|The SA 8535 Ribbon Compact Driver Since it started at the beginning of the 20th century, the audio industry has always been searching for new methods of achieving the best possible reproduction of the audible frequency spectrum.
In the early years, the radio industry was the great driving force behind innovations. But it was not until the FM-band was introduced (not so very long ago) that “high fidelity” broadcasting could be considered. But for professional audio technology the emerging film-industry was much more important. After all, the sound system had to be suitable for large groups of people and, for those days, high demands were also made on the high fidelity of sound. So it is no surprise that it was precisely this industry which provided major progress.
But the engineers of those days obviously did not leave it at that. A scientific article was published as early as 1920 in which this problem was solved. An “acoustic transformer” was invented which would “couple” the heavy cone mass via a so-called horn to a larger air-mass which improved the proportion mentioned above and considerably increased the efficiency. These horns are still used today.
The principle is simple. The loudspeaker is coupled to a chamber with a very narrow opening. As the cross-section of this opening is less than the cross-section of the loudspeaker, compression is induced in the chamber when the cone moves. This small opening in turn is coupled to the above mentioned horn but now at an even higher ratio and with larger final cross-sections. The result is even higher efficiency. In the years before the Second World War, this combined system also made it possible to generate an adequate acoustic output using a low amplifier output.
But then there is the old saying “Nothing ´s for free”. Here too. The compression mechanism adds additional distortion and the mechanical construction clearly limits the maximum output. Compression drivers therefore tend to sound irritable at high outputs (professional loudspeakers are generally used at the limit of their maximum output in practice; Distortion figures of some 25% are then customary).
The SA 8535 Compact Driver
In 1983 Stage Accompany started an ambitious project with the aim of making a different type of loudspeaker suitable for professional applications. This was based on one fundamental consideration.
The present amplifier output must allow the development of the high-tone loudspeakers which no longer use the compression mechanism, to produce a pure sound, particularly at the customary high outputs.
Ten years of development activities have finally resulted in the SA 8535 Compact Driver. An unparalleled new type of medium and high-tone loudspeaker. The SA 8535 is a patented ribbon type loudspeaker without the drawbacks of conventional compression drivers:
The special and simple design of the SA 8535 is probably the most important reason for the unprecedented sound quality produced by this ribbon type loudspeaker. Moreover, the recent development of new magnet material and cast-iron plastic film has contributed to the creation of the SA 8535.
No compression mechanism
Compression drivers are provided with the compression mechanism mentioned above. The SA 8535 Compact Driver operates without this compression space. The “diaphragm” in the Compact Driver generates the sound and transfers it directly to the ambiance. This results in an extremely pure, undistorted sound and much better reproduction of the highest frequencies. The concept of “listening fatigue” no longer occurs with Compact Drivers!
Direct Drive diaphragm
One of the striking differences between Compact Drivers and compression drivers is the method by which the diaphragm is driven. In compression drivers the forces are generated by the voice coil which are subsequently transmitted to the relatively heavy, poorly controllable, dome-shaped diaphragm with a 4-inch diameter. In Compact Drivers the voice coil and the diaphragm are integrated. This is a much simpler principle which produces enormous weight-savings (approximately 80%). This integration prevents the occurrence of the so-called “break-up phenomenon”-the most difficult phenomenon to be suppressed in loudspeaker technology. Break-up occurs when some parts of the diaphragm can no longer follow the forces applied to them. The diaphragm then starts to vibrate at random. This leads to aggravating and irritating reproduction. The SA 8535 Compact Driver is the unrivalled winner in the field of clarity and dynamic reproduction and leaves the compression driver far behind in performance.
Spectral decay plot for the Ribbon Compact Driver , the SA 8535.
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