Phase equalization for multi-channel loudspeaker-room responses
A system and method for minimizing the complex phase interaction between non-coincident subwoofer and satellite speakers for improved magnitude response control in a cross-over region. An all-pass filter is cascaded with bass-management filters in at least one filter channel, a[ 1 d preferably all-pass filters are cascaded in each satellite speaker channel. Pole angles and magnitudes for the all-pass filters are recursively calculated to minimize phase incoherence. A step of selecting an optimal cross-over frequency may be performed in conjunction with the all-pass filtering, and is preferably used to select an optimal cross-over frequency prior to determining all-pass filter coefficients.
1. A method in a signal processor for minimizing the spectral deviations in the cross-over region of a combined bass-managed subwoofer-room and bass-managed satellite-room response, the method comprising:
providing at least one second order all-pass filter having coefficients to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker, the all-pass filter being in cascade with at least one of the satellite speaker filter and subwoofer bass-management filter;
adapting the coefficients of the all-pass filter by minimizing a phase response error, the error being a function of phase responses of the subwoofer-room response, the satellite-room response, and the subwoofer and satellite bass-management filter responses.
2. The method of claim 1 , wherein processing a speaker channel with the all-pass filter comprises applying at the least one second order all-pass filter in a satellite channel level matching.
3. The method of claim 1 , further including the step of selecting a cross-over frequency to minimize spectral deviations in the cross-over region.
4. A method for minimizing the spectral deviations in the cross-over region of a combined subwoofer and satellite speaker response, the method comprising:
providing a structure for at least one all-pass filter to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker;
defining a phase response error for a combined subwoofer, all-pass filter, and satellite response;
obtaining coefficients for the all-pass filter by minimizing the phase response error; and processing a speaker channel with the all-pass filter.
5. A method for minimizing the spectral deviations in the cross-over region of a combined bass-managed subwoofer-room and bass-managed satellite-room response, the method comprising:
providing at least one second order all-pass filter having all-pass filter coefficients selectable to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker;
recursively computing the all-pass filter coefficients to minimize a phase response error, the phase response error being a function of phase responses of a subwoofer-room response, a satellite-room response, and the subwoofer and satellite bass-management filter responses; and
cascading the all-pass filter with at least one of the satellite speaker bass-management filter and subwoofer bass-management filter.
6. A signal processor configured to minimize the spectral deviations in the cross-over region of a combined bass-managed subwoofer-room and bass-managed satellite-room response, the configuration comprising a sub-configuration to:
provide at least one second order all-pass filter having coefficients to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker, the all-pass filter being in cascade with at least one of the satellite speaker filter and subwoofer bass-management filter;
adapting the coefficients of the all-pass filter by minimizing a phase response error, the error being a function of phase responses of the subwoofer-room response, the satellite-room response, and the subwoofer and satellite bass-management filter responses.
7. The signal processor of claim 6 , wherein the configuration further comprises a configuration to process a speaker channel with the all-pass filter by applying at the least one second order all-pass filter in a satellite channel level matching.
8. The signal processor of claim 6 , wherein the configuration further comprises a configuration to select a cross-over frequency to minimize spectral deviations in the cross-over region.
9. A signal processor configured to minimize the spectral deviations in the cross-over region of a combined subwoofer and satellite speaker response, the configuration comprising a sub-configuration to:
providing a structure for at least one all-pass filter to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker;
define a phase response error for a combined subwoofer, all-pass filter, and satellite response;
obtain coefficients for the all-pass filter by minimizing the phase response error; and process a speaker channel with the all-pass filter.
10. A signal processor configured to minimize the spectral deviations in the cross-over region of a combined bass-managed subwoofer-room and bass-managed satellite-room response, the configuration comprising a sub-configuration to:
provide at least one second order all-pass filter having all-pass filter coefficients selectable to reduce incoherent addition of acoustic signals produced by the subwoofer and the satellite speaker;
recursively compute all-pass filter coeffients to mimimize a phase response error, the phase response error being a function of phase responses of a subwoofer-room response, a satellite-room response, and the subwoofer and satellite bass-management filter responses; and
cascade the all-pass filter with at least one of the satellite speaker bass-management filter and subwoofer bass-management filter.