Speaker excursion control system

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to FIG.
1, there is shown a sound system which may be incorporated into a vehicle.
The system includes a power supply 10 coupled to the vehicle's battery 11 through conventional wiring to provide +V and -V voltages to supply power to the remaining circuit elements coupled as indicated by the associated terminals.
Furthermore, the power supply 10 provides, through output conductors 14 and 16, operating power to a current source power amplifier 100 by means of plus and minus 24 volt rails respectively.
The power supply 10 can provide this voltage from the vehicle's 12 volt battery 11 by employing a conventional switch mode DC/DC converter circuit.
The electrical system shown in FIG.
1 includes an audio signal source 20 which can be a tuner, compact disc player, tape player, or a conventional automotive stereo system which combines these three sound sources into a single unit.
The audio signal source 20 has an output terminal 22 supplying relatively low amplitude audio signals selected from the head end of the audio signal source (i.
e.
tuner, compact disc player or tape player).
The selected audio signals are applied through an input scaling resistor 25 to an input terminal 12 of a state-variable filter 30 which, as described in greater detail below in connection with the detailed circuit diagram of FIG.
2.
, determines the excursion limit for a given speaker.
The state-variable filter consists of an electronic circuit consisting of cascaded integrators and a summing block that combines input and feedback signals in the proper ratio to obtain a desired response.
The circuit is essentially an analog computer model of a desired transfer function.
In the present circuit, a two-integrator state-variable filter is used to model the driven spring-mass-damper system of the primary resonance of a loudspeaker.
The outputs of the summing block and two cascaded integrators, respectively model acceleration, velocity and displacement of the cone motion