With a plastic opening tool, pry along the top edge of the plastic casing.

Prying will be difficult considering the liberal amount of adhesive used to keep the casing in place. Don't give up.

Inside the casing is a small rectangular silver component. This is the speaker.

Pay attention to the orientation of the speaker.

Using pliers and enough force, pull the speaker upward and out of the casing. Once again adhesive may prove difficult.