It's called a surround. A gasket may also be in use, though. But sounds like your driver simply needs the surround replaced altho when you pull the driver out of the mounting you might be prepared to replace the gasket (between driver and baffle) as well, something like door/window weatherstripping can work well enough. Might want to look at some instructional videos on the subject before starting, but it's not all that hard. Good luck and stay safe!