Why is the LED on my subwoofer red ?

If the LED on my subwoofer is red, this indicates that the subwoofer amplifier is going into protection mode. In most cases, this is the result of an assembly or electronic voltage malfunction. When an amplifier is electrically underpowered, it goes into protection to prevent it from going out of order. 

This problem can have several causes : 

  • The electronic power supply to the cabinet. To check this, the first step is to use a voltmeter to check the voltage at the cabinet terminals (+ and -). By switching off the ignition and stopping the engine, the voltage should be between 12.6 and 12.8 volts. If the voltage measured is significantly lower than normal, this could be due to a number of causes: a poor connection or a battery fault. In this case, check the condition of the battery and the vehicle's alternator. When the engine is running, the voltage should be between 13.8 and 14.4 volts for optimum recharging of the battery.

  • The sound signal input on the box. To check this, you need to check the connections, that no cables are pinched and that the contact is correct with the metal sheet.

  • The quality of the earth point. To check this, you need to check the quality of the contact point with the car's sheet metal. The earth wire must not be too long. The earth should be less than 70 cm from the box to the vehicle chassis. 

In the rarest cases, it may be the audio output of the car radio that is short-circuited.

If the subwoofer is used with an original car radio, do not connect the blue REM wire (which enables the subwoofer to be switched on by the car radio). There is no 12-volt remote on an original car radio that allows the REM wire to be connected. In the case of an installation of this type, you will need to activate the auto-power button on the subwoofer. 

Note that either auto-power or REM is used (with an aftermarket car radio), but never both at the same time. 

If none of these attempts is successful, never open the cabinet. This will invalidate the warranty. Contact your dealer if you have not found a solution to the problem. 

Applicable products: ISUB Active and ISUB Active 2.1 subwoofers.


Suggestion in connection with this article :

- Does my subwoofer need to be a particular shape ?


Subscribe to our newsletter and receive a preview of the latest audio innovations from Focal and Naim.