Since my amplifier dates back to the early 2000's, the soft front with the AER logo came off easily, providing access to the grille. It was not glued or otherwise attached.

To take off the grille, you need to unscrew the four screws in the four corners with your Philips screwdriver.

This is how the amp looks like once once the Grille has been unscrewed and taken off.

Please note that the speaker is very fragile, in particular since the tweeter is built in its center, so please be very carefully handling it going forward!

Note: In my version of the amplifier, there is a bass reflex pipe on the right and a hole without such a pipe on the left.

You can probably also see the handle is also taken out on the left side of the chamber.