Zrad_m Zp(k0*R_m)/Sd_m "Radiation impedance of the midwoofer"
Zbv_m rho0*c0^2/(i*2*pi*freq*Vback_m) "Back volume impedance of the midwoofer"
Zrad_t Zp(k0*R_t)/Sd_t "Radiation impedance of the tweeter"
Zbv_t rho0*c0^2/(i*2*pi*freq*Vback_t) "Back volume impedance of the tweeter"