And while a new ribbon installation is common during servicing, it’s not a DIY job for the uninitiated.

One warning stands above all: do not apply phantom power. The 639A is entirely passive and contains no active electronics, but the delicate ribbon and transformer are not designed to handle 48 volts. Doing so could destroy the microphone instantly. Collectors and users alike treat these with reverence—not just because of their price, but because of their irreplaceable role in audio history. Even the parts donors are valuable: the Altec 633 “Saltshaker” mic, sometimes used for repairs, was selling for $400+ as of May 2021.

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