Originally Posted by acef2
Id say EQ can not change sound quality. An EQ only affects frequency response -- it can not affect anything else in the signal.
But it does. Also, it not only affects frequency response but also phase response. Most headphones are single driver, minimum phase systems and therefore you can correct (aka equalize) both frequency and phase response with a min. phase EQ.
You can make a track sound better with EQ though, which is done in mixing, mastering and many times the end consumer does it as well.
Frequency response is the most important part of sound quality. Think about it this way: you have a headphone that has very low distortion but a 10 dB bass peak. Perceived sound quality will be ruined by the peak. EQ the peak away and you'll get a much more higher quality sounding headphone.
You can use EQ to make the bass seem different, but its only a mind trick (youre not doing anything but increasing or decreasing amplitude).
That's not a mind trick. Same as headphone with boosted or rolled-off bass are not mind tricks either. And you're not only changing amplitude, but also phase and therefore group delay just like the headphone driver does itself.
Regarding graphic EQs:
Adjusting the 180hz band will affect all sounds within its frequency range.
I've seen many graphic EQs with filters that not only work withing a single band but leak into the adjacent bands as well. Not what you'd expect by looking at the EQs user interface, but some EQs just work this way (without telling the user).
Aggressive EQing can introduce clipping in your music. You can avoid this by , as LFF said, "It is better to subtract, rather than add". Play with your EQ to learn what settings that introduce distortion, clipping and other artifacts.
I prefer to boost and cut where necessary and use a preamp* to avoid clipping. This way you can EQ with less filters, and higher sound quality.
*) kinda the wrong term since you can apply the gain after
processing the signal with the EQ, provided you're using floating point (like foobar2000 does internally for example).
The day you find your EQ lacking, get a compressor.
I definitely wouldn't recommend a compressor in a playback chain unless you know exactly what you're doing, and also not as a "better EQ".Edited by xnor - 4/28/12 at 4:39am