THIS TWEAK IS OBSOLETE! If you want a system-wide equalizer, try EQE. It is much better than this.
Compatible with iOS 7, 8 and 9
Partially compatible with iOS 10 (no Control Center integration, only in Settings)
Incompatible with iOS 11. If you want a system-wide equalizer on iOS 11, wait for the EQE update.
NOTE: On some devices, the equalizer will stop applying after a certain amount of time (typically a few days). To fix this, open MobileTerminal and run the command "killall mediaserverd".
This tweak will make your audio sound better to suit your speakers/headphones. Change the sliders to modify bass, treble or mids.
It applies the equalization to your speaker output via Core Audio. So it works with every app.
It works with every type of Apple supported audio output (i.e. the earpiece, earbuds, AUX, bluetooth, dock speakers, and AirPlay).
It includes a preamp and it has 10 frequency bands: 60, 170, 310, 600, 1K, 3K, 6K, 12K, 14K and 16K Hz. It ranges from -12 to +12 dB.
You can also save and set presets if you have multiple types of speakers/headphones.
It is also availble in settings if you don't like it in the Control Center.
See larger Screenshots below..