Patent ID: 7043032

Claim:
An audio-signal circuit, comprising: audio input and output terminals; a first series combination of two 2nd-order low-pass filters, the series combination having a first phase response, an input terminal coupled to the audio input terminal, and an output terminal; a second series combination of two 2nd-order low-pass filters and two 2 nd -order high-pass filters, the second series combination having a second phase response substantially equal to the first phase response, an input terminal coupled to the audio input terminal, and an output terminal; a third series combination of two 2nd-order high-pass filters, the third series combination having a third phase response substantially equal to the first and second phase responses, an input terminal coupled to the audio input terminal, and an output terminal; and a combining circuit having first, second, and third input terminals respectively coupled to the output terminals of the first, second, and third series combinations and having an output terminal coupled to the audio output terminal.