When equalizing vocals, much of the work involves removing offending frequencies. We do so by cutting out a narrow band of frequencies.
Typical recommendations are:
- If there is too much low frequency rumble, cut down on frequencies below 80 Hz.
- If the vocals are booming, look for an equalizer that can put a magnitude reducing notch with a middle frequency somewhere between 100 Hz and 300 Hz, dipping down to, say, -30 dB, and a width at -3 dB of probably about 100 Hz. You would have to experiment by moving the notch up and down the interval between 100 Hz and 300 Hz to find the offending frequency band.
- If the vocals are boxy, do the same, but the offending frequency will probably be between 400 Hz to 500 Hz. (The higher the mid frequency, the wider the notch – see below).
- If the vocals are too nasal, look above 1 kHz to probably 2 kHz, but maybe even higher towards 4 kHz.
- If there is too much sibilance, cut around 5 kHz to 6 kHz.
In many equalizers, the width of the notch is defined by the equalizers "quality factor" (or Q factor). The Q factor is simply the ratio of the middle notch frequency to the width of the notch at -3dB. For example, if the middle frequency is 200 Hz and width is 100 Hz, then the Q factor is 2.
The Q factor is useful, because a constant Q factor will imply wider bands at higher mid frequencies, which is usually what is necessary in practices.
Higher Q factors for the same mid frequency produce narrower notches. Narrower notches are recommended for removing offending frequencies. Q factors between 2 and 4 should work well.
Some of the work involves boosting wider bands of frequencies. This may mean a Q of 1 or less:
- If you want more breathing room or air, add gain above 8 kHz.
- Sometimes I just want brighter vocals. I will gently increase everything above 1 kHz with a slope – the higher the frequency band, the larger the boost. Sometimes this produces sibilance and I complement it with a compressor with an aggressive ratio, but a mild threshold. (Sometimes I would have a sloping low end boost below 1 kHz for more bass, but that may produce muddiness and may require a high pass filter).
Fixing booming and boxy vocals
The recommendations above are not an exact science. Experimentation and listening over and over is needed.
In my latest experiments, I have two vocalists. Both vocals work best when applying a notch to reduce frequencies around 385 Hz.
The fact that both vocals use the same notch is a coincidence, of course.
I cannot guarantee that 385 Hz is exactly the middle of the notch. It is hard to say whether the transition from 385 Hz up or down the frequency diapason is equally steep in both directions. I do not know how the underlying frequency filter of the equalizer was designed.
Except for the difference in ranges of what is "booming" and what is "boxy" (e.g., 100 Hz to 300 Hz vs. 400 Hz to 500 Hz), it is not always clear to me how the two differ. In both cases, there are overwhelming and therefore offending frequencies that needs to be reduced. The causes of both could be similar. I suppose the cause of booming vocals can be recording in a small space, probably with an omnidirectional microphone, whereas the cause of boxy vocals could be close-miking with a directional mike.
My notch at 385 Hz is in the middle between "booming" and "boxy". Perhaps the vocals are both booming and boxy. But two notches would run the risk of completely hollowing out the vocals and, in either case, my equalizer does not perform well with two notches.
Fixing booming guitars
In at least two songs the vocals and an electric guitar follow the same melody.
In one case the boominess came from the guitar. When listening to the vocals by themselves, I found that they were good. The booming guitar was harder to notice during the first listen, but after 30 or so times, it caused headache.
My approach to taking the boominess of the guitar out was similar, but instead of a notch at 385 Hz, I used a notch at 315 Hz.
In a second case the guitar and vocals were both fine by themselves, but they occupied the same frequency range and did not play well together. In this case, I simply dropped most of the lower end of the guitar. I suppose I could have used a high pass filter, but that seemed like an overkill.
Fixing the drums
I still have one song left unfinished. It sounds good by itself, but it does not fit well with the rest of the album. The rest of the album is brighter. If I listen to the songs in order, the difference is noticeable.
During the past two weeks, I focused on the song vocals, trying to make them brighter. It seemed to me that this should bring this song closer to the rest.
This may be the wrong approach. The drums in this song are subdued and the hats and cymbals are too produced and too quiet. Maybe the difference is in the drums and not in the vocals.