Bass EQ and “Sweet Spots”

Tune your EQ's frequency response so it sits better in a mix

by Craig Anderton

Equalization is crucial to creating a balanced bass sound that plays back faithfully over a variety of listening systems. But unfortunately, there are no “canned,” universally applicable EQ settings. Different basses and amps have different response anomalies that cause a build-up (or lack) of sonic energy at certain frequencies, and each instrument has its own sonic “fingerprint.” Room acoustics and miking also contribute to creating an unbalanced sound with respect to frequency response.

Equalizing bass generally requires addressing two broad problems: frequency ranges where the sonic energy is weak and needs boosting, and ranges where the sound is too strong and needs cutting. Recording through an amp will add more of these anomalies than recording direct, but even when recording direct, you may want to boost or cut certain frequency ranges for aesthetic (rather than “problem-solving”) reasons.

If you’ve recorded bass for years, after a while you can recognize where any problems lie, and instinctively know which frequencies need massaging to create the desired sound. But what if you don’t have years of experience? Fortunately, there are ways to analyze a sound’s character so you can identify the sweet spots and equalize them accordingly.

WHAT ABOUT COMPRESSION?

Because frequency response anomalies alter level at certain frequencies, and compression reduces the differences between amplitude peaks and valleys, compression may seem like a good way to even out the overall response. However, compression can color the sound in possibly undesirable ways. For example, only the peaks in a specific frequency range might be loud enough to trigger compression. This would yield a “squeezed” sound at those frequencies, while other frequency ranges sound more natural.

It’s preferable to get the best possible sound with EQ first, then add compression for further “smoothing.” One exception is if you’re using compression not to affect frequency response, but to smooth out variations in dynamics. In that case, it usually makes sense to compress first, then add EQ to change the tone.

FINDING THE SWEET SPOTS

To find the bass’s “sweet spots” for EQ, you’ll need a parametric equalizer with three controls: frequency, boost/cut, and bandwidth. A quasi-parametric EQ, which typically has a fixed bandwidth, might work—although in accordance with Murphy’s Law (“Anything that can go wrong, will”), the bandwidth will invariably be too narrow or too broad for the task at hand.

If possible, loop a “busy” portion of the bass track (e.g., notes that cover a wide range of pitches instead of just a single, sustained note). Looping is usually easy with hard disk recording systems; solo just the bass track (or mute all the other tracks).

Start by finding where the bass is most “aggressive.” Turn down the monitors, as we’ll temporarily be using significant EQ boosts to help find peaks. Then follow these steps:

1. Turn the parametric’s boost/cut control to lots of boost (e.g., 10 to 12dB).
2. Set the bandwidth to about an octave.
3. Slowly sweep the parametric frequency from high to low. Observe any meter that’s monitoring the channel, and listen carefully for any major sonic boosts.
4. Note the frequency range that drives the meter highest, or sounds the most distorted. There may be several such ranges; look for the most prominent one.
5. Try cutting the signal slightly in that range. This may create a more balanced sound. On the other hand, this frequency may be essential to the instrument’s timbre. Either way, you’ve at least identified the frequency or frequencies where the bass’s response peaks.
6. Adjust the bandwidth control for the best sound. If the frequency range is sharp, narrow the EQ’s bandwidth. If the range is broad, widen the bandwidth.
7. Go back and forth between steps 5 and 6 until the signal is balanced to whatever extent sounds “right.” As a reality check, occasionally use the bypass switch to compare the equalized and non-equalized sounds (Fig. 1).

Fig. 1: The top spectrum (from Sonar X3’s ProChannel EQ) shows the bass before EQ. This bass didn’t sit will in a mix because it was too “muddy” in the lows from a bass bump around 100Hz, had an annoying midrange peak in the 500Hz range, and lacked highs that were needed to emphasize higher overtones and pick noises. The lower spectrum shows how the EQ was adjusted to compensate for these issues.

Now let’s find the frequencies that are most important in determining an instrument’s intelligibility and “signature.” Follow the same general procedure as above, but in step 1, set the boost/cut control to cut instead of boost. Now as you sweep the frequency control, note what happens to the signal when you hit certain frequency ranges. Taking out frequencies around 60-100 Hz will affect the “bottom.” Frequencies around 700 Hz -1 kHz determine much of the bass’s intelligibility; a lot of the bass “snap” hits at 2-3 kHz, and “air” kicks in at around 5 kHz and above. Reducing these frequencies will reduce important components of the sound.

This data, coupled with what you learned earlier while boosting, is invaluable when doing a mix. For example, if cutting at 1.2 kHz reduced intelligibility, then you know that if the bass doesn’t “speak” well in the mix, try boosting at that frequency. On the other hand, if you found there was a major resonance at 130 Hz that caused the bass to sound “muddy,” cut the response a bit at that frequency.

ADDITIONAL TIPS

Generally, if cutting or boosting will accomplish the same result, I prefer to cut. For example, suppose that the high and low ends seem deficient. Rather than boost them, try cutting the midrange and raising the overall level somewhat. It’s a judgement call, but to my ears, sometimes this results in a more natural sound.

I’m not a big fan of EQ presets, because so often, choosing EQ settings depends so much on musical context. However, I still think it’s worth taking the time to store some of your favorite EQ curves. You probably won’t use the same curves each time, but what they will do is provide a point of departure that may shorten your “tweaking time” compared to starting from scratch.

Finally, remember that response anomalies can also be part of an instrument’s character, so don’t too extreme. Be especially careful about adding large amounts of boost or cut—even 1 dB can make a significant difference, and you want to avoid a situation where solving one problem introduces another. For example, you turn up the treble a bit, which then makes the bass less prominent . . . so you turn up the lows, and the combination of increased bass and treble makes the midrange comparatively weak, so you increase that, then the treble seems low and you start all over again . . . you get the idea. As with so many other audio processes, think scalpel rather than machete when doing sonic surgery.

  Craig Anderton is Editor Emeritus of Harmony Central. He has played on, mixed, or produced over 20 major label releases (as well as mastered over a hundred tracks for various musicians), and written over a thousand articles for magazines like Guitar Player, Keyboard, Sound on Sound (UK), and Sound + Recording (Germany). He has also lectured on technology and the arts in 38 states, 10 countries, and three languages.