Western Electric 597A (1929–?)

A thin aluminum ribbon sits inside a die-cast frame. It was built to fix what the big horns got wrong.

Overview

The Western Electric 597A is a field coil compression driver with an attached horn. Specifically, it is a high-frequency correction unit, and it came out of frustration. In 1929, Western Electric engineers saw a problem with their 15A, 16A, and 22A horns. Powerful as they were, their response fell off sharply around 3-4kHz at 6dB per octave. Mids and highs lost energy fast, and that led to complaints, bad press, and a reputation for dullness in real-world listening. The 597A was engineered to correct that. It is a precision tweeter added to restore clarity where the system was losing it.

The full name is the Western Electric 597A Field Tweeter. It is also referred to as the WE-597A or the Bostwick Tweeter. It is a field coil driver, so it needs an external power supply to energize its magnetic field, like the big WE low-frequency drivers of the era. That makes it a project. You have to wire up the extra supply and design the right crossover. The payoff is reportedly transformative. Paired with a WE-555 driver, or integrated into ALTEC or Jensen systems, owners note a distinct "WE unique luster" and a "very soft texture" in the highs. The sound is described as clear, transparent, and beautiful, for a component designed nearly a century ago to solve an engineering flaw.

What’s striking isn’t just the performance, but the build. The voice coil uses an edgewise-wound aluminum ribbon, made from wire so fine it’s “about the same thickness as a hair”—even finer than that used in the WE-594A. That ribbon is wound on an ultra-thin bobbin and mounted rigidly in a die-cast aluminum frame with zero play. There’s no slop, no wiggle—just absolute mechanical integrity. It’s the kind of construction that makes you question whether anything made after 1950 has any right calling itself well-built. The patents stamped on its label—1707544, 1707545, 1730425, 1734624, and 1907723—aren’t just decoration. They’re a paper trail of innovation, each representing a small battle won in the war for fidelity.

Specifications

Manufacturer	Western Electric Co., Inc.
Product type	high frequency compression driver with attached horn, field coil driver
Voice coil impedance	20.6 ohms
Field coil impedance	7.1 ohms
Field coil power supply requirement	6-7 volts at one amp
Serial number (example)	1480

Key Features

Edgewise-Wound Aluminum Ribbon Voice Coil

The voice coil is the heart of the 597A. It is an aluminum ribbon wound edgewise, meaning the flat side of the wire faces outward to maximize surface area in the magnetic gap. The wire is thinner than that used in the WE-594A, reportedly "about the same thickness as a hair." That cuts mass dramatically, so the diaphragm can respond with great speed and detail. Owners describe the transparency as "very clear" and "beautiful." The trade-off is fragility. The delicate ribbon needs proper crossover protection and stable operating conditions. Abuse it and it won't survive.

Die-Cast Aluminum Frame and Rigid Mounting

Western Electric didn’t skimp on structure. The voice coil assembly is mounted in a “very sturdy die-cast aluminum frame” with no looseness—every part locked down, every vibration damped. This isn’t overbuilt; it’s precision-built. Any flex or resonance in the frame would smear the transient response, but the 597A’s construction eliminates that risk. The frame isn’t just a housing—it’s part of the acoustic design, ensuring the magnetic gap stays perfectly aligned and the diaphragm moves only as intended. It’s one reason the unit still commands awe nearly a century later: the build quality is so far beyond its time that it feels almost alien today.

Field Coil Excitation

Like the best WE drivers of its era, the 597A uses a field coil instead of a permanent magnet. It requires an external 6-7 volt DC power supply delivering one amp to energize the magnetic field. By modern standards that means another box, more wiring, and another point of failure. Field coils produce a stronger, more stable magnetic field than early permanent magnets, which leads to lower distortion, better damping, and a more dynamic presentation. This is why owners report that "WE unique luster," a shimmer and ease in the highs. You need to research the correct crossover frequency and make sure the power supply is clean and stable.

Integrated Horn and Patent Portfolio

The 597A is a driver with an attached horn, which makes it a complete high-frequency compression unit. The horn shape and flare are tuned to the driver's output for smooth dispersion and efficient coupling to the air. It is not user-replaceable or modular. It is a matched system, engineered as a whole. The five patents on its label - 1707544, 1707545, 1730425, 1734624, and 1907723 - cover voice coil construction, magnetic circuit design, and horn coupling.

Historical Context

The Western Electric 597A BOSTWICK TWEETER was developed starting in 1929 as a high-range correction unit for the 555W receiver. It was a necessary fix, not a luxury add-on or a high-end upgrade. The 15A, 16A, and 22A horns were powerful and widely used in theater and broadcast systems, but they had a narrow frequency band. Energy dropped off steeply around 3-4kHz at a rate of 6dB per octave, so music sounded dull and speech lacked presence. Complaints piled up and reviews turned negative. Western Electric responded with engineering, not marketing. The 597A was a targeted high-frequency supplement to restore balance. It wasn't meant to stand alone.

Collectibility & Value

The original WE-597A is considered particularly hard to obtain, even by Western Electric standards. Collectors report that almost no WE-597A units are circulating on the used market right now. One auction listing confirms at least one unit (serial number 1480), but no sale price was disclosed, so current market value is unknown. Given its scarcity and the complexity of field coil operation, ownership is limited to specialists and restoration experts. Before buying one, measure both voice coil and field coil continuity and impedance to verify it works. Common problems include loss of voice coil and field coil continuity and incorrect impedance. Restoration requires a dedicated power supply for the field coil and a properly designed crossover. Research into historical literature is recommended to determine the correct crossover frequency.