Wide-band equalization system

1. A method for equalizing an audio system using near- and far-field measurement data, the method comprising:

capturing a set of room impulse responses (“RIRs”) at a plurality of listening locations of the audio system;

determining low-frequency finite impulse response (“FIR”) coefficients for a low-frequency FIR filter;

determining mid-frequency FIR coefficients for a mid-frequency FIR filter;

determining high-frequency FIR coefficients for a high-frequency FIR filter;

generating the low-frequency FIR filter utilizing the low-frequency FIR coefficients;

generating the mid-frequency FIR filter utilizing the mid-frequency FIR coefficients;

generating the high-frequency FIR filter utilizing the high-frequency FIR coefficients;

generating an at least one low-frequency filter of the audio system utilizing a subwoofer equalizer (“EQ”) that includes the low-frequency FIR filter;

generating an at least one mid-frequency filter of the audio system as a plurality of cascaded infinite impulse response (“IIR”) filters that are derived from the mid-frequency FIR filter; and

generating an at least one high-frequency filter of the audio system as a plurality of cascaded IIR filters that are derived from the high-frequency FIR filter.

2. The method of claim 1 , wherein the subwoofer EQ further includes a decimator filter and an interpolator filter.

3. The method of claim 1 , wherein generating the low-frequency FIR filter includes:

determining a low-frequency inverse spectrum from the captured set of RIRs; and

multiplying the captured low-frequency inverse spectrum by a target function that results in an EQ filter frequency response.

4. The method of claim 3 , wherein the target function is a bandpass filter with 4 th order low-pass and high-pass Butterworth filter characteristics.

5. The method of claim 3 , wherein determining the low-frequency inverse spectrum further includes smoothing peaks of the EQ filter frequency response utilizing a smoothing factor.

6. The method of claim 1 , wherein generating the high-frequency FIR filter coefficients includes:

multiplying a near-field RIR derived from the captured set of RIRs by a first time window;

determining the magnitude spectrum of the windowed near-field RIR;

smoothing the magnitude spectrum with a first smoothing factor;

determining a log-magnitude inverse spectrum of the smoothed magnitude spectrum;

smoothing the peaks of the log-magnitude inverse spectrum with a second smoothing factor to derive a high-frequency EQ filter spectrum;

scaling the high-frequency EQ filter spectrum to a gain equal to zero decibels at an operating frequency fg;

limiting the response of the high-frequency EQ filter spectrum to an upper operating frequency fgu;

clipping the gain of the high-frequency EQ filter spectrum to a maximum allowed gain;

determining an EQ FIR filter impulse response out of the log-magnitude inverse spectrum; and

applying a second time window to the EQ FIR filter impulse response.

7. The method of claim 6 , wherein determining the EQ FIR filter impulse response out of the log-magnitude inverse spectrum is implemented utilizing a Hilbert transform.

8. The method of claim 6 , wherein the second smoothing factor is greater than the first smoothing factor.

9. The method of claim 1 , wherein generating the mid-frequency FIR filter includes:

multiplying a far-field RIR derived from the set of captured RIRs by a first time window;

determining a magnitude spectrum of the windowed RIR utilizing an N-point fast Fourier transform (“FFT”);

smoothing the magnitude spectrum with a first smoothing factor;

determining a log-magnitude inverse spectrum of the smoothed magnitude spectrum; and

determining an EQ filter frequency response out of the log-magnitude inverse spectrum utilizing a target function.

10. The method of claim 1 , wherein the equalization of the low-frequency signals, the mid-frequency signals, and the high-frequency signals is performed simultaneously.

11. A Wide-band Equalization System (“WBES”) for equalizing an audio system using near- and far-field measurement data, the WBES comprising:

a bass manager in signal communication with a signal source;

a subwoofer EQ in signal communication with the bass manager, and configured to receive low-frequency signals from the bass manager; and

a plurality of satellite channels in signal communication with the bass manager, and configured to receive mid- and high-frequency signals from the bass manager.

12. The WBES of claim 11 , wherein the subwoofer EQ includes a decimator filter, the at least one low-frequency FIR filter, and an interpolator filter.

13. The WBES of claim 11 , wherein each of the plurality of satellite channels includes an at least one mid-frequency IIR filter and an at least one high-frequency IIR filter, where the at least one mid-frequency IIR filter and the at least one high-frequency IIR filter are generated from the at least one mid-frequency FIR filter and the at least one high-frequency FIR filter, respectively.

14. The WBES of claim 13 , further including a plurality of cascaded IIR filters that are generated from the at least one mid-frequency FIR filter and the at least one high-frequency FIR filter, respectively.

15. A Wide-band Equalization System (“WBES”) for equalizing an audio system using near- and far-field measurement data, the WBES comprising:

means for capturing a set of room impulse responses (“RIRs”) at a plurality of listening locations of the audio system;

means for determining low-frequency finite impulse response (“FIR”) coefficients for a low-frequency FIR filter;

means for determining mid-frequency FIR coefficients for a mid-frequency FIR filter;

means for determining high-frequency FIR coefficients for a high-frequency FIR filter;

means for generating the low-frequency FIR filter utilizing the low-frequency FIR coefficients;

means for generating the mid-frequency FIR filter utilizing the mid-frequency FIR coefficients;

means for generating the high-frequency FIR filter utilizing the high-frequency FIR coefficients;

means for generating an at least one low-frequency filter of the audio system utilizing a subwoofer equalizer (“EQ”) that includes the low-frequency FIR filter;

means for generating an at least one mid-frequency filter of the audio system as a plurality of cascaded infinite impulse response (“IIR”) filters that are derived from the mid-frequency FIR filter; and

means for generating an at least one high-frequency filter of the audio system as a plurality of cascaded IIR filters that are derived from the high-frequency FIR filter.

16. The WBES of claim 15 , wherein the means for generating the low-frequency FIR filter includes:

means for determining a low-frequency inverse spectrum from the captured set of RIRs;

means for multiplying the captured low-frequency inverse spectrum by a target function that results in an EQ filter frequency response.

17. The WBES of claim 16 , wherein the means for determining the low-frequency inverse spectrum further includes means for smoothing peaks of the EQ filter frequency response utilizing a smoothing factor.

18. The WBES of claim 15 , wherein the means for generating the high-frequency FIR filter coefficients includes:

means for multiplying a near-field RIR derived from the captured set of RIRs by a first time window;

means for determining the magnitude spectrum of the windowed near-field RIR;

means for smoothing the magnitude spectrum with a first smoothing factor;

means for determining a log-magnitude inverse spectrum of the smoothed magnitude spectrum;

means for smoothing the peaks of the log-magnitude inverse spectrum with a second smoothing factor to derive a high-frequency EQ filter spectrum;

means for scaling the high-frequency EQ filter spectrum to a gain equal to zero decibels at an operating frequency fg;

means for limiting the response of the high-frequency EQ filter spectrum to an upper operating frequency fgu;

means for clipping the gain of the high-frequency EQ filter spectrum to a maximum allowed gain;

means for determining an EQ FIR filter impulse response out of the log-magnitude inverse spectrum; and

means for applying a second time window to the EQ FIR filter impulse response.

19. The WBES of claim 15 , wherein the means for generating the mid-frequency FIR filter includes:

means for multiplying a far-field RIR derived from the set of captured RIRs by a first time window;

means for determining a magnitude spectrum of the windowed RIR utilizing an N-point fast Fourier transform (“FFT”);

means for smoothing the magnitude spectrum with a first smoothing factor;

means for determining a log-magnitude inverse spectrum of the smoothed magnitude spectrum; and

means for determining an EQ filter frequency response out of the log-magnitude inverse spectrum utilizing a target function.

20. The WBES of claim 15 , wherein the means for determining the low-frequency, the mid-frequency, and the high-frequency FIR coefficients includes a digital signal processor (“DSP”).

21. The WBES of claim 15 , wherein the means for generating the at least one low-frequency filter of the audio system includes a DSP.

22. The WBES of claim 11 , wherein the means for generating the at least one mid-frequency filter of the audio system includes a DSP.

23. The WBES of claim 11 , wherein the means for generating the at least one high-frequency filter of the audio system includes a DSP.