As a typical speaker, you can clearly see the physics of film motion, especially the downward direction. The audio signal shall not be too strong, otherwise it will cause the vibration element to contact with the fixed frame assembly, or cause the suspension material (annular ring or elastic frame) to be excessively tensioned. In addition, the root-mean-square value of the audio signal cannot be too large, otherwise the voice coil will overheat. The overheating of the voice coil will deform the circle of the spool, causing friction with the edge of the magnet or pole piece. Moreover, the high temperature in the voice coil will also lead to its poor electrical insulation performance, and the turn of the voice coil will be short-circuited, thus reducing the impedance of the voice coil and overloading the amplifier. Too high voice coil temperature will also heat the permanent magnet and may cause demagnetization.
Technologies used to prevent speaker horn damage include automatic gain control (AGC) for input signal amplitude and/or power supply voltage, dynamic range compression (as described above), hard limiting, soft limiting, and overcurrent measurement of amplifier output. The disadvantage of these technologies is that they are all feed-forward and cannot sense the actual PA Loudspeaker taper, voice coil temperature, or horn loudspeaker impedance (which changes proportionally with temperature). It is expected to realize more complex protection mechanisms such as thermal feedback in the future, but the current conventional method is one or more of the above protection mechanisms.
