1. The structure and characteristics of the speaker system: The speaker system is composed of a tweeter, a midrange unit, a bass unit, and a frequency divider that distributes signals.
 
2. Why protect the tweeter and midrange unit:
The tweeter and midrange unit are the most fragile and vulnerable components in the audio system. The voice coil that makes up the speaker is very thin. In the improper matching of the impedance and power of the power amplifier, as well as improper adjustment and use, it is often burnt out due to accidental or sudden large currents:

The combination of tweeter power amplifier and woofer makes the tweeter work under continuous high load.
Today's speakers are usually independently designed and sold separately, rather than matched with power amplifiers. In this way, if the selection is improper, the entire system may be damaged due to mismatching.
The bass power amplifier suffers from overcurrent impact due to overload operation caused by some reason. This problem often occurs when playing high-density optical discs with a relatively wide range of dynamic balance of musical tones.

Digital recorders, including high-density discs, have the function of resetting high-frequency materials to produce special high-frequency tones in the accent speakers;
If the potentiometer is adjusted improperly, the speaker will be damaged.

     Accidental or sudden treble will produce high current in the treble region and damage the tweeter;
     Occasional or sudden screams will produce high current in the treble region and damage the tweeter;
     Self-excited whistling caused by sudden changes in the microphone position will cause high current in the treble region to damage the tweeter;
     The drop and collision of the microphone will cause high current in the treble region to damage the tweeter;
     Plugging or unplugging the microphone or signal line with power will cause high current in the treble area and damage the tweeter;
     A sudden increase in volume will cause high current in the treble region to damage the tweeter;
     The power supply voltage is unstable or there is surge interference, which will cause high current in the treble area to damage the tweeter;

In any of the above situations, the high-midrange unit will be damaged. Once damaged, the entire audio system will be forced to stop using. Due to the large size and heavy weight, repair and maintenance are very inconvenient, so timely and effective overcurrent protection of the tweeter and the circuit must be carried out to avoid the above problems.
 

3. How to protect the high midrange unit?

1. The most commonly used one is a disposable fuse, and the protection requirements of the speaker system are relatively strict. Ordinary fuses only play a one-time protective role in the horn, which increases the repair rate of the product; In addition, additional fuse boxes and wires increase the manufacturer's cost. In addition, the fuse used must also meet the specifications, the wrong specification of the fuse will damage the speaker.
2. Installing circuit breakers is also a solution; however, they will make noise when they start to disconnect before they are disconnected.
3. Using the protection scheme of unit circuit, this scheme is very good, but it needs sampling, amplification, comparison, control and waiting for the cooperation of a series of circuits. Not only the number of components is large, the procurement cost is high, but the failure rate is high, the production debugging is difficult, and the general application is less.
4. Use a small resistance and a small bulb in parallel as a protection circuit. The circuit is simple, but the loss is large. It is generally not used except for simple audio.
The above protection methods have their own advantages and disadvantages. The best, most direct, reliable, and low-cost solution is recommended to choose "polymer PTC resettable fuse components". The resettable fuse is equivalent to a soft switch when it is disconnected (in a high-impedance state). When the fault is eliminated, it will automatically return to the state of the low resistance path.