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)
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