This post is going to focus on getting a solid balance between the two main sources of bass in pop music: the bass and the kick drum.
Few things are better than mix that gets the low end right. It can be really tricky to accomplish (or downright impossible if the environment isn’t right). But, there are a few general conventions that can help in the quest for the right thump.
The Mix Environment
Before we can talk about making creative choices, it’s critical that the choices we make are made with an accurate perspective. First, it’s important to have some speakers that actually have some low-end response. The old standard of Yamaha NS10s probably won’t cut it here. Sure, you can tell if the bass is too strong because NS10s will fart out, but you won’t be able to tell how the bass relates to itself. I would recommend a pair of speakers that have good low-end extension of their own over a subwoofer. I have heard very few subwoofer systems that don’t leave me feeling like there’s a gap in response between the lows and the low-mids and, as a result , I’m a big fan of the Mackie HR series for just that purpose.
Next, set the monitors appropriately for your space. The HR824 series has settings for full, half, and quarter space. Whichever you would choose depends on where the monitors are in relation to the walls of the room.
Check your room for low-end resonance issues. If you find that your monitors sound tubby and your mixes sound thin elsewhere, try setting up some bass traps in the corners (these DIY tube traps work well, as do these commercial Auralex LENRD traps).
EQing the stereo bus can sometimes help but can’t replace a properly tuned room.
The Philosophies of Low-End Mixing
It’s common for electronic music producers to put a high-pass EQ on all instruments other than the kick and bass in order to achieve the clearest possible low-end. BT goes so far as to cut everything below 150hz. I generally don’t go that far – I like my vocals and acoustic guitars to have more body than that – but I almost always will begin rolling things off at 100hz where the bass isn’t necessary.
Low Bass, Snappy Kick
Traditionally, bass instruments such as electric bass or upright bass provided the majority of the low end of a song. Drums were usually recorded with room or overhead mics, producing a very live kick sound with less low-end extension. In these situations it made sense to have the bass instrument carry the beat and girth of a song.
This is still a common way to produce music, especially in styles that strive for an accurate, unhyped sound such as jazz and big band. With the increased proliferation of subwoofers and hip-hop style bass, this emphasis on bass over kick is finding its way back in vogue. Many RnB bassists love their low B strings, which also suggests merit in this approach.
If you do choose to use the close mic (most of the time peope do), room can be made for the bass instrument by carving out some of the close kick mic’s low-end. I often do a high-pass EQ shelf at 50hz or 60hz to take out the rumble, then I add a little bump at 100hz (or maybe 120hz if it’s a huge drum) – which is the punchy portion of the low, low end. SSL G series EQ is by far my favorite for drums, adding character the curve.
To compliment this, the bass can be allowed to breathe below 60hz and a bit of a notch can be applied where you boosted the kick. This will help the bass get out of the way of the kick drum impact.
If the kick still has too much body, consider scooping out a bit of the 250-500hz range, which is the thuddy area of the tone (it’s also where a lot of the richness comes from, however). If a jazzy sound is desired, it may make more sense to preserve the tone and simply pull the kick further back into the mix to get it out of the way.
Compressing the kick after this sort of EQ will create a very snappy sound at the expense of tone and resonance. Leaving it uncompressed will encourage the bass instrument to carry the beat as you will likely have to pull the kick’s close mic back to prevent its transients from monopolizing the dynamic range of the mix. A very woody, transient bass like an upright will do this this elegantly on its own, whereas something very girthy and sustained like a Moog synth will probably require some compression on the kick for it to have any stomp to it.
Resonant, Baritone Bass and Sub-Activating Kick
On the other hand, much of contemporary music, such as dance and rock, needs the kick to be powerful and dominant to convey the rhythm and impact of the music.
Contemporary rock bassists often prefer the more aggressive sound of a growl than the thud that was popular in the 60s and early 70s. Even bassists who downtune or use five-strings often scoop their midrange, leaving room for the kick to naturally fill the space (although special care will need to be taken in the ultra-lows below 60hz.)
In electronic music you will find that synthesized kick sounds such as the classic Roland 808 or 909 series introduce low subs not typically found in acoustic drums. These usually sound somewhat silly without their low end, so their bass is the priority as long as they are sounding.
I find it’s usually safe to invert the suggestions in the previous section: rolling off the bass instrument below 50hz, cut a bit of a notch out of the kick around 100 or 120hz and boosting the bass instrument to fit.
Compressing the kick with a fast attack makes sense in this situation, as does using a moderate speed compressor to smooth out the transients of the bass instrument. The amount to use depends on your tastes and the context, obviously.
Strong Bass and Kick
Sometimes it’s important that both the bass and the kick be subby, but not at the same time. In this case, you can apply a compressor or gate to the bass with the sidechain taken from the kick. This way, when the kick hits, the bass volume will be momentarily reduced to give the kick room to boom. Also called ‘ducking’, this technique is invaluable for hip-hop and dance music with strong synthesized drums and kicks. Not all compressors support sidechaining, so choose yours carefully.
Ducking can be overkill in many situations and sound weirds when applied to music that doesn’t suit itself to constantly ‘breathing’ with the beat.