From geeksandgod.com Audio processing II Podcast.
Always better to pull EQ's down rather than boost up.
20-20,000 hertz - human hearing
60 - Electrical cycle
Under 80, more can be felt than heard
100-500 (usually 200-250) is the "muddy" range - take this down to get rid of muddy
1k-5k - annoying guitar sounds
5k - magic number for human voice ("Presence")
7k - syballance - "ssss"
10k - "shimmer" - adds "pretty" but can get harsh
above 12k - not much there