Patent ID: 7466830

Claim:
An equalizing circuit comprising: an input unit for receiving a signal subject to a process; a high-frequency retrieving unit for retrieving, from the input signal, a signal at a frequency equal to or higher than a first cutoff frequency determined on the basis of a marginal frequency of a speaker provided at a back end; a low-frequency retrieving unit for retrieving, from the input signal, a signal at a frequency equal to or lower than a second cutoff frequency determined on the basis of the first cutoff frequency and of a frequency of audio signal to be reproduced by the speaker, in accordance with an attenuation slope for removing components at frequencies equal to or higher than the frequency of the audio signal to be reproduced by the speaker; an amplifying unit for amplifying the retrieved signal at a frequency equal to or lower than the second cutoff frequency; a synthesizing unit for synthesizing the amplified signal and the retrieved signal at a frequency equal to or higher than the first cutoff frequency, wherein said low-frequency retrieving unit comprises: a first low-pass filter for transmitting a signal at a frequency equal to or lower than a frequency which is lower than the second cutoff frequency, using a first filter order smaller than the filter order corresponding to the attenuation slope; a second low-pass filter for transmitting a signal at a frequency equal to or lower than a frequency which is higher than the second cutoff frequency, using a second filter order larger than the first filter order, and wherein the input signal is transmitted through the first low-pass filter and then the second low-pass filter.