To be honest, I'm pretty new to Boxster's, so I am not sure. It is held in place by the 2 large plastic "bolts" into the mounting holes on the cover piece on the top of the motor... Hope that helps...
Although the speakers work fine, This was not hooked up when I bought the car. That's why I'm selling it. I've discovered you can get the wiring Harness on line... Regardless, I've lowered the price to $275 if you need the. Crutchfield has it I believe.