The Chinese downloader component is experiencing issues, please avoid trying to change to Chinese till a fix is done.
LVOC - LoL VO Changer

Current version for Windows: v3.0.4

Current version for Mac OSX: v3.0.4

[In the process of making updated tutorials]
This application allows you to change the language of the in-game and champ select audio for League of Legends to any of your choosing (Japanese, Korean, Spanish, Turkish, etc.) provided that the language is supported by Riot.

By downloading and/or using this application, you acknowledge and agree to abide by the terms.
NOTE: as with any other method of tampering with the game files, this can potentially break your game/launcher. USE AT YOUR OWN RISK

IMPORTANT: IF YOU INSTALLED VO SKINS WITH WOOXY BEFORE, MAKE SURE YOU UNINSTALL THEM BEFORE USING LVOC. Not doing so may result in issues.
Downloads
Recent changes:

v3.0.4 (29th April, 2017)
  • Fixed an issue which prevented VO changes for users of the EU English client.
v3.0.3 (28th April, 2017)
  • League Client Update support! LVOC no longer relies on the League Client/Patcher to obtain the VO files, instead LVOC now has its own internal downloader specifically for VO files. Note: The files are still coming directly from Riot's servers/network, with the exception of the Chinese ones which are still hosted on Google Drive.
  • LVOC no longer automatically closes your League processes before changing the VO, since I thought it'd be strange behavior with this new update. I'd still advise making sure League is closed though.
  • Fixed an issue that caused the elements in the UI to become messed up if you set an incorrect LoL path then tried to change the voices.
  • Fixed an issue with the "Change champions" setting. Previously, it may or may not actually save the setting when you restarted the program.
  • Fixed an issue where the "update is available" notification would keep showing up even though there wasn't actually an update available.
v3.0.1 (14th March, 2016)
  • Fixed a small issue with the "Set all to" button under "Select champions"
v3.0.0 (13th March, 2016)
  • Custom announcer installation now available. Please note that if you want to use a custom announcer pack (like Sneaky & Meteos) WITH a different language for champion VO, install the different language VO first, then install the custom announcer.
  • Added button to change all champ language under "Settings" with one click, for convenience.
  • LVOC now saves your Champion configurations when you click change, so you don't have to set, for example, Yasuo to Korean and Ahri to Japanese every time you use the app.
  • LVOC now has a built in self-updater on Windows.
  • I changed how I packaged the application to see if it will help with the 0x0000018 error. You'll see more files than "LVOC.exe" when you unzip the .zip file, but you can ignore those extra files.
v3_beta_patch6 (20th February, 2016)
  • Quick fix for the missing announcer vo on garena............
v3_beta_patch5 (16th February, 2016)
  • Quick fix for the stuck on "Extracting VO" problem for Garena
v3_beta_patch4 (13th February, 2016)
  • Fixed the "unable to transfer champ select from ja_JP to en_AU" error
  • Fixed an issue for Oceania where it'd get stuck on "looking for announcer files"
  • Fixed the crashing issue that happened upon VO download completion for Oceania and Garena, for users working with around 4GB memory and 32 bit Windows.
  • There is an issue where Mac users can't select their League app if it's not in the Applications directory, I haven't found a solution to this, so for now I recommend you guys move League of Legends to "Applications" if it's not there already.
  • LVOC will now clean up temporary VO files that were extracted during the VO change procedure upon exiting
  • Users can now generate a log file during the VO change procedure
  • "Errors encountered" shows something other than 0 now if something actually goes wrong.
v3_beta_patch3 (31st January, 2016)
  • Fixed silent champs bug on Oceania and Latin America
v3_beta_patch2 (30th January, 2016)
  • Fixed the "unable to determine locale" bug when you don't leave the locale selection on "Detect automatically"
  • Fixed the Chinese downloader
  • Fixed a an issue with Garena when installing japanese VO
  • Users should see a red error message if a VO pack didn't download properly (if this happens to you, I advise restarting the app then revert changes immediately after it finishes trying to install the VO)
  • In the "Help"->"How do I contact you about a bug?" menu, you can now generate a log file to e-mail to me (make sure you generate this immediately after you encounter a problem! Don't restart the app if you encounter a problem, unless its frozen forever)
  • In the "Help" menu, a button was added to clear all of LVOC's data. I recommend you use this upon downloading the new version. (REVERT FIRST THOUGH!)
  • Fixed the Wukong bug
  • Fixed the "Error validating LoL path" issue that happened right after the first time the user uses the application
  • Put in a temporary fix for Oceania client
v3.0.0_beta (29th January, 2016)
  • Japanese VO supported! (Note for Garena users: make sure you select "Garena" as your locale! It won't work if you leave it on "Detect automatically")
  • You don't need Java anymore. LVOC has been completely re-written, allowing it to be easier to maintain for me, and more reliable for you.
  • Missing taunts/other VO problem is now fixed.
  • Added "select/un-select" toggle for champions. For those who only wanted to change a few champions but didn't want to un-check a bunch of them one by one.
  • Added ability to install third-party Announcer packs (like the Rick & Morty one). This feature is disabled in version 3.0.0_beta, but will be available when the stable version (3.0.0) is released.
  • I probably forgot to list other stuff here but ill remember later maybe


v2.0.2 (26th July, 2015)
  • Fixed a bug where LVOC wasn't changing the Announcer audio again. This shouldn't happen again unless Riot makes a significant change to the format of the files.
  • Added the ability to change each champion's language individually. For example, Ahri to Korean, Yasuo to Chinese, Fiora to French, etc. You can find this setting by going to the "Settings" tab and clicking "Select Champions". (Note: Announcer language will still be whatever you selected as the main language to change to).
  • Temporarily disabled Advanced Mode, as it's no longer useful in its current state and seemed to cause more problems than it solved. It'll be re-implemented once it's improved.


v2.0.1 (15th June, 2015)
  • Fixed a bug where LVOC wouldn't change newer audio files (mostly the announcer). For those who are familiar, this is the bug that started happening a couple days ago.
  • Optimized the error report feature, so that it sends much faster.
  • LVOC will no longer bother trying to change the announcer audio if you selected Chinese (the Chinese announcer literally only has like 3 lines of VO for the start of the game, the rest of it is english).


v2.0.0 (2nd May, 2015)
  • Chinese VO now supported! Just select Chinese from the list of languages to change to. (See the "Help" tab in the app if you're wondering why kill callouts aren't in Chinese)
  • Support for Mac OS X! (Despite all my testing, I expect this to be somewhat buggy, so feedback is welcomed)
  • Added ability to select which champions' VO should be changed and which champions should be excluded
  • Updated interface, nothing big though (functionality is now grouped by tabs at the top of the window)
  • Added Brazil to the list of regions
  • LVOC will now automatically attempt to get the most up-to-date list of champions when you run it. This means that there will no longer be a need to update the app when a new champion releases.
  • A couple bug fixes


v1.9.8 (17th January, 2015)
  • Fix for Patch 5.1
  • Fix for "invalid LoL folder" messages for GarenaPH (Feedback on this change would be appreciated)


v1.9.7 (16th December, 2014)
  • Application will now automatically undo any previous VO changes before changing. This is to help avoid inconsistent VO files and useless back-up files. This also helps to avoid future patch issues with Garena. (Note: If you have used LVOC before, this change is most effective on a fresh install or a recently repaired client)
  • [Garena] If a user selects an incorrect League of Legends path, the error message now gives a clearer description of what path is expected.
  • [Garena] For clients installed in the default directory under Program Files, the "GarenaLoL","GameData" and "Apps" folders are all now valid paths.


v1.9.6 (11th December, 2014)
  • Fix for Patch 4.21 (yay!)
  • Garena users will no longer have to re-download the VO files if the ones they have already downloaded are up-to-date
  • New language available: Czech
  • Support for Rek'Sai!


v1.9.5 (19th November, 2014)
  • Update for Kalista


v1.9.4 (10th October, 2014) - tl;dr: lots of fixes for Garena support
  • Fixed a bug where Garena users were unable to change Announcer and Champion audio individually
  • Fixed a bug for Garena users who were using 32-bit operating systems
  • Fixed a bug for Garena users where certain folders with spaces in their names caused "Extraction failed!" messages
  • Fixed automatic error detection for Garena
  • Added undo feature for Garena client
  • Champ select audio is now changed for the Garena client