This chart shows the filter options offered by the AKG C414‑XLS microphone. Note the gentler slope of the 160Hz proximity effect filter (orange line)relative to the two rumble filter options (green and blue).
I noticed in your recent review of the Lewitt LCT 1040 microphone that it has a switchable 120Hz 6dB/octave high‑pass filter, for countering the proximity effect. If my microphone doesn’t have this feature, can I just set up the same thing in my DAW channel EQ — would that have the same effect? My microphone has only an 80Hz high‑pass filter and I tend to get too close to it and sing quietly too. So having this feature to reduce the proximity effect would be very useful. Hopefully my plan will work, as that Lewitt model is a little out of my price range!
SOS Forum Post
SOS Technical Editor Hugh Robjohns replies: Yes, you can replicate this in your DAW, and yes it will have broadly the same effect. However, performing this filtering within the microphone’s impedance conversion circuitry maximises the mic’s internal headroom and reduces the risk of excessive bass energy overloading any mic preamp the mic is plugged into. Nevertheless, when working with sources of moderate SPLs you can certainly apply a suitable corrective EQ in the DAW to achieve the desired effect. I’d start with a low‑shelf cut starting around 150Hz and experiment with the parameters to obtain the most natural‑sounding low‑end balance.
It’s worth adding that the filter options typically included in capacitor microphones are designed to do one of two things, and some mics have only one type or the other, while others have both. The Lewitt LCT 1040 has both types. The first, which you’re talking about, is the proximity effect filter. This is designed to correct for the bass boost introduced when the mic is placed very close to a source. It can be recognised easily, as it always has a gentle, 6dB/octave slope and generally has a turnover frequency above 100Hz (typically somewhere between 100Hz and 200Hz). The second type, known as a rumble filter, is intended to remove unwanted subsonic noise, which can be caused by mechanical vibrations or air currents. This kind of filter generally has a much steeper slope (12 or even 18 dB/octave) and always starts below 100Hz. Typical examples have turnover frequencies of 80, 60, or 40Hz, all well below the useful frequency content of speech/vocals and most acoustic instruments.