ESS

The Heil Air Motion Transformer — unlike anything else

History

ESS (ElectroStatic Sound Systems) was founded in 1972 in Sacramento, California. The company's raison d'être was to commercialize a revolutionary tweeter design invented by German physicist Dr. Oskar Heil—the Air Motion Transformer (AMT). Dr. Heil's AMT design was fundamentally different from traditional dome or cone tweeters. Rather than moving air directly with a piston-like motion, the AMT used a folded diaphragm that "squeezed" air, accelerating it through the folds to create sound. This resulted in exceptional transient response and detail retrieval that conventional designs couldn't match. The first ESS speaker, appropriately named the AMT1, debuted in 1972. Its distinctive pyramid-shaped cabinet housed the Heil AMT tweeter alongside a 10-inch ported woofer. The speaker's unique appearance and extraordinary high-frequency performance created an immediate sensation in the audio world. In 1977, Dr. Heil developed the ESS Transar, a full-range implementation of AMT technology. This ambitious design attempted to extend the AMT principle across the entire frequency spectrum—a challenging engineering feat that pushed the boundaries of speaker design. While ESS ceased manufacturing complete speakers in later years, the Heil AMT design continues to be manufactured and is used by numerous high-end speaker manufacturers today, testament to the enduring validity of Dr. Heil's innovation.

Key Facts

Fact	Detail
Founded	1972, Sacramento, California
Founder	ESS Corporation (licensed Heil's design)
Key Technology	Air Motion Transformer (AMT)
Inventor	Dr. Oskar Heil (German physicist)
First Product	AMT1 (1972)
Legacy	AMT design still widely used

Legendary Products

ESS AMT1 (1972)

The speaker that introduced the AMT to the world. Its distinctive pyramid cabinet housed a Heil AMT tweeter and 10-inch woofer. The AMT's lightning-fast transient response revealed details in recordings that other speakers obscured.

ESS AMT1 Tower / AMT1D (1970s-80s)

Larger floor-standing versions of the AMT1 with enhanced woofers and greater output capability. These became favorites among audiophiles seeking the AMT's clarity with more substantial bass.

ESS Transar (1977)

Dr. Heil's ambitious full-range AMT speaker, attempting to extend the air motion transformer principle across all frequencies. A rare and fascinating speaker for collectors.

ESS AMT Monitors

Professional studio monitors featuring Heil AMT technology found their way into recording studios, where their revealing nature helped engineers create better mixes.

Sound Signature

The Heil Air Motion Transformer produces high frequencies unlike any other driver technology. Instead of pushing air with a pistoning motion, the AMT squeezes air through folded diaphragm pleats, accelerating it to five times the diaphragm's own velocity. The result is transient speed that makes conventional dome tweeters sound sluggish by comparison. Cymbal strikes appear and decay with startling realism, vocal sibilants are rendered with microscopic precision, and the high-frequency detail retrieval is genuinely revelatory.

The AMT's speed also means these speakers are exceptionally revealing of source quality. Feed them a well-recorded acoustic album and you will hear the room around the musicians; feed them a compressed modern master and the AMT will tell you about every artifact. Paired with a quality woofer, the overall presentation is open, dynamic, and breathtakingly fast — the kind of sound that makes you re-examine recordings you thought you knew well.

Collecting ESS

The original AMT1 in its distinctive pyramid cabinet is the iconic ESS collectible — a speaker that looks as revolutionary as it sounds. The later AMT1 Tower and AMT1D floor-standing versions added more capable woofers and greater output, making them the practical choice for larger rooms. The Transar, Dr. Heil's ambitious full-range AMT speaker from 1977, is exceptionally rare and represents one of the most fascinating experiments in speaker history.

When buying vintage ESS speakers, the AMT driver itself is remarkably durable — the folded Kapton diaphragm rarely fails if it has not been physically damaged. The woofers, however, almost always need attention; foam surrounds deteriorate with age and replacement is straightforward. Many owners upgrade to modern woofers with better bass extension and power handling while keeping the original AMT, which remains the heart and soul of these speakers. The AMT technology has proven so enduring that numerous high-end manufacturers now use Heil-derived drivers in their current product lines.

Competitors & Comparisons

ESS vs Magneplanar: Both planar designs; ESS AMT, Magneplanar true ribbon ESS vs Acoustic Research: Different philosophies; ESS speed, AR accuracy ESS vs modern AMT speakers: ESS originals; many brands now license Heil's patent

Models

Amplifiers

TA-5650 — ESS TA-5650 integrated amplifier — 100W/ch Class-A statement piece, often paired with AMT-1 Heil speakers. Little else is documented.

Speakers

AMT 1-AM — ESS AMT 1-AM floor-standing speaker with Heil AMT tweeter and 12-inch paper woofer. Little documented; known for 9 dB drop at 11-12 kHz and transformer repair issues.
AMT 3 Rock Monitor — ESS AMT 3 Rock Monitor — 1970s floorstanding 3-way with the Heil air-motion transformer tweeter, 12-inch woofer, and 6-inch midrange.
AMT Monitor — ESS AMT Monitor bookshelf speakers from 1971 — 44 lbs each, Heil air-motion transformer tweeter with dipole radiation, 4-ohm impedance, walnut veneer cabinets.
AMT-1-TOWER (1978) — A pioneering full-range electrostatic hybrid tower speaker featuring ESS's innovative AMT technology. Find the complete spec table and when it was made here.
AMT-10 (1978) — A pioneering air motion transformer tweeter module from ESS, known for its speed, clarity, and innovative design. With full specifications.
AMT-10B (1978) — A pioneering electrostatic tweeter module using ESS's innovative Air Motion Transformer technology. This page has the complete spec table.
AMT-1B (1978) — The ESS AMT-1B is a pioneering air motion transformer tweeter module, celebrated for its clarity, speed, and innovative transducer design in high-end audio systems.
AMT-1C (1981) — A pioneering air motion transformer tweeter module designed for high-fidelity speaker integration. With when it was made.
AMT-4 (1978) — ESS AMT-4 two-way floor-stander (mid-1970s) with dual-magnetic-plate Heil AMT and 10-inch air-suspension woofer. Manual specs, fuse warning, and collector pricing.
AMT-6 (1978) — A high-end electrostatic tweeter module designed for integration into custom speaker systems, representing ESS's pioneering work in planar transducer technology.
AMT-7 (1978) — ESS AMT-7: A pioneering air motion transformer tweeter that redefined high-frequency clarity in vintage hi-fi systems. This page has the complete spec table.
AMT-8 (1982) — A high-end electrostatic speaker system from ESS featuring advanced AMT tweeter technology and hybrid design. This page has detailed specs.
AMT-Series (1978) — A pioneering series of high-end electrostatic and planar magnetic loudspeakers from ESS, known for their innovative Air Motion Transformer (AMT) tweeters.
CONNOISSEUR-SERIES AMT-450 (1985) — High-end electrostatic hybrid loudspeaker from ESS featuring AMT driver technology and planar magnetic design. Find the complete spec table here.
HEIL-AMT-MODEL-7 (1978) — A high-efficiency AMT tweeter module designed for integration into custom speaker systems, representing ESS's pioneering work in air motion transformer technology.
HEIL-AMT-MODEL-9 (1978) — An experimental electrostatic hybrid transducer system developed by ESS, representing early innovation in AMT driver technology.
HEIL-AMT-MONITOR (1978) — A rare and innovative electrostatic hybrid loudspeaker featuring the Heil Air Motion Transformer. This page has the complete spec table and when it was made.
Model 200 — ESS Model 200 stereo power amplifier from the Heil-era ESS stable — damping factor over 100 at 20 Hz, profiled by Audio in May 1974 and corrected that July.
PERFORMANCE-PS-4-A (1985) — A high-end passive speaker system from ESS known for its advanced driver technology and audiophile-grade sound reproduction.
PERFORMANCE-PS-5-A (1982) — ESS PERFORMANCE-PS-5-A — a high-end passive crossover designed for precision speaker integration in audiophile-grade systems.
PS-261 (1978) — A high-end passive crossover designed for use with ESS's legendary AMT drivers and speaker systems. With full specifications and production years.
PS-61 (1978) — The ESS Connoisseur PS-61 (1980s) is a compact floor-standing speaker kit with passive radiator design and impulse-correct engineering.
PS-62 (1985) — ESS PS-62 passive radiator system designed to enhance bass response in high-fidelity speaker setups. With detailed specs and production dates.
PS-81 (1978) — A rare and innovative electrostatic speaker system from ESS, representing early high-end hybrid audio design. This page has full specifications.
PS8A — ESS PS8A — obscure 2-way passive 8-inch professional PA / stage wedge speaker. Little documented beyond reseller listings; a later PS8A amp module appeared in Mix magazine in 2001.
TEMPEST-BOOKSHELF-CLASSIC (1985) — A rare and distinctive bookshelf speaker from ESS, blending advanced driver technology with compact design for high-fidelity sound.
TEMPEST-BOOKSHELF-I (1985) — A compact bookshelf speaker from ESS featuring the iconic Heil Air Motion Transformer tweeter, delivering detailed high-frequency response with dynamic clarity.
TEMPEST-BOOKSHELF-II (1985) — A compact bookshelf speaker from ESS featuring the legendary Heil Air Motion Transformer tweeter for exceptional high-frequency clarity.
TEMPEST-LS-1 (1985) — A rare and innovative electrostatic loudspeaker system from ESS, combining planar magnetic and electrostatic technologies for exceptional clarity and transparency.
TEMPEST-LS-2 (1985) — A high-end electrostatic loudspeaker system from ESS, known for its planar magnetic design and exceptional clarity. Covers detailed specs.
TEMPEST-LS-3 (1985) — A rare and innovative electrostatic hybrid loudspeaker from ESS, combining planar magnetic drivers with a unique horn-loaded electrostatic panel.
TEMPEST-LS-4 (1985) — A high-end electrostatic hybrid loudspeaker from ESS, combining planar magnetic and electrostatic technologies for exceptional clarity and imaging.
TEMPEST-LS-5 (1985) — A rare and innovative electrostatic loudspeaker system from ESS, blending planar magnetic and electrostatic technologies for exceptional clarity and imaging.
TEMPEST-LS-8 (1985) — A rare and innovative electrostatic loudspeaker system from ESS, blending planar magnetic and electrostatic technologies for exceptional clarity and imaging.
TEMPEST-SERIES (1985) — A rare and ambitious high-end loudspeaker series from ESS, featuring planar magnetic drivers and innovative hybrid design for exceptional clarity and imaging.
TRANSAR (1978) — ESS TRANSAR (1978) — the first full-range Heil air-motion loudspeaker system from ESS, 30 Hz–22 kHz ±3 dB, $3,250/pair. Little else documented.
TRANSAR-ATD-II (1985) — A rare and innovative electromagnetic speaker protection and transient correction device from ESS, designed to enhance dynamic loudspeaker performance and prevent damage.
TRANSAR-II (1985) — ESS TRANSAR-II — a rare and enigmatic audio processor from the mid-1980s, believed to be an experimental active crossover or room correction device from the legendary speaker manufacturer ESS.
TRANSAR-Series (1978) — A pioneering line of electrostatic speaker systems from ESS, known for their innovative hybrid design and ribbon-based tweeters.
Translinear (1975) — A pioneering active crossover and equalization system designed for high-fidelity multi-driver loudspeaker integration. Includes full specifications.
TRANSLINEAR-II (1977) — A groundbreaking hybrid electrostatic and dynamic loudspeaker system from ESS, combining planar clarity with bass driver efficiency.
TRANSSTATIC-1 (1978) — A revolutionary hybrid electrostatic and dynamic loudspeaker system from ESS, blending planar clarity with bass punch. With full specifications.
TRANSSTATIC-2 (1978) — A unique hybrid electrostatic/transducer loudspeaker system from ESS, blending planar clarity with dynamic driver efficiency.

Turntables

PS-4750 — ESS PS-4750 floor-standing 3-way loudspeaker, 100 dB sensitivity, 22 Hz–30 kHz response. Thinly documented; a 1976 Sony ad uses the same model number for a turntable.

Unknown

2240 — ESS Eclipse Model 2240 electronic crossover, c.1976. Reviewed in Audio July 1976; 7 crossover frequencies, 12 dB/octave slopes, rack-mount, $300.
PS-820 — ESS PS-820, an obscure ESS bookshelf speaker from around 1990. Little is documented; period listings suggest an 8-inch passive-radiator design with the Heil AMT.

Other Models

Heil Air Motion — ESS Heil Air Motion transformer speakers — Oskar Heil's folded-pleat AMT driver, 45 Hz–24 kHz, 4-ohm loads, and a lifetime transformer warranty.
PERFORMANCE PS 9 — ESS Performance PS-9 (1980–1982) — pyramid-shaped 2-way speaker with Heil AMT tweeter. Praised for clarity on tube amps, criticized for midrange gap.