Start on one corner of the grille with the pick tool and very slowly pull the grille out. Once one corner is pulled out 1/8" - 1/4" remove the pick tool and reposition it a couple inches away from where you started, then pull the grille out another 1/4" or so. Keep repeating this process until you are at the other end of the grille and then start from the beginning pulling it a little more out each time until the grille is loose enough that you can remove it by hand.
1. If you flip the speaker over you can pull the grille out from the bottom. The advantage of doing this is that if you accidentally scratch the grille it won't be as visible since it will be on the bottom of the grille.
2. You want to apply constant force when pulling the grille out it may not seem like its budging at first but eventually it will start to move. If you try and force the grille out quickly you will damage it.
3. Do not throw away the sticky black stuff that holds the grille in. It is there to prevent vibration and hold the grille in place. If it falls out simply put it back in place.
4. Never touch the speaker cabinet with the pick tool it will leave a mark.
5. Once the grille is pulled out about 1/4" insert the pick tool in the portion of the grille that was inside of the speaker cabinet and continue pulling it out slowly. This way if you accidentally scratch the grille it will not be visible since that portion of the grille will be inside of the speaker once it is re-installed.
Most importantly take your time!!! It should take about five to ten minutes to remove the grille if you rush the process you will damage the speaker cabinet or the grille.