Impedance
The electrical resistance of a subwoofer when a signal is applied to it. This parameter is important primarily for selecting a subwoofer-amplifier pair: at a lower impedance than that of the amplifier, the subwoofer will distort the sound, at a higher impedance the sound will be too quiet.
For dual voice coil models (see above), the impedance is specified for one of the voice coils.
Resonant frequency
The natural frequency of the cone in the subwoofer speaker, namely the frequency with which the cone will oscillate if the speaker is suspended freely in the air and a single impulse is transmitted to the cone (for example, by clicking on it with your finger). In subwoofers, this parameter determines, in particular, the lower limit of the frequency range (see above): at frequencies below the resonant sound power drops sharply. Accordingly, for deep rich bass, the resonant frequency should be as low as possible. This parameter is also used to calculate the size of the enclosure for the subwoofer.
