Cross-over frequency selection and optimization of response around cross-over
First Claim
1. A method for selecting a cross-over frequency to attenuate a spectral notch in a cross-over region, the method comprising:
- measuring a full-range subwoofer and satellite speaker response in at least one position in a room;
selecting a cross-over region;
selecting a set of candidate cross-over frequencies and corresponding bass-management filters for the subwoofer and the satellite speaker;
applying corresponding bass-management filters to the full-range subwoofer and satellite speaker response to obtain bass managed subwoofer and satellite speaker responses;
level matching the bass managed subwoofer and satellite speaker responses to obtain leveled subwoofer and satellite speaker responses;
summing the leveled subwoofer and satellite speaker responses to obtain a net bass-managed subwoofer and satellite speaker response;
computing an objective function using the net bass-managed subwoofer and satellite speaker response for each of the candidate cross-over frequencies; and
selecting the candidate cross-over frequency resulting in the lowest objective function.
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Abstract
A system and method provide at least a single stage optimization process which maximizes the flatness of the net subwoofer and satellite speaker response in and around a cross-over region. A first stage determines an optimal cross-over frequency by minimizing an objective function in a region around the cross-over frequency. Such objective function measures the variation of the magnitude response in the cross-over region. An optional second stage applies all-pass filtering to reduce incoherent addition of signals from different speakers in the cross-over region. The all-pass filters are preferably included in signal processing for the satellite speakers, and provide a frequency dependent phase adjustment to reduce incoherency between the center and left and right speakers and the subwoofer. The all-pass filters are derived using a recursive adaptive algorithm.
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Citations
20 Claims
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1. A method for selecting a cross-over frequency to attenuate a spectral notch in a cross-over region, the method comprising:
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measuring a full-range subwoofer and satellite speaker response in at least one position in a room;
selecting a cross-over region;
selecting a set of candidate cross-over frequencies and corresponding bass-management filters for the subwoofer and the satellite speaker;
applying corresponding bass-management filters to the full-range subwoofer and satellite speaker response to obtain bass managed subwoofer and satellite speaker responses;
level matching the bass managed subwoofer and satellite speaker responses to obtain leveled subwoofer and satellite speaker responses;
summing the leveled subwoofer and satellite speaker responses to obtain a net bass-managed subwoofer and satellite speaker response;
computing an objective function using the net bass-managed subwoofer and satellite speaker response for each of the candidate cross-over frequencies; and
selecting the candidate cross-over frequency resulting in the lowest objective function. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. A method for attenuating an incoherent addition of satellite speaker and subwoofer acoustic signals, the method comprising:
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measuring the full-range subwoofer and satellite speaker response in at least one position in a room;
selecting a cross-over region;
selecting a set of candidate cross-over frequencies and corresponding bass-management filters for the subwoofer and the satellite speakers;
applying the corresponding bass-management filters to the subwoofer and satellite speaker full-range response;
level matching the bass managed subwoofer and satellite speaker response;
summing the subwoofer and satellite speaker response to obtain a net bass-managed subwoofer and satellite speaker response;
computing an objective function using the net bass-managed subwoofer and satellite speaker response for each of the candidate cross-over frequencies;
selecting the candidate cross-over frequency resulting in the lowest objective function;
filtering speaker signals using the selected cross-over frequency and corresponding bass-management filters; and
performing all-pass filtering on the filtered speaker signals to further attenuate spectral notches. - View Dependent Claims (16)
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17. A method for selecting a cross-over frequency to attenuate a spectral notch in a cross-over region, the method comprising:
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measuring a full-range subwoofer and satellite speaker response in at least one position in a room;
selecting a cross-over region;
selecting a set of candidate cross-over frequencies and corresponding bass-management filters for the subwoofer and the satellite speaker;
applying corresponding bass-management filters to the full-range subwoofer and satellite speaker response to obtain bass managed subwoofer and satellite speaker responses;
level matching the bass managed subwoofer and satellite speaker responses to obtain leveled subwoofer and satellite speaker responses;
summing the leveled subwoofer and satellite speaker responses to obtain a net bass-managed subwoofer and satellite speaker response;
computing an objective function using the net bass-managed subwoofer and satellite speaker response for each of the candidate cross-over frequencies;
selecting the candidate cross-over frequency resulting in the lowest objective function;
following selecting the cross-over frequency, further attenuating variations in the cross-over region by;
defining 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. - View Dependent Claims (18, 19, 20)
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Specification