When repairing speakers, gaskets can and should be reused as often as possible. Gaskets vary slightly in a lot of cases, and many are no longer made, or are unavailable. The best way to insure a correct fit is to carefully remove the original gaskets for reuse. If the gaskets are not reusable for whatever reason, donít worry! This is generally not a big deal, as in most cases they are not a critical part.
Gaskets which are mounted to the front of drivers, over the outside edge of the surround, are only necessary if the driver is going to be installed so that the gasket is the sealing surface. An example of this would be in cases where you are installing the driver inside a speaker cabinet. Alternatively, in most finished speakers, the gaskets are exposed on the front of the driver, and do not create a seal. Although exposed gaskets may not serve a physical function, they may be aesthetically pleasing, and act more like a trim ring than a gasket.
There are three primary reasons gaskets are installed on the speaker drivers when they are factory built. Firstly, the gasket allows the manufacturer the ability to mount the driver inside a speaker cabinet if that is the design. Secondly, gaskets can help protect the drivers during shipping by keeping the surrounds from rubbing against the shipping container. And finally, (as previously mentioned) gaskets may be seen as aesthetically pleasing.