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CONTROLLED SOUND

 

SMART SPEAKER TECHNOLOGY

  • Adaptive software solution
  • Online learning with any audio signal
  • Using the transducer itself as a sensor
  • Compensation linear and nonlinear distortion
  • Active protection against overload
  • Identifies the safe range of operation automatically
  • More output at lower cost, less weight and smaller size

The control technology is based on a lumped parameter model, which considers the dominant nonlinearities inherent in a moving coil motor structure and in the mechanical suspension system. The controller is realized as an adaptive system requiring no additional input information from a human expert. The nonlinear force factor Bl(x), the stiffness Kms(x) and other transducer parameters reveal the thermal and mechanical limits of the permissible working range. The controller makes the internal state of the transducer transparent. An example of internal state would be voice coil temperature. The controller also reveals manufacturing tolerances, ageing of the material and the influence of external factors such as acoustical load, gravity and climate. This information is of high diagnostic value, which is important for use in safety equipment, professional applications and consumer audio. Digital preprocessing of the electrical input signal is used to equalize, linearize, stabilize and actively protect the transducer against overload.  

The control technology allows the exploitation of all hardware resources, which makes the transducer smaller, lighter and more cost effective. Sacrificing linearity in the motor structure for efficiency leads to a new generation of "green speakers" producing more acoustical output and less heat by requiring less energy.

The dominant nonlinear distortions are generated in a nonlinear feedback loop close to the electrical input of the transducer. The controller compensates for the distortion by using a nonlinear filter structure which is a mirror image of the transducer model.

The harmonic and intermodulation distortion synthesized in the mirror filter cancel out the distortion genereted by the transducer, thereby creating a linear relationship between control input z and sound pressure output p at any point r in the sound field.

The linear, nonlinear and thermal parameters of the transducer are permanently identified by monitoring input current and voltage at the electrical terminals of the speaker. The parameters are fed back to the audio processing and stored permanently in memory, where they are used as initial values when powering up the system.