Randy Coppinger

Low Rolloffs

At last year’s AES Convention in San Fransisco I attended a tutorial by Alex Case on getting the most from equalization. Compare these two techniques for using low rolloffs (high pass filters) on directional microphones:

(1) Plosives and wind are lower and need a steeper filter, such as 12dB per octave or more.
For vocals and voiceover I typically set my LilFreq low rolloff to 100 Hz. The slope on that rolloff is 18dB per octave. This technique works much better if you apply the rolloff BEFORE compression.

Rolloff to Minimize Plosives

(2) Proximity effect is higher and needs a more gentle slope, such as 6dB per octave.
Take the example of a subtle microphone rolloff: 125 Hz with a slope of 6dB per octave. This is a conservative filter that makes a noticeable difference when the mic is moderately close in cardioid. As you move closer and/or increase directionality (hypercardioid, figure-8) you may want to use a higher filter to compensate for the increased bass heard from proximity effect.

Rolloff to Minimize Proximity

Can you use these together? Absolutely! I will often engage a mic rolloff and feed that signal through the LilFreq rolloff set at 100Hz before analog compression. And if the microphone’s rolloff still didn’t back off the proximity enough, I may add another filter. Of course there are approaches other than EQ, such as mic placement (more distance) and pattern choice (less directional). Please don’t use these filter examples as recipes, rather let them inspire your strategies for dealing with problems. The key is to listen for plosives, wind and proximity effect then consider how these EQ techniques might help make things sound better. Happy recording.

See also: Cascaded Low Rolloffs