There are a lot of filter responses: notch, bandpass, peak, allpass, high pass, lowpass, shelf…now let’s add the “table” response to the collection.
Parametric EQs can add peaks and cuts that are broad, narrow, or anywhere in between, but they all have slopes on either side of the filter frequency. The table response described here can boost or cut over a range of frequencies, with a flat response over that range. This avoids having to dedicate several overlapping parametric stages, which still doesn’t achieve quite the same result. The key to this response is combining shelving EQs.
Table Response Boost
To boost a frequency range, set the low- and high-shelf frequencies to the lowest and highest frequencies in the range (Fig. 1). Use the Shelf setting to determine how quickly the boosted section returns to the flat response. I’ve found the 12 and 24 dB settings works well, because the Q control comes into play. This can provide additional modifications to the response, which we’ll cover later. However, for the gentlest effect, 6 dB is valid in many situations as well.
Figure 1: This table response, inserted before a high-distortion amp sim, gives greater sensitivity to midrange notes and also trims the highs and lows for a “tighter” sound.
But we’re not done quite yet. To provide an actual boost, increase the output Gain control for the desired amount of boost. For example, if you want the table response to boost +12 dB, set the high and low shelf Gain settings to -12 dB, and the output Gain control to +12.
Table Response Cut
Similarly to the boost option, set the low- and high-shelf frequencies to the lowest and highest frequencies in the range you want to cut (Fig. 2). Again, use the Shelf setting to determine how quickly the boosted section returns to the flat response; the same general comments about how the shelf slope works with boosting apply here too.
Figure 2: This table response for a drum loop cuts back on the midrange a bit to help emphasize the kick and the snap/sizzle of the share and high-hats; it also reduces any “midrange mud,” and makes space in that frequency range for other instruments.
Cutting requires an equal and opposite approach to what we did for boosting. If you want the table response to cut 4 dB, then boost the shelf controls by +4 dB. Then, set the output gain control to -4 dB. This restores the shelf boosts to flat, and adds the desired amount of cut for the specified frequency range.
When cutting with the low shelf or boosting with the high shelf, increasing resonance by turning up the Q control adds a peak just above the shelf’s corner frequency, and a dip below the corner frequency. When boosting with the low shelf or cutting with the high shelf, increasing Q adds a peak just below the shelf’s corner frequency, and a dip above the corner frequency. This emphasizes the extremes of the chosen frequency range, while also increasing the depth of the cuts near the corner frequency. Try adding resonance to the low shelf when using this technique for vocals, particularly narration (Fig. 3).
Figure 3: The table response adds a bit of a low-frequency boost (with Q) to give the “late night FM DJ sound,” but also cuts lower frequencies to reduce p-popping. Meanwhile, the high-frequency shelf emphasizes the voice’s articulation, while reducing extraneous highs, hiss, and sibilance.
Of course, the table response doesn’t replace a parametric. But sometimes, it might be just the response you need, and you’ll find it faster to dial in the right frequency range by moving the shelf controls than trying to make multiple stages of peak/boost EQ do what you want.