What you need:
Here is the download link for Viper: http://vipersaudio.com/swupdate/viper4android/download.html
1. After you download and install the one for 4.x in the download link above, open it up and it’ll have you install the drivers. I always do super high quality. Itll download and then tell you to reboot. Reboot.
2. Go into settings > apps and disable DSP manager.
3. Download this app: http://goo.gl/YGjmb and move Viper4Android to a system app and itll make you reboot again. I know there are other ways to do this but I’m lazy and found it easy to do.
4. Now Viper is your “stock” equalizer. From here you can go into the app and make the settings whatever you want. I honestly haven’t gotten into the actual advanced settings much but here is how I have mine under headset and bluetooth:
Master Power: enabled
Forced Enable V4A: unchecked (dont mess with this, itll make you lose audio on youtube)
Playback Gain Control: Enabled
Effect Strength: Extreme
Preset: Rock (you can make this whatever you want of course but as a metal head I think rock has worked the best for the preset ones)
Headphone Surround +: Unchecked (sounds weird to me)
Effect Level: Unchanged
Viper Bass: Enabled
Bass Boost: 12.0 dB
Viper Clarity: Enabled
Auditory System Protection: Unchecked
Binaural Level: Unchanged
Common Issues: At times I have found it likes to go out and sounds like poop. A lot of times all I have to do is open the Viper app and it kicks back in for awhile without issue and others I have to enable compatible mode.As somebody said previously compatible mode can also cause issues with YouTube and other apps with its audio. This is the link for the XDA G2 Viper support thread, http://goo.gl/w26cyi. Check that out in as there are people that go 100000x more into it than I do but with just the settings I use I think it sounds good enough but that’s a good place to go and learn how it works and get some really good support for it.