ESS TEMPEST-SERIES: The Forgotten Flagship of Planar Innovation

In the golden era of high-end audio during the 1980s, few names stirred as much curiosity and reverence among audiophiles as ESS (Electro-Static Sound). Best known for their groundbreaking planar magnetic loudspeakers, ESS pushed the boundaries of transducer design with a relentless pursuit of sonic purity. Among their most ambitious and elusive creations was the TEMPEST-SERIES—a rare, limited-production line of hybrid planar speakers that represented the pinnacle of the company’s engineering philosophy during its peak years.

Though not as widely documented as ESS’s more famous models like the CA-1 or Model Eight, the TEMPEST-SERIES holds a cult status among vintage audio connoisseurs. It was conceived not merely as a speaker, but as a complete acoustic statement—an attempt to merge the speed and transparency of planar magnetics with the dynamic authority of conventional cone drivers. The result was a speaker that, while challenging to drive and rare to encounter, delivered a listening experience that many who heard it still describe as “revelatory.”

Historical Context: ESS in the 1980s

Founded in the late 1970s by a group of audio engineers with backgrounds in aerospace and acoustics, ESS quickly distinguished itself by adopting planar magnetic technology at a time when electrostatics and dynamic drivers dominated the high-end market. Their breakthrough came with the Model Four, a full-range quasi-ribbon driver that offered extraordinary transient response and low distortion.

By the mid-1980s, ESS was experimenting with larger, more ambitious designs, culminating in the TEMPEST-SERIES—a name that evoked both power and precision. Introduced around 1985, the series was marketed as a “reference-grade” system aimed at serious audiophiles and professional studios. It was never mass-produced, and surviving units are exceptionally rare today, often passed quietly among collectors or restored by dedicated enthusiasts.

Technical Specifications

The TEMPEST-SERIES was a floor-standing hybrid planar loudspeaker, combining ESS’s signature quasi-ribbon drivers with conventional woofers to overcome the bass limitations inherent in planar designs. Each speaker featured a vertical array of drivers, housed in a tall, narrow cabinet with a sleek, minimalist aesthetic typical of high-end gear from the era.

Notably, the quasi-ribbon drivers used in the TEMPEST-SERIES were made with ultra-thin conductive filaments suspended in a magnetic field—similar in principle to Magnepan or Apogee designs, but with ESS’s proprietary tensioning and damping techniques. This allowed for faster transient response and lower intermodulation distortion compared to traditional dome tweeters.

The bass section utilized dual 10-inch woofers in a transmission-line configuration, which extended low-frequency response while minimizing port noise and group delay. This hybrid approach was key to the TEMPEST’s ability to deliver both the delicacy of planar mids and the physical impact of deep bass.

Sound Characteristics and Performance

The sonic signature of the ESS TEMPEST-SERIES was nothing short of transformative for listeners accustomed to conventional dynamic speakers. Its most celebrated attribute was imaging precision—instruments were rendered with laser-like focus, and the soundstage was expansive, deep, and layered with exceptional spatial resolution.

Midrange clarity was a standout feature. Vocals, in particular, were reproduced with uncanny realism—breaths, sibilance, and emotional nuance were all present in a way that few speakers of the era could match. The planar drivers’ lack of cone breakup and minimal moving mass contributed to an almost “disappearing” quality, where the speakers seemed to vanish acoustically, leaving only the music.

High frequencies were smooth and extended, avoiding the harshness sometimes associated with early ribbon or metal-dome tweeters. However, the TEMPEST was not a “bright” speaker—it leaned toward neutrality with a slight warmth in the upper mids, likely due to the crossover integration and cabinet damping.

Bass performance was solid for a hybrid planar, though it demanded a well-matched amplifier and room placement. The transmission-line woofers provided tight, articulate low end, but lacked the sheer slam of large sealed or ported dynamic designs. That said, the integration between the planar and cone drivers was remarkably seamless when properly set up.

Notable Features and Innovations

• Dual Quasi-Ribbon Arrays: The use of two vertically stacked planar drivers allowed for increased radiating surface and improved power handling, reducing distortion at higher volumes.
• Transmission-Line Bass: Uncommon in planar hybrids, this design choice enhanced bass control and reduced resonance.
• Point-Source Mid/High Array: The close vertical alignment of the planar drivers created a coherent wavefront, improving off-axis response and imaging stability.
• Hand-Wound Crossovers: Each unit featured individually assembled crossovers with premium components, reflecting ESS’s commitment to quality.

Common Issues and Maintenance

Owning a pair of TEMPEST-SERIES speakers today is a labor of love. Due to their age and limited production, several issues commonly arise:

• Diaphragm Sag: The thin conductive filaments in the planar drivers can degrade or sag over decades, leading to distortion or buzzing. Restoration often requires re-tensioning or replacement.
• Crossover Component Aging: Capacitors and inductors may drift in value or fail. Rebuilding the crossover with modern equivalents is often necessary.
• Woofers Wear: The 10" bass drivers, while robust, may suffer from surround deterioration. Re-foaming or reconing is typically required.
• Low Sensitivity and 4-Ohm Load: These speakers demand powerful, current-rich amplifiers. Tube amps or low-damping-factor solid-state units may struggle to control the bass.

Restoration specialists familiar with vintage planar speakers are rare, but communities like The Audio Circle and Audiokarma have documented successful rebuilds. Finding original parts is difficult, so many restorers use compatible drivers from Magnepan or custom-built replacements.

Current Market Value and Collectibility

Genuine ESS TEMPEST-SERIES speakers are extremely rare. Fewer than 200 pairs are believed to have been made, and most remain in private collections. When one does appear on the market—typically via eBay, Audiogon, or specialty forums—it often sells quickly to collectors.

As of 2024, unrestored pairs trade between $1,200 and $2,000, while fully restored units with upgraded crossovers and drivers can command $3,500 or more. Their value is driven more by historical significance and engineering interest than by widespread fame, making them a “sleeper” in the vintage audio market.

They are particularly prized by enthusiasts of planar magnetic technology and those seeking an alternative to the more common Magnepan or Apogee speakers of the era.

Conclusion: A Legacy of Innovation

The ESS TEMPEST-SERIES stands as a bold, underappreciated chapter in the history of high-fidelity audio. It was a speaker that dared to blend competing technologies in pursuit of a singular goal: transparency without compromise. While it never achieved the commercial success of its contemporaries, its influence can be seen in modern hybrid designs from companies like MartinLogan and Revel.

For the vintage audio enthusiast, the TEMPEST-SERIES is more than just a speaker—it’s a piece of audio archaeology, a testament to a time when innovation was driven by passion, not profit. Finding, restoring, and hearing a pair in full cry is a rare privilege—one that connects the listener not just to music, but to the very spirit of analog excellence.

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