It's probably 4x16 ohms. Like others have said, it can't be done with simple re-wiring.
Here are the possible permutations of four 16-ohm speakers, ABCD. Let s:series and p

arallel:
ApBpCpD = 4 ohms
Ap(BsCsD) = 12 ohms
(AsB)p(CsD) = 16 ohms
(ApB)s(CpD) = 16 ohms
As(BpCpD) = 21.33 ohms
AsBsCsD = 64 ohms