ESS TEMPEST-LS-5: The Forgotten Hybrid Electrostatic Masterpiece

In the mid-1980s, as high-end audio entered a golden era of experimentation and innovation, few companies pushed the boundaries of loudspeaker design quite like Electro-Static Sound (ESS). Best known for their pioneering work with electrostatic and planar magnetic transducers, ESS introduced the TEMPEST-LS-5 in 1985—a bold, ambitious loudspeaker that defied easy categorization. Though not as widely recognized as its more famous sibling, the ESS AMT-1, the TEMPEST-LS-5 remains a fascinating artifact of a time when audiophiles and engineers alike sought to transcend the limitations of conventional cone drivers.

The TEMPEST-LS-5 was not merely another box speaker. It was a hybrid electrostatic system that combined ESS’s signature quasi-ribbon (AMT-inspired) midrange and tweeter with a powered bass section, aiming to deliver the speed and transparency of electrostatics with the low-end authority of dynamic drivers. While production numbers were extremely limited and documentation is scarce, surviving units and anecdotal reports from vintage audio enthusiasts paint a picture of a speaker that was ahead of its time—both technically and sonically.

Technical Specifications

Despite the lack of comprehensive factory brochures or service manuals, the TEMPEST-LS-5’s design has been pieced together through owner reports, technical forums, and comparisons with other ESS models of the era.

The TEMPEST-LS-5 employed a vertical array design: the electrostatic/planar panel occupied the upper two-thirds of the slender tower, while the bass drivers were housed in a separate, sealed compartment at the base—each equipped with its own built-in amplifier. This allowed the low frequencies to be driven independently, reducing intermodulation distortion and improving overall system coherence.

Sound Characteristics and Performance

The sonic signature of the TEMPEST-LS-5 is often described as ethereal, transparent, and highly detailed—hallmarks of ESS’s planar technology. The folded ribbon tweeter (a derivative of the famous ESS Heil Air Motion Transformer) delivered lightning-fast transient response and an extended, airy top end that could resolve subtle nuances in recordings with startling realism.

The planar magnetic midrange offered exceptional clarity and low distortion, rendering vocals and acoustic instruments with a lifelike presence. Unlike traditional cone drivers, the large surface area of the planar element moved air more uniformly, reducing breakup modes and coloration.

Where the TEMPEST-LS-5 truly distinguished itself was in its spatial performance. Owners frequently report a wide, stable soundstage with precise imaging and excellent depth cues. The vertical dispersion pattern contributed to a "holographic" listening experience, particularly when seated at the optimal height.

The powered bass section, while not as deep or thunderous as modern subwoofers, was remarkably tight and well-integrated. The 100W internal amp ensured that the woofers were always driven with authority, avoiding the common pitfall of underpowered electrostatics where bass flubs during dynamic passages. However, the 38 Hz lower limit means that organ pedals or electronic music with sub-bass content may not be fully reproduced—this is a speaker for nuance, not raw power.

Notable Features and Innovations

The TEMPEST-LS-5 was packed with forward-thinking design choices:

• Hybrid Active-Passive Architecture: One of the earliest consumer speakers to integrate an internal amplifier for bass while leaving the mids and highs to be driven by the main amplifier. This foreshadowed modern active speakers and bi-amped systems.
• ESS Folded Ribbon Technology: Derived from Oskar Heil’s AMT design, the tweeter compresses air in a pleated diaphragm, offering higher efficiency and lower mass than domes.
• Modular Construction: The bass module could theoretically be upgraded or replaced, a rare feature in 1980s speakers.
• Low-Distortion Crossover: The passive network for the planar drivers used high-quality components and was carefully tuned to preserve phase coherence.

Common Issues and Maintenance

As with any 40-year-old electrostatic or planar design, the TEMPEST-LS-5 requires careful attention:

• Capacitor Aging: The internal bass amplifier uses electrolytic capacitors that may dry out over time. A full recapping is recommended for units that have been powered off for years.
• Panel Degradation: The planar and ribbon elements are sensitive to humidity and physical damage. Tears in the diaphragm or misaligned stators can cause distortion or silence.
• Power Supply Failures: The internal amp relies on a custom transformer and rectifier. These can fail silently, leaving the bass section dead while the highs still work.
• Hard-to-Find Parts: Replacement panels or amplifiers are not commercially available. Owners often rely on DIY repairs or scavenging parts from donor units.

Regular cleaning with a soft brush and operation in a dry, climate-controlled environment are essential. Avoid placing the speakers in direct sunlight or near heat sources, as thermal expansion can warp the delicate panel frames.

Current Market Value and Collectibility

The ESS TEMPEST-LS-5 is extremely rare. Fewer than 500 pairs are believed to have been made, and even fewer survive in working condition. They occasionally appear on audiophile forums, eBay, or specialty vintage audio marketplaces.

In excellent, fully functional condition, a pair can fetch between $1,800 and $3,000. Units with known issues or non-working bass sections may sell for as little as $800–$1,200, primarily to collectors or restorers.

Despite their obscurity, the TEMPEST-LS-5 has a cult following among ESS enthusiasts and lovers of hybrid speaker technology. They are prized not just for their sound, but as engineering curiosities—a bridge between the electrostatic idealism of the 1970s and the powered speaker revolution of the 2000s.

Conclusion and Legacy

The ESS TEMPEST-LS-5 may never have achieved the fame of the Quad ESL-57 or the MartinLogan CLS, but it stands as a testament to a daring moment in audio history. At a time when most manufacturers were refining cone drivers, ESS was experimenting with radical transducer technologies and hybrid architectures that would take decades to re-emerge in mainstream high-end audio.

Today, the TEMPEST-LS-5 is more than just a speaker—it’s a sonic time capsule. For the intrepid audiophile willing to invest in restoration and maintenance, it offers a listening experience that is uniquely transparent, detailed, and emotionally engaging. It may not be practical by modern standards, but for those who value innovation and purity of sound, the TEMPEST-LS-5 remains a hidden gem of the vintage audio world.

If you’re lucky enough to encounter a working pair, give them a listen. You might just hear the future—35 years in the past.

eBay Listings

ESS Tempest LS-5 Speaker Review,Power Ring! 2 pgs, 1977

$9.99

VINTAGE ESS TEMPEST Air Motion Transformer Ribbon Tweeters

$145

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