This also comes from somewhere here in the forum. I have had it forever and its a good general guideline. by no means is this absolute.
General Recording Information:
EQ and Frequency Response
This is a general guide for finding areas to EQ when mixing, remember not to OVER DO IT. Its always better to PULL frequencies then add them. Adding frequencies just ads noise!
50hz -
Increase to add more fullness to lowest frequency instruments like bass drums, toms, and the bass. Reduce to decrease the boominess of the bass and will increase overtones and the recognition of bass line in the mix. This is most often used on loud bass lines like rock.
100hz -
Increase to add a harder bass sound to lowest frequency instruments.
Increase to add warmth to piano and horns.
Reduce to remove boom on guitars & increase clarity.
200hz -
Increase to add fullness to vocals. Increase to add fullness to snare and guitar
Reduce to decrease muddiness of vocals or mid-range instruments.
Reduce to decrease gong sound of cymbals.
400hz -
Increase to add clarity to bass lines especially when speakers are at low volume.
Reduce to decrease boxy sound of lower drums like bass drums and toms.
800hz -
Increase for clarity and "punch" of bass.
Reduce to remove "cheap" sound of guitars.
1.5Khz- (probably the most problem frequency when recording guitar)
Increase for clearer, cleaner bass.
Reduce to remove dullness of guitars.
3Khz -
Increase for more attack of guitars.
Increase for more attack on low piano parts.
Increase for more clarity on voice.
Increase for more attack on the snare or other drums.
Reduce to increase breathy, soft sound on background vocals.
Reduce to disguise out-of-tune vocals and guitars.
5Khz -
Increase for vocal presence.
Increase low frequency drum attack.
Increase attack of piano, acoustic guitar and brightness on guitars.
Reduce to soften thin or tinny guitar
7Khz -
Increase to add attack to percussion instruments.
Reduce to decrease sibilance or that annoying ssss sound on singers.
10Khz -
Increase to brighten vocals.
Increase for slight brightness in acoustic guitar and piano.
Increase for hardness on cymbals.
Reduce also to reduce sibilance
15Khz-
Increase this will pretty much brighten anything, but use sparingly as this will enduce hiss