Understanding Equalization
Equalization, or EQ, is a way of controlling frequency bands of audio.
General Tips:
1 Hz cut
The issue of DC offset seldom arises and can be removed by using a 1Hz high pass filter.
20 Hz cut
Anything below 20Hz can be cut. The human ear can only hear down to about 20Hz so anything below that will simply cause speakers to do extra work. Using a high pass filter at 20Hz may minimize interference on other frequencies from those frequencies that our lower than the human ear can hear. Some mastering engineers recommend that a linear phase EQ should be used to cut out anything below 20Hz.
Getting Subs Right
A technique to help get a better understanding of the sub information is to listen to just the sub speaker while listening to several different well-mixed songs and then to contrast those against the song being mixed.
Creating Frequency Bands
First, create three stereo auxiliary tracks. Put an EQ bandpass on the first track that passes everything between 20 Hz and 50 Hz. Then put an EQ bandpass on the second track that passes everything between 50 Hz and 500 Hz. Finally, put an EQ bandpass on the third track that passes everything between 500 Hz and 20 KHz. This creates low frequency, mid frequency, and high frequency bands. Push the low frequency band to mono either by using a Mono_Maker, or by turning the volume down on one side, and center the other so that there are no phase problems. Try adding stereo imaging effects to the high band to increase width without muddying up the mid-band content.
Getting a Balanced Mix
One trick for checking the balance of your mix is to compare frequency bands between your mix and the benchmark mix. Isolate a range of about a half an octave and then sweep through different frequency ranges comparing the mixes. Be sure that both songs have been adjusted to the same RMS or LUFS reading before making the comparison.
Human perception is not very accurate below 50Hz and above 12 KHz. Anything outside of the 50Hz – 12 KHz range doesn’t benefit much from effects and is generally better left dry to prevent artifacts such as digititis and low-end smearing.
50 Hz
Put everything 50Hz and below in mono to tighten up the mix.
Narrow Qs
Use narrow Qs to find unsavory pops, crackles, and other bad sounds. Slowly sweep through the target frequency ranges to find any problematic sounds and then cut those frequencies as aggressively as you can without negatively impacting the track, using a very narrow Q.
Q is the frequency divided by the bandwidth (Q = Frequency / Bandwidth) with bandwidth being -3 down from the center frequency.
Baby Bumps
A baby bump is a small, high-Q EQ boost right by the edge of a high or low pass filter. For example, a baby bump at 85Hz next to an 80Hz high pass filter might help an instrument maintain a thick sound while also cutting out foot stomps and thuds.
Reverb
Always high pass reverb to remove rumble or thud like sounds. Don’t be afraid to try high passing reverb aggressively as it will likely prevent the reverb from making muddy frequencies muddier.
Frequency Carving
Some mixing engineers carve out frequency notches so that instruments have a range where they stick out. If you do any audio frequency carving, do it in the low to mid-range and not in the high end. The low end tends to have the most blurring and interference because of the lack of directionality in low frequency signals.
Linear Phase EQs
Some mixing engineers believe that parallel EQ, such as on a stereo bus, should only be done with a linear phase EQ to prevent phase issues. Some mixing engineers also have the opinion that high pass filtering should be done with a linear phase EQ to prevent phase issues in the low frequencies.
By Jack Johnston
Jack Johnston has a Master’s of Arts in Applied Linguistics from the New School University, a Master’s in Business Administration from Western Governors University, and a Master’s in Management and Leadership from Western Governors University.