Thanks, THIS is cool, just did it on my FL A3 Sportback, MIB2 Harman MHI2 with Audi Sound System.
I first edited the 00x003B00 with subwoofer dial range set to min= F7 , center= 00, max= 09.
Calculeted the checksum and a restart of the radio, and there the sub dial was in the sound menu, great...