All the speakers I have ever heard of are more than 1 ohm. Of course somebody "could" have a built a 1 ohm for a special circumstance.......but I doubt it.
Now do people parallel speakers and get the impedance too low?
People also drive and drink.
In either case they don't know what they are doing.
Lowest impedance I have ever heard of is old Bose speakers that were 2 ohms. They may still be. Keep waiting for jaak to a sweep a septrum analyzer across one and tell us........
In any event the impedance of a non Bose auto speaker system is almost positively 4 ohms or greater, with a good liklelyhood that it is 8 ohms.