EX5 Technics Speaker problems

We have a Ex5 Technics with a blown speaker diaphram

Its a 7 inch 4 ohms

I have a slightly larger speaker [ 9 inch] that I could fit but not sure if a speaker that is 8 ohms is exceptable [ or can I connect another smaller speaker in series or is it in parallel to get the ohms down to about the 4 ohms as original.

Thanks from Dave L [in NZ.]