? If you've done any amount of researching online via home recording forums? you've probably heard of experienced engineers recommending to younger engineers to use less microphones. Why? The reason is simple. If 2 microphones are at different distances from the source the signal will arrive at each microphone at a different time. This means the wave may be going up while entering one microphone but may be down when hitting the next instrument (The wave may in between going up and going down as well or may be going up at one frequency and going down at another frequency).

This causes phasing or comb filtering problems.

Phasing and comb filtering are subjects that every audio engineer should study. They are beyond the scope of this article, but you may want to check out a better explanation of phase and comb filtering in the music recording glossary.

I will say that comb filtering is one of the most destructive factors in any recording situation. I've tried using multiple microphones many times on guitar cabinets and on more than one occasion, I sat down to mix the next day and said “AAAAHHHH!!” because the guitar sounds was nasally, unfocused, and lacked impact. This “can” happen if EXTREME attention to detail isn't payed to the position of the microphones.

If you are using cheap mic stands, you may have problems with comb filtering on some songs. I've noticed when mixing several songs on the same day that the guitar tracks slowly went out of phase. I finally figured out why when I noticed that one of my microphones wasn't staying where I put it. The mic slid down about 3 inches and caused extreme damage to the tone of the guitars. Because of the mega fast nature of that recording, I just didn't catch it in time. (This is a big reason I don't try to record albums in a weekend...or even a month anymore).

The lesson here is that if you are using 2 microphones and one mic moves even an inch or two, you'll notice extreme changes in the recorded guitar tone.