Stan Warren is a big believer in freezing. He told me we can all do it at home with some Dry Ice even though Dry Ice is not as cold as Cryo. He did a test with some friends at a local university near him (Oregon) who had a cryo chamber to freeze the cables. Some cables were Cryogenically frozen; some frozen in Dry Ice and some not frozen. In listening tests it was easy to figure out the cables that were not frozen at all. They could not tell any difference between the cables that were Cryo and the ones frozen in Dry Ice. So the conclusion was that Dry Ice is cold enough; the extra coldness of Cryogenic freezing is not necessary.
I believe Dry Ice is about minus 100 degrees fairenheit. Stan controls the freezing and thawing by using his home freezer as a intermediate step between room temperature both ways. Your home freezer will easily go to zero and probably colder if you turn it up some.