Based on your numbers they add 10% entropy per character. Which compounds into an increase of 210% over a length of 12 characters. Thus you'd need the password to be at least 3 times longer with only alphanumeric characters to have the same entropy.
number of characters required for 128 bit entropy password using alphanumerics: 21.49[1]. round off to 22
number of characters required for 128 bit entropy password using all printable characters: 19.5[2]. round off to 20.
22/20 = 110%
[1] https://www.wolframalpha.com/input/?i=solve+log_2(62%5Ex)%3D... (under "real solution", click on "approximate form")
[2] https://www.wolframalpha.com/input/?i=solve+log_2(94%5Ex)%3D...