This seems to be what you'd like, but I can't discover how it was achieved.
http://audioklassiks.de/wordpress/?p=2303
If you aren't comfortable soldering and opening equipment it might not be possible. Removing speakers to access the inside of a cabinet can be distressing and extreme care needs to be taken not to damage delicate cones, so I get you concern, particularly if slotted screws were used.
Having said that, it is entirely possible by encasing the screw head with your thumb and forefinger to keep the screwdriver in contact with the screw, and using a very long screwdriver, which helps keep it perfectly perpendicular. Just use as little force as is necessary to keep the screwdriver in contact with the screw and slowly rotate the screwdriver. Gently and slowly is the key, one screw at a time. If your muscles are up to it, consider taking a few goes for each screw, so there are no mishaps.
http://audioklassiks.de/wordpress/?p=2303
If you aren't comfortable soldering and opening equipment it might not be possible. Removing speakers to access the inside of a cabinet can be distressing and extreme care needs to be taken not to damage delicate cones, so I get you concern, particularly if slotted screws were used.
Having said that, it is entirely possible by encasing the screw head with your thumb and forefinger to keep the screwdriver in contact with the screw, and using a very long screwdriver, which helps keep it perfectly perpendicular. Just use as little force as is necessary to keep the screwdriver in contact with the screw and slowly rotate the screwdriver. Gently and slowly is the key, one screw at a time. If your muscles are up to it, consider taking a few goes for each screw, so there are no mishaps.