the folder vo goes in Steam\steamapps\common\dota 2 beta\dota\sound
the folder voscripts goes in Steam\steamapps\common\dota 2 beta\dota\scripts
-=YOU MUST LAUNCH THE GAME WITH SPECIAL LAUNCH OPTIONS=-
Under general > set launch options, add -override_vpk
This only replaces the default announcer lines. Equiping any sort of announcer in-game will override the mod as it would the normal announcer.
If you somehow manage to royally fuck up or this doesn't work, verify your game cache. This will uninstall any modified files and fix everything.
ALL SOUNDS ARE RIPPED FROM HALF-LIFE WITH EXTREME PREJIDUCE