Even the best microphone and vocalist combination can benefit from a little EQ adjustment.
While an expertly delivered vocal take is the most important part of a great-sounding vocal track, equalization (EQ) adjustments are also usually needed to improve the sonic impact of the recording. Even a great vocal performance can suffer if its tonal character is compromised by troublesome frequencies in the recording. With a little experimentation and subtle boosts and cuts in specific frequency ranges, the tonal quality of vocal tracks can be manipulated to maximize their effectiveness.
Before You EQ
It's important to avoid thinking of EQ as an easy way to rescue poor recordings. It always pays to work on getting the best possible vocal sound before any EQ adjustments are made. Experimenting with microphone choice and placement, as well as making sure that all cables and connectors are fully functional and free of crackles and buzzes, will help you capture a quality audio track. This way, the use of EQ will take the form of fine-tuning the vocal sound rather than trying to fix it.
Low Frequencies
If your vocal microphone has a low-cut filter, use it when you're recording. Usually, this filters out any frequencies below 75 Hz, which helps eliminate any rumble from the mic stand as well as taming any low-frequency plosive pops produced by the singer. When mixing, you may want to cut even more of the low-end, say up to 100 Hz or so, depending upon the vocalist. With a female voice, you can go significantly higher, since the voice is unlikely to occupy the lower frequencies. It's important to listen with a critical ear, especially if the voice has a full, lower register tone, to make sure that you don't eliminate frequencies that will negatively affect the singer's vocal character.
Fullness
For a vocal that sounds a little thin or nasal, try boosting a little in the 150--200 Hz range. Doing this will round out the sound and make the voice sound a little meatier. Be careful not to overdo this boost since you may make the mix sound a little muddy. If you have several voices in the mix, avoiding boosting them all in the same range will help alleviate this effect.
Boxiness
Sometimes a vocal track lacks clarity and definition. Such tracks are often referred to as sounding boxy or hollow, and the way to reduce this effect is to cut the EQ in the 4--500 Hz region. Try sweeping around this area until you find the offending frequency and cut from a narrow area so as not to remove too many of the middle frequencies. Cutting too broadly will be detrimental to the natural character of the recorded voice.
Presence
If the vocal track has trouble cutting through the rest of the mix, adding a little EQ boost in the 3--5 kHz range is often enough to give the vocal enough presence to be heard without raising its volume level. Simply raising the level of the vocal track can often make the vocal sound a little bombastic, almost like it's perched on top of the mix rather than a part of it.
Air
Boosting the higher frequencies between 6 and 12 kHz will give your vocal track a little more breathiness, or air. This can make the vocal sparkle, but it can also exaggerate the sibilant effect on "s" and "ch" sounds. Listen carefully for this excess sibilance, and try cutting a little around the 7 kHz area to lessen the effect.
