Loudspeaker protection

https://www.eeweb.com/soft-start-for-loudspeaker-with-dc-protection/

The protection of loudspeakers occurs after a power amplifier gets damaged. During this time, there might be some DC voltages floating inside the circuit and on the output of amplifier that would create more damage and thus, affecting the loudspeaker. Since the amplifiers are connected to the loudspeaker, the 12 V relay RL1 cuts the line of connection when it gets triggered. This interrupts the operation immediately while stopping the DC voltage to reach the loudspeaker. The relay is connected in parallel to provide 3 seconds of delay time from the instance when the power supply is applied. The delay is essential to the circuit as it protects the loudspeaker from sudden voltage transients or undesirable explosion when switch of the supply has been opened.

The operation of the circuit is indicated by the visual light from LEDS D4-5 where D4 signifies the green for OK status while D5 signifies the red for the delay timing or DC voltage presence. The circuit is being supplied symmetrically by 12 V, which can be sourced from a small independent power supply or from a reduced voltage from mains power supply. The circuit is best constructed for protection for each final amplifier that will be arranged. The quality of the relay contacts should be adequately proportional in terms of the large current that would pass the circuit during the