I think I slowly eased in to it instead of it suddenly happening because I never noticed anything. Voice just got slowly deeper over time. If pubes is a good indication I got those by about eight, but I'm a very hairy man.
Weirdest thing though, at one point in 7th grade my voice got massively deep for two whole weeks. Like, radio worthy. Everyone was all over my ass cause it was so cool. I woke up one day and it was even higher than it was before. forget me, I want it back. I have no idea what happened and I can't explain it at all.