Removing the back panel will allow you to access the speaker and main amplifier chassis

Make sure that the amplifier is unplugged before starting disassembly

Identify and remove the screws holding on the back panel. On my particular Ibanez, 6 Philips head screws are used

Usually, guitar amplifiers will have a back panel that covers only around half of the amplifier cabinet, while bass amplifiers will have a back panel that seals the cabinet completely