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Mixing DI Bass Guitar

Understanding & Avoiding The Pitfalls By Dave Lockwood
Published August 2022

Mixing DI Bass Guitar

Ever had trouble getting a plain DI’d bass guitar to sound right in a mix? Me too, sometimes! But it’s almost always fixable once you understand the issues.

Getting the bottom end right is often the difference between a polished, professional‑sounding mix and something that never quite realises its full potential, and that usually means both capturing and mixing a good bass guitar sound. On occasion, a clean, unadorned DI bass guitar sound is exactly what’s wanted in a mix. But even when the sound of a miked speaker is the preferred sonic outcome, many people still choose initially to record a ‘clean’ signal by connecting the bass guitar to a DI box or the high‑impedance instrument input on their audio interface, since it’s often just the most pragmatic option.

Using a DI allows low‑volume or even silent monitoring, of course, but also removes the acoustics of the room as a consideration. That’s often helpful because bass amps and their associated speaker cabs aren’t the easiest things to record with mics, especially in smaller rooms where unpredictable cancellations can occur due to interactions between room boundaries and the long wavelengths involved. Furthermore, a clean DI track offers up the widest range of options for modifying the sound when mixing.

A lot of recording musicians, though, seem to struggle to get a DI’d bass part to sound right when it is in a mix. So, in this article, I’ll be explaining what it is about a clean DI’d bass sound that can make it challenging, and I’ll take you through some techniques that should help you get closer to the kind of result you may be seeking in your productions. Whilst there are some very capable amp‑modellers, speaker IRs and clever bass‑enhancement plug‑ins available, you won’t need them for this. I’m going to be employing only basic plug‑ins such as the EQs and compressors available in any DAW, alongside some simple editing and routing strategies.

I’ll assume that you already have a project with a single, mono track of DI‑recorded bass guitar, and monitor speakers or headphones that allow you to hear a satisfying amount of bass when you listen to commercial mixes. If you’re unsure about the accuracy of your monitoring, try importing some good‑sounding commercial tracks into your DAW, install an EQ set to flat in all bands but with the spectrum display active, and examine the overall frequency shape of the audio. Note particularly where and how steeply the bottom end rolls off, and then see how some of your own mixes compare. Try to achieve a broadly similar shape of roll‑off, and you shouldn’t end up too far wrong. If in doubt, err on the side of caution: too much deep bass is always more destructive in a mix than too little.

If in doubt, err on the side of caution: too much deep bass is always more destructive in a mix than too little.

DI‑agnosis

First, let’s consider the problem we’re trying to overcome. If you use a good amp/cab simulator pedal or a bass‑specific DI pedal with EQ and dynamics at the recording stage and, crucially, get all the settings just right, you may not have a problem at all, but a plain DI track on its own can often seem a bit bland and incomplete‑sounding, especially in a busy, or up‑tempo mix. This is because electric bass guitars were originally designed to be used with amps and speakers, and without those components the spectrum DI’d straight off the pickup simply isn’t what we’re accustomed to hearing. Typically, there’s far too much midrange and the bass end doesn’t have enough of the ‘thump’ and resonance needed for a contemporary mix.

Figure 1: Typical frequency response of a single 1x15 bass speaker cabinet.Figure 1: Typical frequency response of a single 1x15 bass speaker cabinet. Figure 2: Typical frequency response of a single 4x10 bass speaker cabinet.Figure 2: Typical frequency response of a single 4x10 bass speaker cabinet. Figure 3: The averaged spectral balance of a clean DI’d Fender Precision bass guitar.Figure 3: The averaged spectral balance of a clean DI’d Fender Precision bass guitar.If you compare the averaged spectrum plots for two types of bass amp and speaker combinations (Figures 1 and 2) with the plot from a Fender Precision bass captured using just a clean DI box (Figure 3), you can, literally, see the problem. In the 1x15 speaker plot, the 500Hz midrange area is more than 15dB below the peak in the bass area that sits around 150Hz, whereas for the DI signal that difference is more like 5‑6 dB. In the 4x10 plot, the difference is even greater (over 20dB). Fortunately, electric bass guitar has no ‘natural’ acoustic sound for our ears to reference, so we can get pretty radical with EQ and dynamics processing to ‘bend’ it into the kind of shape that best meets the needs of our mixes.

Another reason why mixing bass, and especially DI’d electric bass guitar, is perhaps more of an issue now than in the past is that expectations have changed significantly in recent decades. Listen to popular, commercially successful recordings from the late 1960s, through the ’70s and into the ’80s, and you’ll often hear the bass end come and go a bit, according to which range the bass is playing in. In contrast, the bass in modern recordings in almost any genre, and particularly the amount of deep bass, is far more consistent and ever‑present, and mixes in which the bass doesn’t permanently underpin the harmonic and rhythmic shape of the track just don’t seem to sound professional any more!

So we have two broad issues to address: one of fundamental tonality, and the other the consistency of the bass part in the mix. Of course, in discussing this issue at all it has to be accepted that a wide range of different outcomes might be sought — the sound of an effective bass line can vary massively, from the no‑treble depths of a reggae bass part to the clanking grind of classic punk rock. Still, it’s almost certainly the case that the musical role of the bass will be the same whatever the context: meshing with the drums to provide the rhythmic pulse of the track, whilst also underpinning the harmonic structure of the chords and top lines.

Key Pointers

With all that in mind, then, let’s consider how you might best approach mixing DI’d bass guitar. There are so many variables in play (different genres, different basses, different playing styles), so nothing can be absolutely guaranteed to work for every situation, but let’s start with some tips that are as close to being universally applicable as it gets:

  • Always mix bass in context. By all means solo the part to search for fluffed notes or noises, but tone and volume must be decided alongside the other instrumentation; what it sounds like on its own is irrelevant.
  • Because the perceived bass level can vary significantly with playback volume, it helps to maintain a consistent monitoring level.
  • When equalising in the lower octaves, try to use only wide‑band EQ (unless you’re addressing a specific resonant peak or dead spot), as narrow‑band cuts or boosts can start to affect individual note levels rather than tonality at very low frequencies.
  • To fix uneven playing, opt for edits rather than compression — if a compressor is correcting the performance, then it can’t do what you really need it to.
  • If other parts are competing with the bass guitar in the lower mids, the bass has to ‘win’. So be prepared to carve frequency space out of other instruments.
  • Sometimes, when a bass track isn’t working, it’s not the fault of the sound at all. Rather, it’s the playing or the part that’s wrong, and you really won’t be able to ‘fix it in the mix’.

You’ll probably have noticed that my list doesn’t include the ‘old favourite’ tip of making sure that your bass guitar and kick drum address different areas of the low‑end spectrum. Certainly, if you’re going to dial in a significant low‑frequency peak for both signals you’ll want those peaks to be in different places. But how about just not creating the problem in the first place? Better, in my view, to shoot for a smoothly extended bass‑guitar signal that can co‑exist happily with the lower peak of the kick drum, wherever you need to place it.

On a similar note, if you’ve consumed enough ‘Internet advice’ on this subject you might imagine that you can’t start mixing a bass‑guitar track without setting up ‘ducking’ from the kick. But you need a reason to use ducking. Four‑to‑the‑bar kicks combined with a hard‑quantised, fat, synth bass sound in a high‑bpm track can be cleaned up with a bit of ducking, and side‑chain compression can be used as a deliberate effect too. But a properly EQ’d bass guitar really should be able to coexist with the kick, with neither having to push the other out of the way; moments of ‘useful summing’ are retained as part of the natural dynamics of the performance.

Get The Bass‑ics Right

A good bass sound in your mix starts with a good bass sound, which requires a good bass — one that’s reasonably even in output both across its strings and up and down the neck. Many basses have hot spots and may have dead spots too. So what constitutes ‘reasonably’ even? Something like a general lack of resonance towards the bottom of a low‑E string, and especially a low‑B on a five‑string, can be dealt with pretty easily. But, for example, a low F‑sharp that just dies on you will be problematic.

Good players don’t only learn the idiosyncrasies of their instruments: they’ll also learn how to voice a part for recording too. If you’re playing a riff that consistently involves the E at the seventh fret of the A string, it doesn’t help if some of those notes are played using the E at the second fret of the D string instead. It might work fine on stage, but that sort of tonality change is really noticeable on repeated listening, particularly under the microscope of recording and mastering processes. Even on a really good instrument, the general change of tonality between the E and A strings versus the thinner D and G is something worth bearing in mind when preparing a bass part for recording. I’m sure I’m not the only engineer to have edit‑replaced all the notes played in the ‘wrong’ part of the neck for more consistent‑sounding ones from other parts of the track!

James Jamerson, the Motown bass genius, was always DI’d, but his sound is primarily the result of the old, very dead, flatwound strings he favoured and the foam‑rubber string mute built into the bridge cover of his Precision bass. Combine that with his technique of playing every note with a single right‑hand finger just beyond the big chrome pickup cover, and you have a warm, consistent sound not really typical of a DI at all.James Jamerson, the Motown bass genius, was always DI’d, but his sound is primarily the result of the old, very dead, flatwound strings he favoured and the foam‑rubber string mute built into the bridge cover of his Fender Precision bass. Combine that with his technique of playing every note with a single right‑hand finger just beyond the big chrome pickup cover, and you have a warm, consistent sound not really typical of a DI at all.

There’s a similar consideration with regard to the (right‑handed) bass player’s right hand, which applies equally whether they play with fingers or a pick. Notes played just in front of the bridge have a very different attack and tonality to the much rounder tones found by picking nearer the end of the neck. There are valid reasons why you might want to switch from one to another during a track but, in general, it’s not helpful if you want to achieve a consistent bottom end in a mix.

The avoidance of any of the above issues goes a long way towards simplifying the task of addressing the tonal issues that we’ll move onto in a moment. Before you start trying to mix, though, do try to get the track tidied up with a bit of DAW editing. Any notes that are obviously too loud or quiet can be isolated into individual regions and have their gain tweaked to make them more even in level. Don’t leave this job to a compressor, since it can be done better with editing. If the levels are way off, then the tonality and envelope might sound different enough to warrant substituting a note in from another take or another point in the performance. It’s also worth muting any significant gaps in the bass track — even if you can’t hear anything, there will often be noises that could become evident later, such as when applying some mix bus compression.

Remedial EQ & HPF

I like to start shaping the sound of a DI’d bass with what I call ‘remedial EQ’. Figure 4 is a frequency plot showing the difference between a DI’d passive bass signal and the average of two speaker cabs. This gives us a broad target for EQ that should counter some of the issues I described above. We can add or subtract from such a curve later, for tonal reasons, but this almost always gets me into the right area to start with. (At this zoomed‑out level, different basses don’t change the outcome much so can be ignored as a variable; even a five‑string instrument seems to benefit from this treatment.)

Figure 4: The kind of ‘remedial’ EQ curve we are looking to achieve, in order to turn our clean DI signal into something more powerful and consistent that will work well in a contemporary music mix.Figure 4: The kind of ‘remedial’ EQ curve we are looking to achieve, in order to turn our clean DI signal into something more powerful and consistent that will work well in a contemporary music mix.

There are several ways of arriving at something like the overall target response shape, but a standard DAW EQ plug‑in does the job perfectly well. It’s important to note that, while you’re lifting the bass region, you should avoid creating a prominent peak there. You want a smooth rise and fall. Also, because you’re boosting where there’s lots of energy it pays to work at ‘safe’ levels that leave you plenty of headroom. Don’t start this process with a bass track already peaking near 0dBFS!

I suggested above that EQ’ing should normally be carried out whilst listening to the spectrum of the mix as a whole, but you can start getting rid of any spurious very low frequencies in solo mode. Even inaudible LF energy consumes headroom and can mess with any compression you apply. The fundamental of the bottom E on a four‑string bass is 41Hz so, theoretically, there shouldn’t be anything lower than that — but there often is! So slope it off with a 30Hz high‑pass filter (HPF) at 12 or 18 dB per octave.

EQ In...

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