How could two circles be connected when one has an interrupted edge ring? I created a membrane of one speaker and want to connect a duplicate, the outer edge ring is interrupted (because I used Knife Project to cut the holes in the case). The problem is that Grid Fill expects a closed loop and Bridge Edge Loops creates this: 



Is there another way than connecting them manually?

.blend
This is actually because you have a mis-matched vertex count, most likely because of a mirroring error:



You also seem to have a duplicate of the speaker:



To fix this:




Select a vertex on the speaker and press CtrlL to select connected geometry, then press Delete> vertices to delete it.
Select the extra loops on the sides and delete them with Delete > Edge loops
Bridge edge loops now works as expected.