Tips & Tricks

Duh, what's a null?

Many times during setup, on stage or in the studio, I will direct people on how to best angle a mic to put the "null point" in the proper position. Of course, this leads to the usual question, "Duh, what's a null?"

If you already read the article I wrote on polar patterns, you already know how crucial these diagrams can be to helping you use a mic to the best of its capabilities. Not only that, but by looking at the polar pattern you can visually see where the null point, or blind spot, is for that mic. Each one is different, of course, and has been placed there for a reason.

In simple terms, think of the null point as the spot where the mic does not pick up any sound. Try this simple experiment. Sing into a typical vocal mic like a Shure SM58 where the null point is directly to the rear, or 180 degrees. Now, as you sing, rotate your mouth around the mic in a 360 degree direction and you will notice that the mic picks up less sound the more off-axis (farther from the front) you get. So in the case of the SM58, where the null point is directly to the rear, it will not pick up any sound coming from the direction of the audience. If you want to hear the crowd, you gotta point the mic at the crowd, putting them on-axis and yourself off-axis. Starting to see the point?

Here are a couple of examples of how to use the null point:

1. You are miking two different drums, or a snare drum and a hi-hat. In this case, to avoid leakage from one drum to the other drums mic, you position the two mics so that each of their null points is aimed at the other drum, picking up only the sound of their respective drum or cymbal. Live or in a recording situation, you want to minimize leakage from one instrument or drum kit piece to another part. If you do have leakage, make sure it is good leakage, not just accidental leakage. More on leakage in the recording section.



2. You are setting up a vocalist who sings between two on-stage monitors angled directly at him. Pretty common. Since you don't want the mic picking up sound from the monitors (no feedback, please!) you could use a supercardioid mic which has null points directed at about 120 degrees. Right where the monitors are.



3. You are miking a vocalist who plays acoustic guitar. Using a Figure-8 mic which has null points to the sides, you can pick up his vocals and guitar sound with one mic while rejecting any noises to the side.

You get the idea. Use null points to your advantage whether recording or playing live. They are there for a very good reason. Now, go read about polar patterns.