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Dynamics Processors -- Application Tips

Chapter 10 -- Dynamic EQ Applications Beyond De-Essing

Auto-Correct Microphone Proximity Effect

Use Dynamic EQ to automatically correct for timbre changes due to the low frequency boost caused by the proximity effect of cardioid microphones (see Figure 28), which occurs when a singer/speaker does not remain a consistent distance from the microphone.

Two opposite applications share this problem:

1. The first occurs when the mic is located far enough from the person that the proximity effect has no bearing (typically a podium situation), then the speaker leans in closer to the microphone causing a low frequency boost.

Start with a 100 to 250 Hz center frequency, a bandwidth of 2.0 octaves and a ratio of 3:1. Set the threshold high enough so that when the person is the normal distance there is no response, and only when they move closer to the mic does the threshold kick the filter into action.

2. The second application compensates for the loss of the proximity effect as the person moves the microphone away from their mouth; typical of most hand held mics.

Solve this problem by perform the opposite routine as the podium mic example above. Have the person hold the microphone at the farthest distance from their mouth that can occur. Set the Dynamic EQ so that it is just below threshold. Once they move the mic closer to their mouth it will reduce the low frequency boost. Since we have become accustomed to hearing the proximity effect try low ratios so that the tonality change is slight, but remains more consistent than without the Dynamic EQ. Use appropriate EQ on the input channel to add back in any missing warmth -- this warms the signal while the Dynamic EQ keeps the tonality consistent.

Typical starting points are a frequency of 100 to 250 Hz, a bandwidth of 2.0 octaves and a ratio of 2:1 depending on the desired change in tonality.

Figure 28. Microphone Proximity Effect (courtesy of Shure Inc.) Low frequencies rise as the sound source gets closer to a cardioid microphone.

Auto-EQ Changing Sound Sources

A great example is evening out the tone, or timbre, of a guitar amplifier. Using two channels set up for different tones is very common to switch between a rhythm tone and a lead tone. Often the musician sets the lead tone brighter than the rhythm tone so it cuts through better. The problem comes when the sound system amplifies this all out of proportion, resulting in too much energy around 2 kHz to 4 kHz (a really nasty frequency range due to the ear's maximum sensitivity to this octave).

Setting the Dynamic EQ for a center frequency of 3 kHz and a bandwidth of about 1 octave cleans this up. Set the threshold high enough so that during normal playing nothing is happening. If the device uses relative threshold, once the lead channel is used it will automatically see the change in timbre and apply the Dynamic EQ to reduce the excess energy at 3 kHz relative to the rest of the audio spectrum. You can also use this technique to make guitar sounds "thick" and "chunky" without being overbearing by using the EQ section set in the 200 Hz range as well.

Improve Vocals

It is common for female singers to have a wide tonality swing when shifting from a quiet breathy passage to a loud crescendo. The voice sounds warm and pleasant during the quiet passage but shows a predominance of frequencies in the 1.2 kHz range for the loud crescendo. This is exaggerated when the singer moves the microphone away from her mouth thereby removing the warming character of the microphone's proximity effect and adds to the naturally occurring peak in this frequency range.

To fix this, simply set the EQ section to the problem frequency (typically 1.2 kHz) and set the threshold so that the compressor only kicks in when she sings the loud passages. Use the ratio control to determine exactly how much of the original tone change remains -- low ratios leave more change while high ratios clamp down hard and allow very little change.

Create Radical Sounds

Dynamic EQ lets the user create sounds that change tone with level, or at extreme settings, which allows the creation of radical sounds based on the threshold, attack & release times.

Experiment -- the results will amaze you.