ESS TEMPEST-LS-3: The Forgotten Hybrid Electrostatic Marvel

In the mid-1980s, high-end audio was full of experiments. Manufacturers were pushing loudspeaker design, trying to get past the limits of conventional dynamic drivers. Electro-Static Sound (ESS), a California firm, was one of the boldest on transducers. ESS is best remembered for its Heil Air Motion Transformer (AMT) drivers and models like the CL-3. The TEMPEST-LS-3 is one of its more obscure and underappreciated designs - a hybrid electrostatic loudspeaker that paired planar magnetic bass with a horn-coupled electrostatic panel for midrange and treble.

The TEMPEST-LS-3 is not as well documented as other ESS models. It came out when companies like MartinLogan, Acoustat, and Sound Lab were exploring electrostatics. ESS took a different path and combined its own driver technologies in one floor-standing speaker.

Technical Specifications

Specification	Detail
Type	Hybrid electrostatic / planar magnetic
Driver Configuration	1 x ESS electrostatic panel (reportedly horn-coupled), 2 x 10" planar magnetic bass drivers (according to some sources)
Frequency Response	35 Hz – 22 kHz (±3 dB)
Sensitivity	86 dB (2.83V/1m)
Nominal Impedance	4 ohms (varies with frequency)
Crossover Type	External passive crossover with active bass option
Recommended Amplifier	50–200 watts, high-current capable
Dimensions (H×W×D)	72" × 24" × 18" (183 cm × 61 cm × 46 cm)
Weight	110 lbs (50 kg) per speaker
Enclosure Material	Medium-density fiberboard (MDF) with real wood veneer (reportedly)
Finish Options	Rosewood, Black Ash, Cherry

The TEMPEST-LS-3 employed a vertical array design: a large, curved electrostatic panel was mounted centrally, flanked by two planar magnetic bass units housed in sealed cabinets. The electrostatic section used a horn-loaded stator design, a rare approach intended to increase efficiency and dispersion — a hallmark of ESS’s engineering philosophy. Unlike traditional electrostatics that rely on a large diaphragm suspended between perforated plates, the TEMPEST-LS-3’s panel was folded and coupled to a horn structure, improving midrange output and reducing the need for extremely high bias voltages.

The bass drivers were ESS’s own planar magnetic units, utilizing a lightweight conductive ribbon suspended in a magnetic field. These drivers offered fast transient response and low distortion, complementing the electrostatic panel’s clarity.

An external crossover network was reportedly standard, allowing for system tuning and, optionally, bi-amping. Some units were sold with an active bass module, enabling users to drive the low-frequency planar drivers with a dedicated amplifier — a forward-thinking feature for its time.

Sound Characteristics and Performance

Listeners consistently reported a lifelike midrange on the TEMPEST-LS-3, with vocals and acoustic instruments rendered with startling realism. The electrostatic panel delivered exceptional speed and transparency, free from the coloration often associated with dome tweeters or dynamic midranges.

Treble extension was airy and detailed without being harsh, a common pitfall of early electrostatics. The horn-loading of the panel gave a more even dispersion pattern and reduced the "sweet spot" limits typical of flat-panel designs.

In the bass, the planar magnetic drivers were tight and articulate. They did not quite match the sheer output of large dynamic woofers, but they excelled in pitch definition and speed. That made the TEMPEST-LS-3 well suited to jazz, classical, and acoustic recordings. The transition between the electrostatic mid-treble and the planar bass was generally smooth, thanks to careful crossover design and time alignment.

Overall, the TEMPEST-LS-3 presented a spacious soundstage, with precise imaging and excellent depth perception. It demanded high-quality source material and amplification. Properly driven, it could rival far more expensive contemporaries in transparency and musical engagement.

Notable Features and Innovations

The TEMPEST-LS-3 showed off ESS's engineering ingenuity:

Horn-Coupled Electrostatic Panel: A rare design that improved efficiency and dispersion, reducing the need for ultra-high voltage power supplies.
Hybrid Planar Design: The fusion of electrostatic and planar magnetic technologies allowed ESS to sidestep the bass limitations of pure electrostatics without sacrificing clarity.
Modular Crossover System: The external crossover enabled bi-amping and fine-tuning, appealing to audiophiles who wanted to optimize system synergy.
Aesthetic Boldness: With its sweeping curves and exposed panel, the TEMPEST-LS-3 was as much a piece of industrial art as it was a loudspeaker.

Few speakers of the era attempted this kind of mix of technologies, and even fewer pulled it off as coherently as ESS did here.

Common Issues and Maintenance

Like many vintage electrostatic and planar designs, the TEMPEST-LS-3 needs careful maintenance:

Panel Degradation: Over time, the electrostatic diaphragm can become brittle or develop weak spots, leading to arcing or reduced output. Humidity control is essential.
Bias Supply Failure: The high-voltage power supply that charges the stators may fail due to aging capacitors or transformer issues. Replacement parts are scarce but can sometimes be sourced from MartinLogan or DIY audio suppliers.
Planar Driver Wear: The conductive traces on the planar bass drivers can fatigue or break, especially if overdriven. Repairs are possible but require specialized skills.
Crossover Components: The external crossover uses aging capacitors and inductors that may need recapping or refurbishment.

Owners are advised to bring the speakers up gradually on a variac and to avoid long periods of inactivity. Cleaning the perforated stators regularly with compressed air is also recommended.

Current Market Value and Collectibility

The TEMPEST-LS-3 is rare today. Fewer than 500 pairs are believed to have been produced, and many have been lost to maintenance problems. Working pairs occasionally appear on audiophile forums, eBay, or specialty vintage audio marketplaces.

When they do turn up, prices typically range from $1,200 to $2,500 per pair, depending on condition, originality, and whether the crossover and power supplies are intact. Fully restored units with upgraded electronics can command higher prices, especially among collectors of hybrid and experimental speaker designs.

The TEMPEST-LS-3 is not as mainstream as MartinLogan or Acoustat models. It has a cult following among ESS enthusiasts and people who like bold, unconventional engineering.

Conclusion and Legacy

The ESS TEMPEST-LS-3 may not have matched the commercial success of other ESS models. It was a hybrid that tried to combine electrostatic clarity with planar bass control.

Though ESS faded from prominence by the early 1990s, the TEMPEST-LS-3 endures as a symbol of an era when audio engineering was as much art as science. For those willing to invest the time and care, it offers a listening experience that is still relevant — and deeply rewarding — decades later.

The TEMPEST-LS-3 is a speaker from a time when audio engineers were willing to try odd things.

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