please note for Edifier speakers with EIDC (similar to auto-gain control), you cannot set the bass too much otherwise the EIDC circuitry will kick in and thinks that it causes distortion. this explains the soften volume (one-pass equalization sound) effect.
affected speakers are Edifier Components speakers (such as C3, C2, HCS2330, etc) and MP300 so far that I know.
since HCS2330 features EIDC I am pretty sure you can't set too much bass otherwise it will be normalized by EIDC and causes unpleasant sound effect.