'89 Accord grills have bolts built into them that go through holes in the rear deck/shelf and are secured with nuts. You'll have to remove the nuts from inside the trunk to be able to remove the grills. Once removed you'll find that the speakers mount inside the grills. turn them over and use a Phillips head screw driver to remove the screws so you can remove the grill cover from the base.

Or at least that's what it was like in an '87 Accord I had years ago.

JD