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

In the mid-1980s, high-end audio was in a period of experimentation, and Electro-Static Sound (ESS) pushed loudspeaker design harder than most. The company was best known for its work with electrostatic and planar magnetic transducers. In 1985 it introduced the TEMPEST-LS-5, a loudspeaker that doesn't fit neatly into any category. It is less widely recognized than its more famous sibling, the ESS AMT-1, but it came from a time when audiophiles and engineers were trying to get past the limits of conventional cone drivers.

The TEMPEST-LS-5 was not another box speaker. It was a hybrid electrostatic system. It combined ESS's quasi-ribbon (AMT-inspired) midrange and tweeter with a powered bass section. The aim was the speed and transparency of electrostatics with the low-end authority of dynamic drivers. Production numbers were extremely limited and documentation is scarce. Surviving units and anecdotal reports from vintage audio enthusiasts describe 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.

Specification	Detail
Model	TEMPEST-LS-5
Manufacturer	ESS (Electro-Static Sound)
Year Introduced	1985
Type	Hybrid electrostatic / planar magnetic with powered bass
Driver Configuration	1 x ESS folded ribbon (AMT-type) tweeter, 1 x planar magnetic midrange, 2 x 8" dynamic woofers (powered)
Crossover Type	Active/passive hybrid (passive mid-tweeter, active bass)
Bass Amplification	Internal 100W RMS amplifier (class AB)
Frequency Response	38 Hz – 22 kHz (±3 dB)
Sensitivity	86 dB (2.83V/1m)
Nominal Impedance	8Ω (compatible with most tube and solid-state amplifiers)
Recommended Amp Power	50–150W (for mid/highs)
Dimensions (H×W×D)	72" × 18" × 16" (183 cm × 46 cm × 41 cm)
Weight	68 lbs (31 kg) per cabinet
Enclosure Type	Transmission line / hybrid sealed (bass section)
Inputs	Line-level RCA for bass amp, speaker-level for main drivers

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 sound of the TEMPEST-LS-5 is often described as ethereal, transparent, and highly detailed, which is typical of ESS's planar technology. The folded ribbon tweeter is a derivative of the famous ESS Heil Air Motion Transformer. It delivered very fast transient response and an extended, airy top end that could resolve subtle details 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.

The TEMPEST-LS-5 stood out most 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 is not as deep or thunderous as a modern subwoofer, but it was tight and well integrated. The 100W internal amp kept the woofers driven with authority. That avoids the common problem of underpowered electrostatics, where bass flubs during dynamic passages. The 38 Hz lower limit does mean 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.

Clean the panels regularly with a soft brush, and run the speakers in a dry, climate-controlled room. Keep them out of direct sunlight and away from heat sources, because 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 fans of hybrid speaker technology. People prize them for their sound and 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 never achieved the fame of the Quad ESL-57 or the MartinLogan CLS. At the time, 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 a sonic time capsule. Anyone willing to invest in restoration and maintenance gets a listening experience that is transparent, detailed, and emotionally engaging. It may not be practical by modern standards.

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.

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