In my short experience, with audio and hifi, these are the Types of Equalizations I've noticed.
1. Source - Done at source mixing studio with dynamic range compression or other eq.
2. During encoding - If lossy encoding takes place. - Software equalization.
3. Soundcard DAC - Hardware equalization.
4. DSP - Hardware or software equalization. If you enabled it.
5. Amplifier - Hardware equalization.
6 Speakers - Hardware equalization.
7. Room - Hardware equalization.
8. Ear - Physical and biological equalization.
9. HRTF - Head related transfer function. - Crudely, how our brains listens.
From the above, the end user can tweak or modify the chain from 3-7.
All the best with your tweakings...
