Heyser spiral low frequency correction of FIR filters
First Claim
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1. A method of operating a loudspeaker, the method including:
- providing a digital audio signal;
identifying a target transfer function to be applied to the signal;
generating at least one coefficient of an FIR filter, the generating including performing Heyser spiral curve fitting, and fitting a three-dimensional curve based on a magnitude and phase of the target transfer function;
filtering the digital audio signal through the FIR filter; and
inputting the filtered signal into the loudspeaker.
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Abstract
A method of operating a loudspeaker includes providing a digital audio signal and identifying a target transfer function to be applied to the signal. At least one coefficient of an FIR filter is generated. The generating includes performing Heyser spiral curve fitting, and fitting a three-dimensional curve based on a magnitude and phase of a target transfer function. The digital audio signal is filtered through the FIR filter. The filtered signal is inputted into the loudspeaker.
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Citations
18 Claims
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1. A method of operating a loudspeaker, the method including:
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providing a digital audio signal; identifying a target transfer function to be applied to the signal; generating at least one coefficient of an FIR filter, the generating including performing Heyser spiral curve fitting, and fitting a three-dimensional curve based on a magnitude and phase of the target transfer function; filtering the digital audio signal through the FIR filter; and inputting the filtered signal into the loudspeaker. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of operating a loudspeaker, the method including:
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providing a digital audio signal; selecting a frequency below which an FIR filter is to be corrected; fitting magnitude and phase of a frequency response of the filter by separate low-order polynomial functions below the selected frequency, the magnitude and phase of the frequency response of the filter converging to a calculated transfer function above the selected frequency; filtering the digital audio signal through the FIR filter; inputting the filtered signal into the loudspeaker; and identifying a target transfer function to be applied to the signal, the providing step including generating at least one coefficient of the filter, the generating including performing Heyser spiral curve fitting, and fitting a three-dimensional curve based on a magnitude and phase of a target transfer function. - View Dependent Claims (9, 10, 11)
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12. A method of operating a loudspeaker, the method including:
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providing a digital audio signal; selecting a frequency below which an FIR filter is to be corrected, the selecting step including determining a frequency at which there is a difference between a target transfer function value and an actual transfer function value for the FIR filter that exceeds a threshold value; fitting magnitude and phase of a frequency response of the filter by separate low-order polynomial functions below the selected frequency, the magnitude and phase of the frequency response of the filter converging to a calculated transfer function above the selected frequency; filtering the digital audio signal through the FIR filter; and inputting the filtered signal into the loudspeaker. - View Dependent Claims (13)
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14. A loudspeaker arrangement comprising:
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a loudspeaker having an input; and a digital FIR filter having an input and an output, the input of the filter being configured to receive an audio signal, the output being coupled to the input of the loudspeaker, coefficients of the filter having been created using a Heyser spiral correction method to correct or improve low frequency response of the filter, the frequency response of the FIR filter being defined by a multi-dimensional polynomial at low frequencies and being calculated by conjugation to a target at high frequencies. - View Dependent Claims (15, 16, 17, 18)
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Specification