Audio Database


ESS amt1
119,000yen(one-set , around the 1973 time)

The floor type speaker system carrying the original unit called a heil driver.
amt is the abbreviation for "Air Motion Transformer".

The heil driver was an electrostatic type kind, is based on the principle "which makes air compress and emit and reproduces sound", and was developed by Dr. Oscar Heil of the Heil science laboratory in the United States.
This unit has about 5.5kg ferrite magnet and structure which placed the element into the magnetic field constituted by lamination pole piece. This element is the shape of accordion pleats which the covering with the optimal dumping characteristic of a macromolecule can expand and contract freely.
The electric conduction belt is embedded on the pleat, the pleat which faced each other when signal current flowed pays well, and air in it is compressed and emitted. The next pleat spreads conversely and inhales air from the opposite side. As for the remaining half-cycle, this motion operates completely conversely in a half-cycle.
This pleat is summarized to 17, when it is made into area, it is large in 2 and about 230mm, and it has acquired efficiency higher than a horn loudspeaker by operation which moreover compresses and emits air.
The characteristic in which the heil driver was excellent with this structure has been acquired, and also sound was diffused by the pole piece from which the front and the rear surface are completely symmetrical structures, and have become a wide angle, and the extensive directivity near indirectivity is realized.
Moreover, the element part has realized 20 microseconds and a very early standup at 5kHz on the structure by the covering (0.012mm) of a low-mass macromolecule.

The 25cm corn type Woofer is adopted as low-pass.
Especially, the dumping characteristic and a low distortion are thought as important and it is designed respond to the characteristic of a heil driver.

In order to unite with an indoor acoustic feature, the Attenuator of a three-step change is carried.
600Hz or more can be switched to Bright, Normal, and Soft at a 2dB step.

Even if a sudden unusual input is added during a drive, a speaker is protected with a built-in fuse.

The enclosure for Woofers is built by high density material, thought dumping and diffusion of low-pitched sound as important, and has adopted the bass-reflex system. Furthermore, the minimum sound is dumped with a sound-absorbing material, and is emitted to the back from the duct at the bottom of a cabinet.
The exterior has adopted the unique saran network which thought the directivity of the heil driver as important and with which it was walnut finishing, and the fifth page was covered.

Enclosure Input

Rating of a mode
System 2 ways, 2 speaker bass-reflex system, and a floor type
Use unit For low-pass: 25cm corn type
For high regions: Heil driver (electrostatic type)
Frequency response 45Hz-24kHz±2dB
Input impedance 4ohms
Distortion (it is 1m and sound pressure o'clock of 90dB from SP) 24kHz [ 600Hz - ] : 0.5%
600Hz [ 60Hz - ] : 1%
Square-pulse build up time 20 microseconds (5kHz)
Allowable input 350W (peak input)
Crossover frequency 600Hz
Dimensions Width 362x height 787x depth of 362mm