Besides vocal mixing - I would say the most common question I read about on the internet is how to manage the low end. The kick and bass, or whatever else might be occupying that area, is the weight and power of a track. In addition, it's often the rhythmic backbone.
People tend to have a lot of trouble with low end, and I think there are two specific reasons why:
1) Harder to Hear
A lot of speakers and headphones simply don't reproduce the low end with great detail and accuracy. You really need large cones, preferably 8" or more to be able to produce the low end correctly. On top of that, rooms need a lot of treatment to manage the low end correctly. Parallel walls and corners tend to distort bass reproduction, making it hard to gauge what you are hearing. To complicate the issue - the actual bass range is much smaller linearly speaking than higher octaves. You can go from a sub bass A to a bass A in 55hz. In the upper ranges, 55hz might not even get you to the next note! Ultimately, this mathematically means your bass elements more readily over lap and leave you with less space to make things separate sounding and focused.
2) Frequency Perception
If you set a bass signal at equal amplitude with a mid-range signal, you'll perceive the bass signal as being quieter (see Fletcher-Munson Curves). This means it takes more juice for the low end to come out booming. Especially if you're going head first into some heavy compression, which is often the case for Dance and Hip Hop music. But hey, how important is having a big low end in Dance and Hip Hop? Oh wait.... So how do we get the low end focused and big?
Delegating Low-End Prominence
Before worrying about focused and big - assign one low end element prominence. Some people will do this by genre. I think that's dumb (well, semi-dumb). I like to assign my low end captain based on what element is most valuable to the rhythm. By genre, there are certain tendencies:
- Jazz you're going to be looking to the upright bass
- Dance you are going to be looking at the kick.
- Hip Hop is usually the kick, but it varies.
- Rock, it's probably a bass guitar, or even a low rhythm guitar.
Regardless - you want the low end to create movement, so you want to lean toward the element that does this in the most exciting way. Once you've figured out your low end leader, the rest is actually not terribly difficult (usually). Start with volume - get your main player at the right volume. That's the majority of the work right there. Then, get anything else in the low end to a level that's present, but not overriding the main element. Think of it as the co-star.
- Carefully assess the mid-range of the element. There's all sorts of good stuff living in that mid-range, and often times it's going to want to come out. Whether it's giving the kick punch in the low-mid region, or sharpening the attack at the treble area, or enhancing the gritty overtones of the bass in the mid-mids - check it out. Go with what feels right. Boosting mid-range won't make the low element bassier, but it may give it more presence in the mix and draw attention to the low end.
- Use the low-pass filter when appropriate. You only need one bass element to have a lot of high end, the rest is probably going to get buried under the mid-range instruments anyway - so get that high end out of the way and emphasize that deep low.
- Get aggressive. The low end is an open canvas for heavy processing. Even a completely flat, sustaining bass instrument can sound awesome over-driving into a compressor. The overtones activate and you get something just as flat, but a lot buzzier.
- Be careful with your compression on kick drums, specifically. You want a solid amount of attack to keep that kick drum drawing your attention, and a solid sustain to give that drum weight. It's hard to get both. And often times, though not always, the release of the kick doesn't sound so hot - unless you want that really trashy, weighty kick drum. Which can be cool.
- Embrace the sine wave tone. Sine waves are pure concentrated bass. They sound pretty great layered under a bass line, or gated to a kick. Just make sure the sine wave is playing the appropriate tones. Guess what - if your chord is changing throughout the song, that means the root that the bass resonates best at changes - so program your sine wave accordingly!
- Don't carve out low frequencies to make room for other low elements. Bass doesn't work this way too often. If you are carving out frequencies, do it because there's an excessive resonance there, or because there's sub build up.
- Don't be afraid of narrow boosts. Convention seems to say that you should boost wide. But in the low range - wide becomes very relative. Remember, there's less space in the low range - so a wide bandwidth is going to be super wide. Also, narrow boosts can help emphasize a good sub. Just be careful when choosing what narrow band - make sure it helps the bass element and fits properly in the context of the track.
- Don't feaking side chain every bass to every kick in every mix. Yes, ducking the bass from the kick can be a good way to get the kick in the open. However, the bass should be SUPPORTING the kick. And if it's supporting the kick, and you duck it out of the way - there goes your support. Also, remember that ducking has rhythmic consequences. In certain styles, where the kick is coming in regular intervals - this can be cool. When the kick doesn't come in regular intervals, or very close together, you start losing definition of that rhythm. I actually like to do the opposite. Long sustaining bass lines tend to have very little movement, and don't always aid the rhythm. I'll side-chain an expander, or an upward expander to the kick - so when the kick hits, the bass jumps a little with it.
In the track below - I actually do both. During the verse, the bass is chained to expand with the kick. In the chorus, the bass is chained to duck the kick. Oh, and there's a sine wave gated to the kick drum that's tuned to the root of whatever chord the song happens to be at.
Matthew Weiss is the head engineer for Studio E, located in Philadelphia, PA. Recent credits include Ronnie Spector, Uri Caine, Royce Da 5'9", and Philadelphia Slick.