I like the low bass end of most tracks, so when I’m producing music, should I just keep all of the low end? No. That would be completely wrong. Here’s why…
What is “the low end?” For me, it is that region of frequencies that is generally below 250 Hz. That is not a fixed number, so take it as a general rule, as it differs for almost everyone you will talk to.
The low end has a lot of names – not all of them good:
- Rumble
- Warmth
- Mud
- Boominess
- Subharmonics or Undertones
- Punch, 72-114 Hz
- Thump, 36-72 Hz
- Sub-bass (or just “Sub”), 10-36 Hz
The Wanted
Undertones
Subharmonics or Undertones (I like that word better) are frequencies that are sub-multiples of a fundamental. This means that a higher frequency fundamental or intended tone creates a lower tone. Sometimes this is a good thing as it gives “weight” to the fundamental tone by supporting it or, in other words, harmonizing with it.
These undertones can be enhanced or generated by different plugins for your DAW. A few notable ones that do this are Leapwing Audio’s Root One (enhance and generate) and Refuse’s Lowender (enhance only). I’ve used both, and these are well-made plugins, each with its own special features.
Ideally, I would like to have only one or, at most, a few instruments making noise in the low end. It depends on the type of music, but these are usually drums and bass and sometimes a synthesizer.
Good Vibrations
The sounds you get in the lowest of the low end, in the 30 Hz region, are felt more than they are heard. These are usually known as “Sub Bass” or just “Sub.” They are just vibrations when they are of such low frequency – you can’t hear them. I want this in my music because I want the audience to feel the lows and feel that bass. What I don’t want is for them to hear or feel a bunch of rumbles. I want those lows only when an instrument is intentionally making those lows. (That’s really important.)
In a range above 30 Hz but below about 70 Hz are frequencies you can both feel and hear. This is the range of the so-called “Thump.”
Further up above 70 Hz but below 120 are frequencies you can hear more than you feel, but you can still feel them a bit. These are the “Punch” frequencies and give music a dynamic low bass sound that comes at you when a drum hits.
Harmonic Creators
Waves Maxx Bass famously adds harmonics above the low fundamentals and simulates a strong bass by emphasizing certain frequencies above. It is quite an innovation and works incredibly well. But, the Waves plugins, while excellent, are difficult for me to use, so I use Leapwing Audio’s Root One instead, which does what Maxx Bass does and what Refuse’s Lowender does also. I’ve also used Wavesfactory’s Spectre, which exclusively adds harmonics of various types to anywhere you want in the frequency spectrum, which is a powerful tool for this sort of enhancement. If your track sounds a bit sparse or weak, consider adding Spectre’s various forms of distortion. Likewise if the highs are not crisp then add some higher frequency distortion. Pick the right kind. The Wavesfactory Spectre manual has some good recommendations.
Warmth
Warmth can be good for a track that is lacking body in the lows or low-mids. This warmth comes from saturation that can be applied in various ways. Boutique compressors and equalizers each can have signature warmth that is added through various forms of saturation. Wavesfactory’s Spectre also allows the application of harmonics to provide saturation and warmth of various forms and types. Tape machines traditionally have good warmth-creating saturation in the low-end region. Warmth can only be bad when overdone or applied incorrectly. Tape machines, for example, tend to smooth the signals going into them, thus creating warmth, that can smooth out the harshness in a mix but can also reduce the dynamic range if overdone.
Mono the Lows
Even with the low frequencies you have, you want to reduce the side information (make it mono) in the low end. I apply a high-pass filter (low-cut filter) at 120 Hz with a -6dB slope to the side channel. This effectively takes my low end to mono, making my music compatible with most speaker systems. it also gives it a grounded feel as the lows are centered and not all over the place. This further solidifies my mix and prevents that feeling of a rumble in the low end, even if I’ve already filtered it out elsewhere. Listening to this in a car becomes a more pleasurable experience as the speakers there are all nearby, and there’s less of a spacey feel to the music. You may think you’re losing a lot, but you’re actually improving your mix and your track.
You may want to target a different frequency to start your filter. That is perfectly fine. Just use a tool that can check that low-end mono compatibility for you, such as Sonible’s true:level plugin with this handy feature.
The Unwanted
Not all instruments should make noise in the low end, and those should be high-pass filtered with an equalizer from around 30 Hz or even higher. If you listen exclusively to the low end of an instrument and it sounds like a bunch of rumbling, loose noise, then it should be filtered out. This can be from around 70 Hz or higher on some instruments. Flutes, for example, should not be making much low-end noise, so filtering them out of the lows will not only declutter your low end, but it will make the flutes more clear and your mix more balanced. This goes for any instrument. The best way to do this is to listen only in that low end and selectively filter it until it sounds right. That will be different for everybody. (Note that this same rule should apply to the high frequencies, but we’re not discussing that here.)
I use a lot of field recordings in my tracks, and the low end on those is usually the rumble of wind or other unwanted garbage such as traffic, footstep thuds, or other noises picked up and transferred to the body of the recorder during recording through the tripod or other physically connected equipment. I try to remove these noises using Izotope’s RX, but sometimes I need to delete a bit more of the low end in the mixing process using an equalizer.
During live recordings, low frequencies can creep into any studio unless it is seriously isolated (room inside a room). This can be traffic nearby, trains, a hammering neighbor, or almost anything. These sounds are random and cause clutter in the low end of recordings, usually appearing as rumbling noises that are not reproducible. They are random and uncontrolled, and you do not usually want them.
Boominess often occurs when you have an instrument with a low end, but there’s too much of it. It overtakes the track, and all you can hear is a rhythmic booming sound. Sometimes this comes from a compressor on a bass instrument that is fed the low tone and can’t react properly. It is best to have good, clean, and well-balanced (spectrally) signals fed into a compressor, and most compressors famously cannot handle low frequencies so well because there is a lot of energy in the lows compared to the highs for the same perceived audio level. That’s why there is usually a high-pass filter built into most compressors so the lows can remain uncompressed and thereby not pulse or boom.
When there is too much unwanted content in the low end, it is really hard to mix the track. This is because there are no intentional signals in the lows but a bunch of, well, basically, garbage. But this garbage raises the levels in your music track and effectively eats up the headroom. We all know that low headroom can cause flat-sounding, very undynamic music, so this is another reason for cleaning up your lows.
The Equalizers
You can use any kind of equalizer to filter the low end, but I favor the kind where I can see the curves I’m applying. These are graphic equalizers with a visual display of frequency along the horizontal x-axis and decibels along the vertical y-axis.
Glossary of My Terminology
Track – a piece of music, fully formed, often called a song, and not an individual instrument in a mix
Channel – a single transmission line for audio in a mixer, often containing the sounds of an instrument or other audio
Bus – a single transmission line for audio in a mixer that contains more than one instrument or audio source, summed together
Plugin – an effect or instrument that can be used in a DAW, is often routed in a channel and a bus and is used to create a track or song
Equalizer – also abbreviated as EQ, this is a plugin effect used for altering the levels of frequencies of an audio source fed into it
Mid – the mid-channel of an equalizer passes only the sound information that occurs in both left and right channels at the same time
Mids – middle frequencies of the spectrum above the lows and below the highs
Mono (n) – the mid-channel of an eq, when listened in solo, will provide only mono and not stereo output
Mono (v) – the process of changing mid and side signals to only mid in a mix and removing the side information
Side – the side channel of an equalizer passes only the sound information that occurs in left or right channels but not simultaneously
Master (n) – the channel of a mixer dedicated to master plugins only and the sum of all channels and busses in a mixer
Master (v) – the process of applying finishing touches to an audio track before release
Mix (n) – the summed channels of an audio track excluding the master
Mix (v) – balancing and changing the dynamics of a track before mastering
Lars Lentz Audio™ 