The bass and kick are the foundation of your mix, and we want them to utterly dominate the lowest frequencies. I’m going to show you how to use a frequency analyzer to cut excess lows from every track in your mix, leaving clear, tight, punchy bass.
My favorite frequency analyzer is Voxengo SPAN. It’s free on both Mac and Windows, so grab it! Once it’s installed, load it on the master bus. Place the GUI where it won’t get covered up, or set it to “always on top.”
There are three settings we need to adjust, by clicking the “edit” button in the upper right corner:
Block Size – The higher the number, the more accuracy in the lowest frequencies, but the slower the refresh rate. 8192 is the best compromise on my system.
FREQ LOW – Lower it to 5 Hz to spot DC offset and other subsonic garbage.
RANGE LOW – This setting adjusts the display on the y axis. -100 works for my mixes, but let your eyes be the judge.
Track by Track
Next we check the low frequency content of every track in your mix except the kick and bass, and in most cases, insert a low cut (aka highpass) filter somewhere between 100-300 Hz.
Use your ears to set the frequency of the cutoff while the track you’re adjusting plays with the bass and kick. A 24 dB/octave filter is usually adequate, but if you’re seeing mountains instead of molehills, you might need to bump it up to 48 dB/octave. It’s okay if it sounds thin by itself, as long as it plays nice with the bass and kick. A good rule of thumb is:
Raise the frequency until the tone changes in an undesirable way
I usually roll off my vocals around 250 Hz, but sometimes I’ll roll off pads or guitars as high as 300 Hz. For meaty snares, I might go as low as 80 Hz. You don’t want to clutter the bass, but you don’t want to leave a hole either.
Kick & Bass
Does that mean that we leave the kick and bass alone? Typically, no.
We need to balance the sub bass with the rest of the mix, to get a deep full tone from the bass and a healthy “chest thump” from the kick without blowing out any speakers. Excess energy below 50 Hz also limits our potential for squeezing volume out of the mix in the mastering stage.
We could always just low cut the entire mix, but that’s ugly and imprecise. Even if we nail the frequency and slope of the filter, the EQ will add undesireable phase coloration and/or pre-ringing. It’s better to sculpt the low end on a track-by-track basis, balancing out the sub bass and shaping competing elements to reveal a powerful foundation for your mix.
Most mix engineers can’t even hear the bottom octave (20-40 Hz) because their monitors can’t produce it. Unless your room is 300 square feet or larger, and professionally tuned, adding a subwoofer will probably do more harm than good. We can’t always hear what’s down there, but with a frequency analyzer, we can see it.
I usually roll off the kick and bass anywhere from 20-50 Hz, sometimes not at all. Try loading in a few reference tracks, matching their volumes to your mix, and comparing. It’s all relative.
If you’ve ever set up a surround system, you know that you can put the subwoofer pretty much anywhere. Since bass is omnidirectional, we don’t perceive it as coming from one particular spot.
For that reason, it doesn’t make sense to spread the low frequencies of your mix across the stereo spectrum. It weakens your imaging and makes the mix sound narrow. Worse, if you’re cutting vinyl, it can make the needle jump out of the groove.
So as much as possible, we want the lows to be in mono. If you’ve got the kick and bass panned anywhere other than dead center, no lollipop for you!
To this end, cutting the lows from the effect returns makes a remarkable difference. I insert a low cut before the reverb/delay, typically at 250 Hz with a gentle slope to emphasize the high mids and highs. Higher frequencies are more directional, so highlighting that range in the effect returns makes for yummy headphone candy.
The end result is a tonally balanced mix with just the right amount of sub. I managed a relatively straight line from 40 Hz all the way to the top of the spectrum. Your milage may vary, and is heavily dependent on the arrangement.