Not 100% certain, mine are electric - just unplug
Seriously, from changing my son's broken mirror, it is done from behind the trim. The knob is attached with a split claw type fitting- designed to go together and not come apart! I had the luxury of the replacement mirror with entire cable attached to work out what / where to lever out of the car & a spare should I **** it up. It is fiddly, releasing the claw also releases balls & springs from inside the adjuster mechanism, which you will need to put back in place. Once the knob is released, it comes off into the car and the entire adjuster cable withdraws into the door. With some asistance to hold the door card, you should be able to change speakers without fully removing the card, leaving the mirror cable attached. whatever you do don't let the plastic door card rest on the ground. It is verry soft & slightest movement will put deep scratches in it probably on the inside facing i.e. visible surfaces.