To calculate the power response of a sealed
enclosure system, you will need to know the following: Vas = equivalent air compliance (litres)
Qes = electrical Q of driver at resonance
Fs = resonance frequency of driver (Hz)
PEmax = maximum input power for driver (W)
Fb = resonance frequency of the system (Hz)
Qtc = final Q of the system at resonance
Dia = effective diameter (cone + 1/3 surround) (cm)
Xmax = peak linear displacement of cone (mm)
then,
Sd = pi*(Dia/100)^2/4
Vd = Sd*Xmax/1000
n0 = 9.64*10^(-10)*Fs^3*Vas/Qes
SPL = 112 + 10*LOG(n0)
K1 = (4*pi^3*Ro/c)*Fb^4*Vd^2
K2 = 112+10*LOG(K1)
Amax = Qtc^2/(Qtc^2-0.25)^0.5 for Qtc >(1/2)^0.5,
1 otherwise
Par = K1/Amax^2
Per = Par/n0
PeakSPL = SPL+10*LOG(PEmax)
where,
pi = 3.14159265359
c = speed of sound in air (345 m/s)
Ro = density of air (1.18 kg/m^3)
n0 = free-air efficiency
SPL = driver output @1W/1M
Par = maximum linear power output
Per = electrical input required to produce Par
PeakSPL = Thermally-limited SPL in passband
At frequency F,
Fr = (F/Fb)^2
dBmag = 10*LOG(Fr^2/((Fr-1)^2+Fr/Qtc^2))
SPLd = K2+40*log(F/Fb)
Pmax = K1*((Fr-1)^2+Fr/Qtc^2)/n0
SPLt = dBmag+peakSPL
where
SPLd = displacement-limited SPL at F (dB)
Pmax = power required to produce SPLd at F (W)
SPLt = thermally-limited SPL at F (dB) |