Here the radio is removed using two release brackets (1 and 2). The release brackets press on the radio's mounting springs and fit into the slots, which causes the radio to be removed from the mounting hole.
To access the fastening screw (2) of the high frequency speaker (1), the door trim must be removed.
Dismantling the radio receiver
The Audi A4 uses a new generation of wide-body radios. In our descriptions we refer to factory installation, this also applies to the speaker installation locations.
1. Make sure you have the code number for the installation against unauthorized dismantling.
2. The radio receiver must be turned off.
3. Insert the release brackets (sometimes included in the radio mounting kit) into both slots at the bottom of the front decorative panel and remove from the grooves.
4. Remove the radio from the center console.
5. In extreme cases, unlocking is possible using two template plates about 1 mm thick. In this case, you need to carefully grasp the radio receiver in the cassette holes and remove it from the center console.
6. Disconnect the power and antenna connectors.
7. When installing, make sure that the mounting pin on the back of the radio fits into the hole provided for it in the dashboard. To do this, hold the radio absolutely horizontally.
8. Now press the radio slightly into the mounting hole so that the mounting springs enter the grooves.
9. Enter the code against unauthorized dismantling according to the operating instructions.
Read the original source on the website audimanual