ESS amt-1a

A loudspeakers translates electrical impulses into sound waves: Ideally,the loudspeakers/translator leaves nothing out and puts nothing extraneous in. It doesen't omit or color or mask. The perfect translator is perfectly simple. Simple and impossible until the Heil AirMotion Transformer revolutionized sound reproduction. The Heil midrange/high-frequency transformer is the perfect translator. There is only one compact system with a full-size Heil. The ESS amt-1a Bookshelf system. perfectly simple.

Your ears will appreciate the difference

Air-Motion Transformation: Midrange/High-Frequency

The Heil transformer, like most significant innovations, is much appreciated but a little mysterious. It is mandatory equipment for master reproduction techniques, yet the technological basis for its performance is often taken for granted. Actually, the Heil Principle of Air-Motion Transformation is as elegantly simple as it is effective.

The transformer's diaphragm resembles a lightweight pleated curtain mounted between powerful ceramic bar magnets. Conductive strips on the sides of each pleat cause the pleats to expand or contract in step with the signal. The air is squeezed out, and accelerated to five times the velocity of the diaphragm itself. In effect the Heil transformer uses air to move air, operating on the principle of pneumatic leverage.

Cone driving systems, on yhe other hand, are sluggish and inefficient by design. The cone's mass is huge, driving energy is largely devoted to overcoming its great inertia. The cone resonates and can "break up" at high frequencies. Acone driver only pushes air like a piston, in a one-to-one ratio.

The Heil driver's air-motion transformation ratio is five times better than that of any conventional speaker.

Other crucial design parameters are solved by the Heil Air-motion Transformer. The extremely light weight of its diaphragm eliminates resonance. Since the driving impulse is spread uniformly over the diaphragm surface, harmonic distortion from "cone breakup" is non-existent. These are inherent benefits of the Heilo design. For conventional speakers, they remain problematic goals.

REmarkable dispersion characteristics are another natural advantage of the amt's desugn. With a 120° pattern at 16 kHz, the amt maintains a solid expanse of stereo imagery to frequencies beyond audibility. Whatever the speaker/listener positioning, imaging is precise and penetrating.

The audible payoff is clarity, a perfect re-creation of the music 's fine and changing texture. Female vocal depth, the harmonic complexities of bow against string, and fleeting nuances of program ambience emerge with presence, immediacy, and power. It's all there.

Low Frequency performance

Deep, articulate low frequency response is provided by teh same 12" bass driver used in the top system of the ESS line, the amt-1a. Its 7 lb. 6,5 oz (3,36 kg) magnet assembly, rigid die-cast frame, and large-radius coil ensure state-of-the-art bass performance and dependability - response that feels substantial in the lower registers.

Power

The amt-1a Bookshelf system is designed to convert high power loads into clean; full sound, without effort and without distortion. The air-motion transformer's Teflon diaphragm both resists and dissipates heat outstandingly. The bass driver's 2" coil and high-temperature cone composition are significant factors in the system's low-end strength. "At power" the amt-1a Bookshelf is clear and dependable after other compact systems have reached their limits.

Dividing Network

The sophisticated crossover network designed for the amt-1a Bookshelf operates at 850 Hz, providing excellent woofer/amt phasing and precise signal distribution. Air-cored inductors are used to avoid the high-amplitude distortion possible with metal cored units. Altough air-cored inductors are an unseen refinement, they significantly enhance the linearity of a dividing network.

Controls

Your listening environment's acoustic character may prompt some fine adjustment of teh speaker system. A continuosly variable attenuation or accentuation control affects 850 Hz to beyond hearing, without blunting or peaking the higher frequencies and upper harmonics. The control panel is situated at the rear of the cabinet for easy access.

The construction of the amt-1a Bookshelf speaker enclosure reflects the same concern for distortion-free reproduction shown in the system's hardware. The interior dimensions of the enclosure are meticulously coordinated to the bass driver's specific characteristics. precise mathematical tuning determines port design.

Walnut veneer is matched, fitted to the cabinet superstructure, and hand-finished from sanding to final rubdown. A strong weave of sonically-transparent polyester fiber is used in the grille treatment, completing the speaker's appearance of simple, Functional grace.

The Final Arbiter

A classic integrity, from cabinetry to driver mounting detail, pervades the manufacture of the amt-1a Bookshelf. Its superiority can be demonstrated in many ways, reflected at lenght in technical data. But to the final arbiter, your ear, There is only proof. The audible proof. A critical evaluation of the amt-1a Bookshelf speaker system will reveal how perfect translation can be.

Specifications

Power Capacity: 75 watts continuous ; 350 watt peak Circuit breaker protected

Nominal Impedance: 4 ohms

Dispersion: 120 ° horizontal, 30° vertical

Crossover frequency: 850 Hz

Efficiency: 1 watt input produces 82 dB sound pressure at a distance of 15 feet (4 m)

Frequency Response: 50 - 20,000 Hz, ±3 dB

Heil Air-Motion Transformer

Total Radiating Area: 29 sq. in. (187,24 cm²)

Transformation Ratio: 5.0:1 velocity increase

Magnet Assembly Weight: 12 lbs. 15 oz. (5,87 kg)

Flux Density: 4,500 Gauss

Square Wave Rise Time: 15 microseconds at 5,000 Hz

Low Frequency Driver

Nominal Diameter: 12" (30,48 cm)

Voice Coil: 2" (5,08 cm)

Magnetic Assembly Weight: 7 lbs. 6,5 oz. (3,36 kg)

Flux Density: 10,500 Gauss

Controls

Midrange/High Frequency: Continuously variable attenuation oraccentuation from 1 kHz to beyond audibility

Decor

Finish: Oiled walnut veneer

Grille Color: Brown

Dimensions: 24" x 14" x 14" (60,96 x 35,56 x 35,56 cm)

Shopping Weight: 60 lbs (27,27 kg)

ESS amt-1b

Audible excellence is desired of every component in a high fidelity system. But the finest electronics can sound only as good as the loudspeakers they are played through. The newly refind and improved amt-1b Bookshelf owes its excellence largely to the Heil Air-motion transformer midrange-tweeter, the most revolutionary loudspeaker development of the past half-century. Unexcelled system coherency and balance is made possible by technically advanced crossover circuitry and newly improved low frequency system. Equal care in the construction of the handsome cabinet assures structural rigidity and acoustic superiority. The amt-1b Bookshelf is the finest bookshelf system ESS makes. Indeed, it is one of the finest in the world.

The Heil Air-motion transformer midrange-tweeter.

The remarkable Heil air-motion transformer is truly a monumental breakthrough in loudspeaker design, far superior to conventional cone drivers. The heil's light-weight Teflon diaphragm, equivalent in surface area to an eight inch midrange, is accordion-folded into a one inch pleated band. The diaphragm squeezes air between its pleats at five times its own speed, resulting in extremely swift air acceleration.

Each characteristic of the Heil contributes to an actual, audible superiority:

Its large driving area results in reduced distortion and increased dynamic range.

Folding this large area into a small point source results in superior dispersion and freedom from "boxiness".

The low mass of the lightweight diaphragm yields high efficiency and "instant acceleration".

High transformation, low diaphragm velocity and instant acceleration all lead to greater dynamic range and superb transients

The accordion-like pleats provide an evenly distributed drive. By preventing cone "break up", the pleats contribute to the Heil's great clarity and high definition.

The versatile amt-1b Bookshelf is the most compact system to incorporate the full-size Heil, the same one found in the incredible Transar/atd full-range Heil sound system by ESS. This newest version of the "Great" Heil offers a smoother, flatter response, owing to a new refinement in the folded "hinge" area of its diaphragm.

The superiority of the Heil air-motion trnsformer over conventional drivers is as dramatic as that of a jet aircraft over an old propeller plane. It is simply superior in too many ways and by too great a degree to be comparable.

The ESS Bextrene low frequency driver

Like the floor-standing 1b, the Bookshelf is equipped with an exceptionally rugged vacum-formed Bextrene low frequency driver newly improved and built entirely by ESS. Developed by BBC studio engineers for studio reference systems. Bextrene is a polystyrene compound with exceptional properties not found in pulp cones:

Low mass. High structural rigidity. Great internal molecular damping for superb quieting. Less susceptible to resonance and masking distortion. Greater clarity and accuracy.

Passive radiator

A rear-mounted 12" passive radiator operates in tandem with the Bextrene woofer to augment bass response. The passive radiator serves the same purpose as a port, but avoids the distortion added by a port or the loss of efficiency inherent in acoustic suspension systems.

Crossover circuitry and controls

Improved phase response, greater power handling capability and improved driver damping in the crossover region are all results of the 1b Bookshelf's completely new frequency dividing network. This sophisticated parallel type 1,000 Hz crossover assures proper matching of the woofer with the Heil by means of a steep 18 dB per octave slope.

The amt-1b Bookshelf now includes the same dual controls as the floor-standing system. They allow the listener to achieve precisely the midrange and high frequency performance desired.

Hand crafted cabinetry

The uncompromising performance of the amt-1b Bookshelf is also due in part to a cabinet design that is acoustically efficient as well as handsome. Each is made of select walnut veneers and is meticulously hand sanded, oiled and waxed to a silki sheen. An acoustically transparent rich brown grille provides the perfect finishing touch.

The amt-1b Bookshelf is, in every detail, the finest instrument ESS is capable of making in this convenient format. Keenly responsive faithfully accurate the 1b Bookshelf is the ultimate bookshelf system.

Specifications

Full System

Power Capacity: 375 watts (clean music power)

Nominal Impedance: 6 ohms minimum

Dispersion: 120 ° horizontal, 30° vertical

Crossover frequency: 1,000 Hz

Efficiency: 1 watt input produces 90 dB sound pressure at a distance of 1 m

Frequency Response: 40 - 23,000 Hz, ±3 dB

Controls

Presence/Brilliance: Continuously variable attenuation from +3 dB to -∞ from 1,200 Hz to beyond audibility

Heil Air-Motion Transformer

Total Radiating Area: 21,5 sq. in. (139 cm²) equivalent to an 8" cone

Square Wave Rise Time: 15 microseconds at 5,000 Hz

Transformation Ratio: 5,3:1 velocity increase

Magnet Assembly Weight: 12 lbs. 15 oz. (5,87 kg)

Flux Density: 4,500 Gauss

Low Frequency Driver

Nominal Diameter: 12" (30,48 cm)

Cone Materials: Bextrene

Voice Coil: 2" (5,08 cm) Copper bonded with high temperature epoxy to an aluminum former

Magnetic Assembly Weight: 7 lbs. 6,5 oz. (3,36 kg)

Flux Density: 10,500 Gauss

Insulation: Single polythermaleze

Passive Radiator

Nominal Diameter: 12" (30,48 cm)

Diaphragm Material: .5 in rigid EPS styrene foam base material laminated to a damping skin of 250" open cell foam . Unitary free air resonance: 5 Hz

Decor

Finish: Oiled walnut veneer

Grille Color: Black/Brown

Dimensions (H x W x D0: 24" x 14" x 14" (60,96 x 35,56 x 35,56 cm)

Shopping Weight: 65 lbs (29,48 kg)

Heil Air-Motion Transformer by ESS

Figure 1

The heart of the Heil air-motion transformer is a featherweight pleated Teflon diaphragm bonded with conductive aluminum strips. The diaphragm is suspended within a massive magnet structure. Its steel conductor plates concentrate an intense magnetic field around the diaphragm.

When a signal passes through the diaphragm's foil strips, the bellows-like motion of the pleats squeezes air out at five fimes the speed of the vibrating diaphragm itself. This virtual "instant acceleration" distinguishes the Heil from all other loudspeakers.

Figure 2

Polar response curves at a wide range of frequencies reveal a broad horizontal dispersion pattern through-out the audible spectrum. The ability of the Heil air-motion transformer to disperse even the highest frequencies over a large area assures full stereo imaging anywhere in the listening environment.

Figure 3

The superior response of the Heil air-motion transformer is revealed in its relatively flat impedance. The entire system's frequency response curve shows a typically broad, linear bandwidth. This exceptional efficiency at all frequencies permits the amplifier to deliver necessary power at ultrasonic frequencies.

Figure 4

A pair of drawings illustrates the movements of the Heil's pleats and the corresponding musical sine wave signals. In Figure 4A, the front facing pleats contract as the sine wave rises, forcing the air out under pressure. Meanwhile, the pleats opening towards the rear draw air in. When the sine wave reverses, as shown in Figure 4B, the pleats contract in the opposite direction.

Figure 5

The "squeezing" action of the heil diaphragm's pleats viewed in detail from above. As the pleat walls (A) squeeze together, they force a large amount of air to accelerate under pressure through a narrow opening (B). The folds are 5.3 times as deep as they are wide, resulting in a 430 percent increase in air velocity.