Car speaker impedance refers to the ratio of the voltage to the current of the car speaker input signal, and its unit is ohms (Ω). In layman's terms, impedance is the resistance presented by the car speaker to the current. Impedance is not equal to resistance, but includes resistance and reactance, that is, including resistance and inductance, inductive reactance and capacitive reactance generated by capacitors. The sum of the three over a vector.
Under the same voltage, the higher the impedance, the smaller the current, and the lower the impedance, the larger the current. In the case of the same power amplifier and output power, a low-impedance car speaker can obtain greater output power, but if the impedance is too low, it will cause under-damping and bass degradation. In general, the lower the impedance of a car speaker, the harder it is to push. Impedance is not a constant value, but fluctuates continuously with the frequency of the music being played. It may be as high as ten ohms or twenty ohms at a certain frequency, or it may be as low as one ohm or below at a certain frequency. Its nominal value is the lowest impedance value presented between the resonance peaks at its resonant frequency. At present, the impedance of most car speakers is 2-8 ohms. The preferred values of speaker impedance specified by my country's national standards are 4Ω, 8Ω, and 16Ω (the recommended value of international standards is 8Ω).