Nope, it won`t fit into that hole. The hole will be too large to have the clamps work.
Take a look at the 8″ size to fit the hole. You still may have to trim out a bit and that`s cheaper and easier than the patching of drywall. This is a good one in that size.
I`d like to install the MASIC6C 6.5″ ceiling speaker into an existing 8 3/8″ hole. Will this speakers support clips enable me to use my existing opening without having to add a patch to the ceiling? Also, please tell me the overall depth of the speaker.