The best open source alternative to DFX Audio Enhancer is Equalizer APO, which is both free and Open Source. If that doesn't suit you, our users have ranked more than 10 alternatives to DFX Audio Enhancer and four of them is open source so hopefully you can find a suitable replacement. Other interesting open source alternatives to DFX Audio Enhancer are eqMac 2 (Free, Open Source), A.R.I.S.E. Sound Mod (Free, Open Source) and PulseAudio Equalizer (Free, Open Source).
ARISE puts together sound enhancements like VIPER4Android, Asus Zenfone 3 libraries with DTS effect, Huawei MedaiPad M2 Harman & Kardon sound effects, Huawei P9 sound libraries, Lenovo K3 Note MaxxAudio, LeTv Max 2 Dolby Atmos, Sony LDAC Bluetooth codec etc.