Remove all the screws on the perimeter of the speaker. Use locking pliers to remove the nuts. There are eight bolts holding the speaker in place.

Pull the old speaker off of the board and insert the new speaker the same way you removed the old one.

When tightening the nuts back down on the bolts, be sure to tighten them by alternating, working in diagonals. (i.e. once you tighten one down go diagonal from it and work on the next one.

Repeat with the other speaker if necessary.