SONY APM-8 (1979) | Esprit APM

 

The Sony APM-8 was actually the very first Esprit branded product to be introduced to the market by Sony in july 1979. This was only preceded by the APM-9 but, that had more like a prototype status. Sony's APM-8 is a decisive step in the development of high-quality loudspeaker systems. Among the numerous special features of this unique monitoring unit, the flat, square diaphragm of the loudspeaker system stands out. It characterizes a design principle that comes very close to the goal of absolute sound fidelity. The cone shape of the diaphragms of dynamic loudspeakers has some properties that are detrimental to their radiation pattern. Partial vibrations, the limited stiffness, and the influence of the cavity in front of the diaphragm cone (cavity effect) prevent ideal, piston-like movement of the diaphragm. Making the diaphragm stiffer or heavier would mitigate the effect of undesirable vibration modes, but would not eliminate the cause. Controlling the vibration behavior is simpler with a flat diaphragm, provided the diaphragm material meets high requirements. Sony has developed a flat diaphragm through extensive research programs that allows precisely piston-like movements without frequency turbulence or partial vibrations. Analysis of the dynamic behavior show that the diaphragms of the APM-8 are approximately 500 to 1000 times stiffer than conventional paper cone diaphragms. The stabilizing element of the flat diaphragm is a honeycomb-like aluminum structure, which is welded on both sides under high pressure to a thin film of carbon fiber or an aluminum alloy. The film material, core thickness, and structural rigidity are carefully matched to the frequency range to be reproduced by the individual transducers. The typical fluctuations in the sound pressure level of conventional cone loudspeakers are thus significantly reduced. The linear excursion of the APM-8 transducers is remarkably large. Deformations are practically eliminated. And since there is no cavity effect, the delicate phase relationships of the music signal remain undisturbed. Specifications: Frequency response 25-30.000Hz | Impedance 8oHm | Power rating 150/500W Sinus/Music | Size: 648x1105x495mm (W/H/D) | Weight 92kg | Original sale price in Germany 26.000 DM!!!...the price of a Mercedes-Benz 280E/280CE

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