Not that long ago the team of Robin Audio informed us of their new innovative active loudspeaker called Oloron Oloron-Sainte-Marie. A quick glance at the speaker specs, and the pics, made me immediately react enthusiastically. I had several reasons to do so. First off, not that long ago I reviewed a loudspeaker from Elipson, another French speaker manufacture who, like Robin Audio, is fond of white and roundish speakers.
For example, the speaker is said to involve a motional feedback system MFB for the woofer. Second, and more surprisingly, the speaker is said to be current driven. The thorough and carefully argued book is a sort of Opus magnum in the field. Things being as they are, virtually all audio amplifiers and dynamic loudspeakers operate according to a voltage control formula.
This means that a low output impedance power amplifier that acts as a voltage source, tends to control the voltage applied to the speaker terminals, which voltage then causes current to flow to the driver. In this configuration, the amplifier kind of forces the voltage to follow the music signal no matter what the current flowing through the load is.
The situation is weird, as it should be clear to everyone that the current, and only the current, causes the cone of the dynamic speaker element to accelerate, which then generates sound. According to him, both technical reasons, and subjective listening impressions of the sound quality, strongly support the fact that the current drive of the speakers is clearly a better option.
What exactly is wrong with voltage control? The core problem is indeterminate electromotive forces induced in the voice coil that can freely distort the current in the voice coil.
