How do you deal with comb filtering when recording in a live or untreated environment?

1 Choose the right microphone

The first step to deal with comb filtering is to choose the right microphone for the job. Different microphones have different polar patterns, which determine how they pick up sound from different directions. For example, a cardioid microphone rejects sound from the rear, while an omnidirectional microphone picks up sound equally from all directions. Depending on the source and the environment, you may want to use a microphone that minimizes the amount of unwanted reflections and ambient noise that reach the diaphragm. Generally, directional microphones, such as cardioid, hypercardioid, or supercardioid, are better suited for live or untreated environments than omnidirectional or bidirectional microphones.

2 Position the microphone carefully

The second step to deal with comb filtering is to position the microphone carefully in relation to the source and the environment. The closer the microphone is to the source, the less the influence of the reflections and the ambient noise. However, you also need to consider the proximity effect, which is the increase in low-frequency response that occurs when a directional microphone is placed very close to a source. You may need to adjust the distance and the angle of the microphone to find the sweet spot that balances the direct and the reflected sound, and that captures the tone and the dynamics of the source. You can also use headphones or monitors to check the sound quality and the level of comb filtering while positioning the microphone.

3 Use acoustic treatment or isolation

The third step to deal with comb filtering is to use acoustic treatment or isolation to reduce the amount of reflections and ambient noise that reach the microphone. Acoustic treatment refers to the use of materials, such as foam, fabric, or panels, that absorb, diffuse, or redirect sound waves in a room. Acoustic treatment can improve the acoustics of a live or untreated environment by reducing reverberation, echo, and standing waves. Acoustic isolation refers to the use of barriers, such as walls, doors, or booths, that block or attenuate sound waves from entering or leaving a room. Acoustic isolation can prevent sound leakage from other sources, such as instruments, speakers, or external noise. Depending on your budget and your space, you may want to use some form of acoustic treatment or isolation to create a more controlled and consistent recording environment.

4 Use phase inversion or EQ

The fourth step to deal with comb filtering is to use phase inversion or EQ to correct or minimize the effects of comb filtering on your recordings. Phase inversion is a technique that involves flipping the polarity of one or more signals to cancel out or reduce phase cancellations. You can use phase inversion when you have multiple microphones on the same source, such as a drum kit, a guitar amp, or a vocal ensemble. You can also use phase inversion when you have direct and reflected signals on the same track, such as a vocal recorded with a room microphone. To use phase inversion, you need to identify which signals are causing comb filtering, and then invert the polarity of one of them using a switch or a plugin on your mixer or your DAW. EQ is another technique that involves adjusting the frequency response of one or more signals to compensate for or reduce comb filtering. You can use EQ when you have comb filtering on a single track, such as a guitar recorded with a single microphone. To use EQ, you need to identify which frequencies are affected by comb filtering, and then boost or cut them using a parametric or a graphic EQ on your mixer or your DAW.