Patent Applications

The following applications have been filed in the UK:

GB2473921 (claiming priority from FI20090354):
COMPENSATION OF RISING FREQUENCY RESPONSE IN PASSIVE CURRENT-DRIVEN  LOUDSPEAKERS

ABSTRACT:
The sound quality of electro-dynamic loudspeakers can be very much improved by feeding the speaker drivers with a current signal instead of the conventional voltage signal. Current-mode is achieved, when the source impedance seen by the driver is high compared to the driver's own impedance. The problem is that, under current-drive, the rising frequency response of a typical cone-type speaker cannot be equalized simply by adding an RC-network in parallel with the driver because then the high source impedance is lost. In the presented solution is used a dual voice coil speaker driver together with a current dividing network that disables one of the voice coils at high frequencies, thus producing the required response correction while still preserving relatively high source impedance.

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GB2473950 (claiming priority from FI20090353):
PROTECTION CIRCUIT FOR CURRENT-DRIVEN LOUDSPEAKERS

ABSTRACT:
By driving an electro-dynamic loudspeaker with a current signal instead of the conventional voltage signal, one can achieve, in addition to superior sound quality, also better-performing protection against driver overloading. The power protection of a current-driven speaker can be accomplished dynamically and without breaking the operation by connecting, through a rectification bridge 2a-d, a power transistor 5 in parallel with the driver to be protected 1; the control voltage of said power transistor 5 being indicative of the voice coil warming in said driver 1. The voltage to be monitored may yet be filtered before rectification, so that the voltage would better represent the voltage dropped in the voice coil resistance.

DESCRIPTION
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