||Feedback Linearisation Of Low Frequency Loudspeakers
||Agerkvist, Finn T. (Acoustic Technology, Department of Electrical Engineering, Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark)
||Technical University of Denmark, DTU, DK-2800 Kgs. Lyngby, Denmark
||A loudspeaker is a device which produces sound. The sound pressure produced is due
to the movement of diaphragm. This movement is a result of an electrical signal applied
to the loudspeaker terminals. The movement of the loudspeaker can be described by a
mathematical model, which predicts its behavior with time. For low input signals, or
low levels, this behavior is fairly linear and a very good description is achieved with
linear differential equations. At high levels, the linear model fails due to the nonlinear
behavior in the loudspeaker.
This project focuses on the nonlinear behavior in a loudspeaker and how, if possible,
it can be reduced. The loudspeaker driver is studied and a mathematical model of the
loudspeaker is implemented where the nonlinearities are incorporated. With the model,
a control scheme is derived based on known control theory and technique. These are
the feedback and feedforward techniques.
The method used here is the classical closed loop feedback system. It utilizes a measured
output signal of a system which is fed back to the input where it is to be controlled.
Meaning, the output of the system is to follow a reference input of the system by means
of subtracting the output from the input and produce a so called error signal.
This error signal is then fed through a gain which amplifies the error signal. If the output
signal is distorted, then the error signal will be an inverted version of the output
signal (in theory), depending on how much feedback gain is possible. In principle, this
should cancel out the nonlinearities in the loudspeaker, and produce a non-distorted
The output signal is the loudspeakers acceleration, which is proportional to the input
voltage. This signal is obtained from an accelerometer, which is mounted on the loudspeaker
||Technical University of Denmark (DTU) : Kgs. Lyngby, Denmark
Creation date: 2009-09-07
Update date: 2009-11-04