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Active Stabilization of Voice Coil Position

  • Measurement of voice coil position
  • No mechanical sensor required
  • Active compensation of coil offset
  • Copes with production variance and aging
  • Maximum peak-to-peak displacement
  • More bass from smaller speakers

KCS detects the absolute position of the coil without a mechanical sensor by monitoring the input current and identifying an offset in the nonlinear curves. The detected offset can be actively compensated by supplying an appropriate DC voltage to the transducer via a DC-coupled amplifier. This ensures maximum positive and negative voice coil swing, giving maximum bass generated at high efficiency over the lifetime of the speaker.

For achieving maximum bass level, the peak-to-peak displacement must be maximized. This requires the voice coil being centered between the boundaries. However, the voice coil position is not stable because it depends on soft parts, which show high production variances and will change over time due to temperature, aging and other external influences like air pressure. In addition, transducer nonlinearities can cause dynamic voice coil position shifts due to instable behavior.

can compensate for all these influences.

Demo Video

Video: Static Voice Coil Offset Compensation

The video shows the detection and compensation of a static voice coil offset which is simulated by applying a small DC voltage to the speaker. In a first step a DC voltage is applied to the speaker without any compensation by KCS. The demonstration displays that KCS can detect the resulting voice coil offset. In a second step the automatic voice coil stabilization feature is activated and KCS applies a small DC voltage to push the voice coil back.

Video: Dynamical DC Compensation

Applying signals with high excursion the loudspeaker can create a dynamical DC in the voice coil rest position. This effect is shown in the video as well as the compensation of this generated DC by using KCS.