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
Randy Coppinger 
Very nice, Randy. I just tweaked my wife’s settings and am eager to find out if I will have less p-pop editing to do. (Do you remember my wife, Ticket Carson?)
I do remember Ticket, yes, but I’ll leave the tweaking to you. 🙂 Best wishes filtering.
Interesting. 12db slope for plosives/wind? I find that the steeper the slope, the less “natural” I feel like the EQ behaves (the less musical, the more artificial), which I suppose is to be expected. So I always go with the gentlest slope I can tolerate — but obviously: I’d rather have a steep slope than a plosive (the lesser of two evils).
Steeper slopes can get weird, no doubt, David. I have found that some EQs are better at steep slopes than others. I have also found that the lower I set a steep low rolloff, the less likely I will hear undesirable effects. So I think there is a tradeoff, which makes choosing a technique all the more significant.
At DCV I record the vast majority of voice through the LilFreq’s low rolloff set at 100 Hz. That’s an analog filter with an 18dB per octave slope. It sounds pretty great.
Some filters have a reciprocal boost above the corner that raises as the filter gets steeper. It may sound more natural in some cases, but can be especially challenging when trying to rolloff pops/wind. For these applications I prefer rolloffs that do not have a boost.
I’d say mic placement and pattern choice should be our first tools, followed by popper stoppers, and then strategic use of low rolloffs to minimize any remaining low frequency evils.
Absolutely (mic choice and pattern choice are preferred solutions first).
I bet analog EQ’s have an inherent advantage over digital EQ’s in this respect too.
Interesting that you use a filter (roll-off) to combat the proximity effect. I tend to try a low freq shelf for that. I have my “favorite curve” (I’d have to check the settings — I’m not in front of it right now) that I use for that.
Would love to know more about that shelf when you have time. Thanks, David.
Great information Randy!!!!
Thanks, Mike. I’m grateful to have learned these techniques from Alex Case and happily confirm them from my experience. Also, I’m in the process of writing another post about cascaded rolloffs for next week. Stay tuned…
Hey Randy! I love the vocal series. It truly has enhanced my vocal production, as well as the “mindset” to getting great vocal recordings.
One question: If you can’t get a hold of a 6dB high pass filter, would a low-shelf be a better choice, or use a 12dB with a lower frequency?
Thanks. Peace.
12dB will work fine. I like staggering a series of 6dB high pass filters, but sometimes you don’t have more than one, or a choice of filter steepness. In the end, do whatever sounds good in the context of the entire mix. Best wishes and thanks for the discussion.