Mondial Sub1

Desde 1978, AudioPro ha diseñado y fabricado altavoces que han merecido su reconocimiento en todo el mundo, especialmente dentro de la especialidad de subwoofers activos. La historia de los altavoces de Audio Pro comenzó con un producto único, el modelo B2.50, un subwoofer poco común que incorporaba un amplificador y un crossover activo. El B2.50 incorporaba la técnica ACE-Bass (amplificador controlado eufónico Bass). Se trata de una técnica patentada, diseñada para reproducir las frecuencias bajas de los pequeños recintos. El ACE-Bass en el B2.50 utilizaba altavoces subwoofer duales, controlados por servos para hacer los ajustes convenientemente. ACE-Bass fue inventado por Karl Erik Ståhl, un joven ingeniero sueco que centro su labor en conseguir unos graves de gran intensidad, sin estar por ello la caja acústica supeditada a grande volúmenes. La tecnología ACE-Bass fue presentada por vez primera en la 61ª Convención de la Sociedad de Ingenieros de Audio, de Nueva York en noviembre de 1978. La sorpresa entre los audiófilos fue considerable, y la calidad de AudioPro pasó a ser mundialmente reconocida. Especialmente impresionante eran los graves, que daban sensaciones sónicas que pocos habían experimentado fuera de la sala de conciertos. La tecnología ACE-Bass ha seguido desarrollándose durante todos estos años y actualmente se sigue utilizando en la fabricación de los subwoofers de AudioPro.

 Explicación en Inglés

ACE-BASS is an abbreviation for Amplifier Controlled Euphonic Bass.

A more tecnical description of ace-bass

In Elektronikvärlden (a Swedish hi-fi magazine) No. 8, 1988, Bertil Hellsten wrote a very good and instructive description of the ace-bass technology. Below is an abstract of the article:

 

General

There are many ways to accomplish good bass in a loudspeaker. One is to have a large cabinet and a large woofer.   In practice, the lower limit for a woofer is set by the lower resonance frequency, which can be lowered by increasing the membrane's mass. By adding weights, you can go lower and lower in frequency. But, at the same time, the speaker will respond increasingly slowly.  

In addition, the membrane's compliance and damping will no longer match, so the result isn't useful. To achieve a very low limiting frequency in a small woofer, a combination of mass, compliance and damping is needed, and this is impossible to achieve mechanically.  Audio Pro's solution - electronic mechanics Seen from the amplifier's point of view, the loudspeaker is an electrical component with its mechanical attributes transformed into electrical magnitudes. The mass corresponds to a capacitance, and the compliance to an inductance that is in parallel with the capacitance. The attenuation corresponds to a resistance that is in parallel with both of the above.  

 By adding more inductances, resistances and capacitances, one should easily be able to change the loudspeaker's mechanical attributes. This is the main idea behind Audio Pro's ace-bass loudspeaker constructions.    But there is a catch. The drive unit's voice coil has a resistance that lies serially with the parallel 'mechanical' components. This means that we can't parallel-connect directly to the woofer's mechanical parameters. It is not connected to the amplifier firmly enough.  If we were to increase the damping by parallel-connecting the amplifier output with a resistance, we would still never get a lower value than what the voice coil's resistance gives, and that is not good enough. The same thing happens to the other attributes. They are 'hidden' by the voice coil's (and the speaker cable's) resistance.  

Negative resistance


The solution is to serially connect the amplifier output with a negative resistance. But you can't buy that at your nearest electronics parts shop. It can only be achieved by positive feedback in the amplifier's output stage.   There are several sensitive factors that can easily cause the system to self-oscillate. However, correctly trimmed, you can achieve a system that exactly equalizes all the resistances that are in series with the drive units' properties. In this way, you can also reach and affect the loudspeaker's mechanical attributes electrically.  

 You can also choose to let this influence decrease with increasing frequency, where it's no longer needed.    By using this feature fully, Audio Pro maintains that you can decrease the speaker's physical volume by 90%, compared to a conventional bass reflex box!