| All minimum phase filters have the same phase relationships. If you can duplicate the filter frequency curve, the result will most likely sound exactly the same (I've tried this). There may be some differences at high frequencies because of the z-transform, if these are meaningful I don't know (nobody uses the really bad algorithms anyway). Linear phase filters can sound different already because of the pre-echo, which is different from any other phase shift we have in EQs. Harmonic content generation, as I understand it is a form of distortion and clean digital EQs don't do this at all. If someone found a nice distortion model, he'd probably make a plug-in of it's own out of it or at least make the amount of distortion controllable (which I haven't seen in EQs).
Personally, I'm very skeptical about any digital EQ differences that are based on something else than filter shapes (BootEQ or some URS stuff) or pre-echo. In the analog world it's a different story, and the sound is also decided by something else than the actual processing (just putting the signal through quality hardware can make the sound better, they say) and distortions actually can become real. |