Max. power
The maximum signal power that the subwoofer is able to withstand for a short time (up to several seconds) without any negative consequences. When selecting an amplifier-subwoofer pair, it is recommended to take a subwoofer with a maximum power of at least twice the maximum power of the amplifier. In general, the higher the maximum power, the more resistant the subwoofer is to overloads.
Frequency range
The range of audio frequencies reproduced by the subwoofer. It is believed that the human ear is capable of perceiving a frequency range of the order of 16 – 20,000 Hz, but in this case note that the subwoofer is designed to reproduce the lower frequency band (up to 200 Hz). Accordingly, in the case of the lower limit of the range, everything is simple: “the lower, the better”; the upper one should not be lower than the lower limit of the main car audio — otherwise there will be "gaps" in the frequencies, which will affect the sound quality.
Sensitivity
Sensitivity determines the loudness of the subwoofer when a signal of a certain power is connected to it: with equal signal power and impedance (see below), the subwoofer with the higher sensitivity will sound louder.
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.
Subsonic filter
The presence in the subwoofer
of an infra-low frequency filter (Finch), also referred to as Subsonic. This filter "cuts" subsonic frequencies, preventing the subwoofer from reproducing them. Often this filter has a frequency control. This feature serves several purposes. Firstly, the human ear is no longer able to recognize such vibrations, and there is no point in reproducing them — this only leads to useless expenditure of energy. Secondly, intense infrasound can adversely affect well-being (both physical and mental). Thirdly, working with infra-low frequencies at high power can damage the subwoofer itself: figuratively speaking, the coil “blows” off the speaker.
