Automatically switched equalization circuit

DETAILED DESCRIPTION In the present invention, when an electrical connector is inserted into the subwoofer output jack, the insertion is sensed and automatically causes the necessary switches to be operated.
The activation of the switching means causes the low frequency drive to the smaller satellite speakers to be substantially reduced.
This allows the satellite speakers (which are normally quite small and tend to be weak at low frequencies) to operate in the mid range and high frequency range for which they are best suited.
In doing this, the power dissipation in the smaller satellite speakers is reduced dramatically due to the fact that they are no longer required to reproduce the low frequencies that are being fed to the subwoofer.
In many cases this is critical since a low-cost, low-current wall transformer is typically used to power the satellite amplifiers and therefore provides a limited supply voltage and current.
Due to the loading of the power supply when the amplifier reproduces low frequencies, the available output power for mid and high frequencies is substantially diminished thus causing distortion at all frequencies and inefficient use of the power supply.
The result of the present invention is louder and clearer sounding satellite speakers exhibiting a much lower tendency to clip the amplifier signals driving them due to a significant decrease in low frequencies.
In the present invention, a stereo minijack with a DPDT switch is used at the subwoofer output jack or connector.
When the subwoofer output jack or connector is unused (no plug inserted), the audio signal is caused by the DPDT switch in the jack to be routed such that full range frequencies are fed to the amplifier output sections and thence to the satellite loudspeakers.
When the subwoofer output jack is used (plug inserted), the audio signal is caused by the DPDT switch in the jack to be routed such that only mid range and high frequencies are fed to the amplifier output sections and satellite speakers.
The amplifiers and power supply for the satellite speakers are no longer subject to the low frequencies which will now be reproduced by the subwoofer through the plug inserted in the output jack