Owner manual
15
P Section Low frequency band use
Simple Boosting or Cutting: Boosting or Cutting (attenuation) is marked on the front panel from 1 through
14, and further divided into tenths (e.g., a very delicate boost of 0.1 is possible). The equalizer is at at a setting
of 0 (knob indicator fully counterclockwise). Be aware that unlike modern shelving equalizers, the PEQ’s
boost frequency is specied at the frequency of maximum boost instead of the 3 dB down point. So 20 Hz is
a very useful choice with effect beyond 100 Hz, as shown in the curve below. As you can see, the 20 Hz boost
lter’s nominal center (3 dB down point) is about 50 Hz (so modern equalizers would probably call this a 50 Hz
shelf). In contrast, the 20 Hz cut lter’s nominal center is intentionally an octave higher—100 Hz. The 100 Hz
boost lter’s 3 dB down point is about 300 Hz, so it is really a very warm 300 Hz shelf extending well into the
midrange. Welcome to the world of the PEQ—enjoy its power and its quirks!
PEQ low frequency actual boost and cut frequencies are slightly different at the same setting
The Zen of the PEQ
The band interaction in the P-lter section is unique to its design; it has so much versatility that it’s like having
a four-band lter instead of two! With boost and attenuation on different controls, it is possible to deform the
overall response curve in a way completely different from using two bands of parametric or graphic EQ centered
on the same frequencies. This is the Zen of the PEQ, absorb it well…
Low frequency boost/cut interaction (sweetening the midrange): In the low frequency band, the mid-
frequency response changes when combining boost and cut because the attenuation (cut) lter occurs at a slightly
different frequency than the boost lter. The low frequency cut lter frequency is automatically placed an octave
higher than the boost frequency (there is no separate frequency control for the low frequency attenuation). This
has the effect of de-emphasizing the top frequencies of the boost and the frequencies above the boost. The result
is a dip in the range above the center frequency. This can help to open up the sound, without getting overly
aggressive at the center frequency. It preserves the basic tone, while still allowing you to tweak in a cleaner
and more present sound. For example, boosting the bass frequencies on a piano may cause some mud to be
perceived in the low-mid frequencies just above the bass boost due to harmonics and frequency buildup. By
adding some low frequency attenuation, these mid frequencies can be subtly (or drastically) attenuated. It’s like
having an additional parametric dip at your ngertips. The picture below shows how the most delicate colors can
be accomplished with this technique: the orange curve would normally be at by 300 Hz but the combination
has produced a subtle dip between 300-900. The red curve is still subtle but has a more aggressive upper bass/
midrange dip.