ESS TEMPEST-LS-1: The Forgotten Electrostatic Innovator

In the mid-1980s, Electro-Static Systems (ESS) introduced a speaker that was different in design and in ambition. The ESS TEMPEST-LS-1 combined electrostatic and planar magnetic technologies, aimed at transparency, speed and realism. The Quad ESL-63 and the MartinLogan CLS got most of the attention. The TEMPEST-LS-1 is a rare, technically ambitious system that most people have forgotten.

A Legacy of Innovation

ESS was founded in the late 1970s by Ron Logan Sutherland. The company was known for pushing planar transducer design. It got early acclaim for its Heil Air Motion Transformer (AMT) tweeters, which offered exceptional transient response and low distortion. From there ESS moved into full-range electrostatic systems with the TEMPEST series, which ended with the TEMPEST-LS-1 around 1985.

A traditional electrostatic speaker uses a charged diaphragm suspended between perforated stator panels. The TEMPEST-LS-1 took a hybrid approach. It used a large-area electrostatic panel for the midrange and treble, and a separate planar magnetic bass section. The idea was to get around the limits of pure electrostatics, which are poor deep bass extension and limited dynamic headroom, while keeping their clarity and speed.

Technical Specifications

Specification	Detail
Model	TEMPEST-LS-1
Manufacturer	Electro-Static Systems (ESS)
Year Introduced	1985
Type	Hybrid electrostatic / planar magnetic loudspeaker
Frequency Response	45 Hz – 22 kHz (±3 dB)
Sensitivity	86 dB (2.83V/1m)
Nominal Impedance	4 ohms (electrostatic section), 6 ohms (bass section)
Crossover Type	External active crossover recommended
Bass Driver	Planar magnetic 12" x 2 (dual long-throw panels)
Mid/High Driver	Large-area electrostatic panel with Heil-type AMT bias
Recommended Amplification	50–200 watts (high-current preferred)
Dimensions (H×W×D)	78" × 24" × 16" (each)
Weight	85 lbs (38.5 kg) per speaker
Finish Options	Black textured vinyl, walnut veneer (rare)

The TEMPEST-LS-1 required high-voltage power supplies (typically ±1,500V) to charge the electrostatic panel, supplied via an internal or external bias generator. The planar magnetic bass section operated on conventional voice-coil principles but used lightweight, low-mass conductors embedded in a diaphragm, contributing to tight, articulate low-frequency response.

Sound Characteristics and Performance

The sound of the TEMPEST-LS-1 is best described as ethereal yet grounded. The electrostatic midrange and treble have the qualities audiophiles want: vanishingly low distortion, exceptional detail retrieval and a near-zero time smear. Violins, acoustic guitars and female vocals come through with startling realism, in a precise, three-dimensional soundstage.

The integration of bass is where the TEMPEST-LS-1 stood out. Many electrostatics of the era needed subwoofers or gave up low-end extension. The planar magnetic bass panels in the LS-1 gave a surprisingly dynamic and controlled foundation. They are not as deep or room-shaking as modern powered subwoofers. The bass was fast, articulate and well matched to the electrostatic panel, so it avoids the "two-part" sound that sometimes plagues hybrid designs.

Listeners often report a "see-through" clarity, a sense that the speakers disappear acoustically. The TEMPEST-LS-1 did well with chamber music, jazz trios and vocal recordings, where nuance and timing matter most. Like most high-sensitivity planar designs, they need quality amplification and careful room placement.

Notable Features and Innovations

The TEMPEST-LS-1 was packed with forward-thinking engineering:

Dual-Technology Design: The fusion of electrostatic and planar magnetic drivers in a single cabinet was rare and ambitious. ESS managed a smoother integration than many competitors by carefully matching the dispersion and transient behavior of both sections.

Heil-Inspired Biasing: While not a true Air Motion Transformer, the electrostatic panel used a variation of the Heil principle—corrugated diaphragms and high-velocity air displacement—to enhance efficiency and reduce mass.

Modular Construction: The speakers were designed with serviceability in mind. The electrostatic panel could be removed and replaced, and the bias supply was modular, easing repairs.

Low-Diffraction Cabinet: The tall, narrow profile and recessed driver layout minimized front-baffle interference, contributing to a clean, open sound.

Active Crossover Compatibility: Though passive crossovers were available, ESS encouraged active bi-amping—using separate amplifiers for the bass and electrostatic sections—to maximize control and dynamics.

Common Issues and Maintenance

Owning a pair of TEMPEST-LS-1s today takes work. These speakers are rare and fragile, and finding working examples takes patience and technical know-how.

Common issues include:

Bias Supply Failure: The high-voltage generator is prone to capacitor aging and transformer failure. Many units today require rebuilt power supplies.
Diaphragm Damage: The ultra-thin electrostatic diaphragm can tear or short out if exposed to excessive humidity, physical contact, or voltage spikes.
Stator Corrosion: Over time, the metal stator plates can corrode, especially in humid environments, leading to arcing or distortion.
Planar Panel Delamination: The bass panels may suffer from adhesive breakdown, causing flapping or buzzing at high volumes.

Restoration typically involves re-lacing or replacing the electrostatic panel, refreshing all electrolytic capacitors, and recalibrating the bias voltage. Original parts are scarce, so some owners turn to modern equivalents or custom rebuilds.

Current Market Value and Collectibility

The ESS TEMPEST-LS-1 is highly collectible but under-the-radar. Unlike more mainstream vintage speakers, it has not yet seen a surge in auction prices, which makes it a potential "sleeper" for savvy collectors.

Working pairs in good condition typically trade between $1,200 and $2,500, depending on restoration quality and finish. Fully restored units with upgraded bias supplies and modern protection circuits can command higher prices, especially among enthusiasts of hybrid planar designs.

Its rarity—fewer than 500 pairs are believed to have been made—adds to its allure. For those who appreciate engineering innovation and sonic purity, the TEMPEST-LS-1 offers a unique window into an alternative path in loudspeaker development.

Conclusion and Legacy

The ESS TEMPEST-LS-1 did not match the commercial success of its peers. While many manufacturers were refining conventional cone drivers in the 1980s, ESS blended two transducer technologies in one speaker.

Today, the TEMPEST-LS-1 is more than a relic—it’s a sonic time capsule. For the vintage audio explorer, restoring and listening to a pair is not just about nostalgia; it’s about experiencing a different philosophy of sound reproduction—one where speed, transparency, and realism are prioritized above all.

If you’re lucky enough to encounter a pair, don’t dismiss them as forgotten tech. Power them up (carefully), place them in a spacious room with attention to symmetry and clearance, and prepare to be surprised. The TEMPEST-LS-1 may be obscure, but for those who hear it, its storm is unforgettable.

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