The frequency spectrum of sub bass runs from roughly 20Hz to 60Hz. For reference, the low E on a bass guitar is at 41Hz. The lowest frequency the human ear can detect is around 20Hz. Let’s talk how to EQ sub bass to get it sitting just right in your mix.
How to EQ Sub Bass
The main things to do when it comes to EQing sub bass are being able to hear or detect it and creating space for it in the rest of your mix.
How to Hear Sub Bass
First, let’s point out that before you can EQ sub bass, you need to be able to hear it.
I recently compared headphones vs speakers in the context of mixing.
While they both have their benefits and strengths, headphones generally have a better frequency response in the low end.
Add the fact that you don’t have any room noise or distractions to contend with, a decent pair of mixing headphones is the best way to actually hear the sub bass in your mix.
To make sure that you can actually hear the sub bass, solo and sweep down from 60Hz to 20Hz. It’s likely that you won’t be able to hear beyond 50 or 40Hz on monitors. In the case of monitors, don’t take it as a limitation of your ability to hear lower, but rather the limitation of your monitors themselves.
You might want to check and see what the reported bass response on your speakers is meant to be, and make sure that you don’t have any on board high pass filters turned on to cut the low end prematurely (a common feature on studio monitors).
It’s especially important that you are familiar with how sub bass frequencies sound on whatever you’re mixing with, be it headphones or monitors/subwoofer.
Use reference tracks to know how a great low end SHOULD sound on your setup, and chase that sound on your setup when your EQ sub bass in your mix.
Drop a low pass filter around 80Hz on both your mix as well as the reference so that you can especially zero in on the sub bass. This helps you to get an idea of where to set your sub bass’ level as you mix low end in general.
You might drop a mono forcing plugin on both your reference and master fader to more accurately compare.
You can also rely on visual EQs like FabFilter’s Pro-Q 3 to see how much energy is in that sub region.
Drop a similar reference track into your mix with external out routing so it’s not being affected by any other buses including your master. Drop a gain utility plugin on that reference track and set it to match the volume of your mix at that time, then drop an instance of Pro-Q 3 after it as well as one on your master bus.
Split test back and forth and look to see where that 20-60Hz is peaking at during different times on each track. Note that the fundamental of the kick drum also exists in this region (see how to EQ a kick drum), so distinguish the kick from the bass when comparing each.
If you’re surprised at how much more energy your mix or the reference track has in the sub region, that is likely a reflection of the limitations of what you’re listening and mixing on.
Create Room
The most important thing to do to EQ sub bass is ironically not even on the sub bass track.
For a sub bass to sound its best, you need to carve out space for it via EQ on the rest of your mix.
To do this, you need to apply a high pass filter to literally every other track in your mix.
Outside of the kick and bass, there’s nothing in your mix which needs these frequencies, so an average high pass point of 100Hz will be more than enough to get most tracks out of the way of the sub bass, kick, and bass.
I put together an entire EQ cheat sheet which you can grab for free to see where I recommend high passing every instrument in your mix to create space for the sub bass as well as the kick and bass.
EQ Sub Bass
You can high pass at 20Hz as nothing musical is happening beneath this point. Use a relatively relaxed slope of 12db/oct starting at 20Hz. If you have a way to accurately listen to those frequencies then you can sweep higher. Otherwise if you can’t hear what you’re changing, it’s better to be safe and leave that high pass at 20Hz.
You can low pass your sub bass, but the exact point will vary depending on what your sub bass is doing up top. If it’s a saw tooth type synth sub bass, there’s going to be some grittiness in the mids and upper mids even.
Don’t be afraid to try low pass filtering all the way down to 100Hz on a sub bass to exclusively let that track/instrument represent just that: the sub bass frequencies.
Sometimes we think we need that top end character with certain synth bass instruments which represent the sub bass, then when we filter out everything above 100Hz via that low pass filter, the rest of the mix sounds so much more open and cleaner because those instruments which flourish in the mids and higher frequencies have that space to themselves.
Mixing is also a puzzle when it comes to frequencies, and the key to solving the puzzle is to carve out a unique space for every element.
Speaking of which, it’s common to have a conflict between the sub bass and the kick because their fundamentals are generally right on top of one another.
If or WHEN you have a conflict with the kick, you have two options.
First we have the classic method. You can use sidechain EQ (similar to sidechain compressing your bass to your kick) to get the bass to duck out of the kick only when the kick is playing. This creates room for the kick but also gives the sub bass a little extra feeling of life like it’s moving.
The other option is to try high passing the kick starting at its fundamental and giving it a boost at double that frequency for that first overtone. This keeps the bump of the kick represented while carving out more space for the sub bass.
Both these methods help the sub bass and kick work together when they’re fighting for that same frequency range, giving you a cleaner low end and a cleaner mix in the process.
EQ Sub Bass Tips
- The sub bass exists between 20-60Hz (lower is inaudible, higher gets into normal bass frequencies).
- Make sure you can actually hear your sub bass in order to make informed decisions (mixing headphones generally have a better bass response). To check this, solo these frequencies and sweep down with a low pass filter; ideally you can hear all the way down to 20Hz on whatever you’re using to mix.
- High pass at 20Hz with a sharp slope of 24dB/oct or higher to roll off inaudible frequencies.
- Use a low shelf or low pass filter at 200-300Hz to balance your sub bass relative to the rest of the instrument (in the case of some synth basses) or remove unnecessary frequencies, respectively.
- Make a dynamic EQ cut on the sub bass at your kick’s fundamental frequency (typically in the 60-70Hz region) and sidechain it to the kick to attenuate the sub bass there by a few dB every time the kick triggers to temporarily duck the sub bass from that important frequency. This creates a cleaner low end in general.
- Use a volume matched and mono engaged reference track to compare your track’s sub bass with the reference.