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6 The Genesis 6.1 Technology
6.1 The Servo-bass Advantage
Very few loudspeakers use servo drive, either because most designers
think that it is too difficult to design, too expensive or because of the
extraordinary demands a servo system makes on the amplifier and the
transducer. However, the Chief Scientist of Genesis, Arnie Nudell, first
introduced the servo system in the legendary Infinity Servo Statik One in
1968(!) – so we know how to design and build servo systems.
The concept of the Genesis servo bass system is an easy one to
understand: It employs an accelerometer as a sensor, to constantly
monitor the movement of the woofer cone and instantaneously compare
it to the input signal. This comparison circuit identifies any deviation from
the input, and instantaneously applies a corrective signal to
compensate, thus practically eliminating the inherent distortion of the
woofer.
As an example, when you have a high-impact, low-bass signal that
starts and stops suddenly (for example a tympani), the inertia of the
woofer cone makes it slow to start moving, and then after it is moving,
the momentum of the cone makes it continue moving even after the
signal has stopped.
The sonic result is overhang, bloat, lack of tautness and definition, and a
blurring of dynamic impact.
With the servo system, the circuit senses that the woofer is not moving
as fast as it should and it instantaneously applies much more current to
make it move faster. When the signal stops, it detects that the woofer
will continue to move when it shouldn’t and applies a counter-signal to
stop woofer.
Open loop woofers are simply not capable of such accurate control and
response.
Thus, the servo-drive reduces distortion and improves transient
response by making the woofer seem massless. Typical non-servo
woofer systems have distortion levels that exceed 10% at even
moderate levels. The Genesis servo bass system reduces this distortion
to below one percent at almost any output level. It also drives the woofer
to constant acceleration which makes its frequency response flat.
The servo system is a more proactive approach to controlling a
loudspeaker than high-damping factor and high current in the amplifier.