[python] Add speaker module

src/python/speaker/alignment.py

@@ -0,0 +1,33 @@
+import numpy as np
+
+
+def main():
+    c = 343
+
+    tweeter = np.array([0, 0, 1.2])
+    midrange = np.array([0, 0, 1.1])
+    woofer = np.array([0, 0, 0.9])
+    subwoofer = np.array([0, 0, 0.5])
+
+    listener = np.array([1.0, 2.0, 1.2])
+
+    t_tweeter = np.linalg.norm(listener - tweeter)/c
+    t_midrange = np.linalg.norm(listener - midrange)/c
+    t_woofer = np.linalg.norm(listener - woofer)/c
+    t_subwoofer = np.linalg.norm(listener - subwoofer)/c
+
+    rd_midrange = t_midrange-t_tweeter
+    rd_woofer = t_woofer-t_tweeter
+    rd_subwoofer = t_subwoofer-t_tweeter
+
+    print(f"t_tweeter={t_tweeter*1000:.2f} ms")
+    print(f"t_midrange={t_midrange*1000:.2f} ms")
+    print(f"t_woofer={t_woofer*1000:.2f} ms")
+    print(f"t_subwoofer={t_subwoofer*1000:.2f} ms")
+    print(f"rd_midrange={rd_midrange*1000:.3f} ms")
+    print(f"rd_woofer={rd_woofer*1000:.3f} ms")
+    print(f"rd_subwoofer={rd_subwoofer*1000:.3f} ms")
+
+
+if __name__ == "__main__":
+    main()

src/python/speaker/crossover.py

@@ -0,0 +1,42 @@
+import matplotlib.pyplot as plt
+import numpy as np
+from scipy.signal import butter, filtfilt, firwin, lfilter
+
+
+def main():
+    fc = 400
+    fs = 48000
+    dt = 1/fs
+    n = fs
+
+    sig = np.zeros(n, dtype=np.float64)
+    sig[0] = 1.0
+
+    num_taps = 101
+    lowpass_taps = firwin(num_taps, fc, window='hamming', fs=fs)
+
+    # Design a highpass FIR filter by spectral inversion
+    highpass_taps = -lowpass_taps
+    highpass_taps[num_taps // 2] += 1
+
+    lowpass_sig = lfilter(lowpass_taps, 1.0, sig)
+    highpass_sig = lfilter(highpass_taps, 1.0, sig)
+
+    freqs = np.fft.rfftfreq(n, d=dt)
+    lowpass_spectrum = np.fft.rfft(lowpass_sig)
+    highpass_spectrum = np.fft.rfft(highpass_sig)
+
+    lowpass_amplitude = np.abs(lowpass_spectrum)
+    highpass_amplitude = np.abs(highpass_spectrum)
+    mix_amplitude = lowpass_amplitude+highpass_amplitude
+
+    # plt.semilogx(freqs, 20*np.log10(lowpass_amplitude), label="LP")
+    # plt.semilogx(freqs, 20*np.log10(highpass_amplitude), label="HP")
+    plt.semilogx(freqs, 20*np.log10(mix_amplitude), label="LP+HP")
+    plt.grid()
+    plt.legend()
+    plt.show()
+
+
+if __name__ == "__main__":
+    main()

src/python/speaker/enclosure.py

@@ -0,0 +1,63 @@
+
+def sealed_enclosure_volume(Vas, Qtc, Qts):
+    """
+    Vas: Equivalent compliance volume
+    Qtc: Desired system Q, typically around 0.7 for a good balance between transient response and efficiency
+    Qts: Total Q factor of the driver
+    """
+    return Vas/((Qtc/Qts)**2-1)
+
+
+def ported_enclosure_volume(Vas, Fs, Fb):
+    """
+    Vas: Equivalent compliance volume
+    Fs: Driver resonant frequency
+    Fb: Tuning frequency
+    """
+    return (Vas*(0.7*Fs))/(Fb-0.7*Fs)
+
+
+def port_length(Vb, Fb, D):
+    """
+    Port length for a ported speaker enclosure
+
+    Vb: Enclosure volume
+    Fb: Tuning frequency
+    D: Port diameter
+    """
+    return (23562.5*(D**2))/((Fb**2) * Vb)
+
+
+def main():
+    Vas = 50
+    Qtc = 0.707
+    Qts = 0.4
+    Fs = 30
+    Fb = 35
+    D = 10
+
+    Vas = 197
+    Qtc = 0.707
+    Qts = 0.32
+    Fs = 17
+    Fb = 25
+    D = 12
+
+    Vas = 103.61
+    Qtc = 0.707
+    Qts = 0.35
+    Fs = 28
+    Fb = 32
+    D = 10
+
+    Vs = sealed_enclosure_volume(Vas, Qtc, Qts)
+    Vp = ported_enclosure_volume(Vas, Fs, Fb)
+    Lp = port_length(Vp, Fb, D)
+
+    print(f"sealed: {Vs:.2f} l")
+    print(f"ported: {Vp:.2f} l")
+    print(f"port:   {Lp:.2f} cm")
+
+
+if __name__ == "__main__":
+    main()