“I play drums in a rock band and I never seem to be able to get the kick drum loud enough in my drum monitor without it feeding back. I’ve tried different monitors in different positions, but it’s never loud enough. What can I do?”
As a live sound engineer over the years it was always astounding to me how LOUD drummers seemed to want the kick in their monitor. No matter how loud it was it seemed they couldn’t hear it, or really it was that they couldn’t feel it…until I figured out the problem. But before we get there I feel compelled to point out that traditional stage volumes of most bands are far too loud, and much louder these days than they need to be. Musicians are doing damage to their ears that will not be noticed for years, but is irreversible. Consider having your whole band (and you) switch to an in-ear monitoring solution. They sound much, much better than loudspeakers, and you have significantly more control over what you hear, which leads to better performance.
Now, back to your drum monitor. Needless to say it’s going to take a significant amount of wattage and a good speaker to reproduce a kick drum with the amount of power a rock drummer will like. And obviously the positioning of the monitor is going to have a tremendous impact on audibility and gain before feedback. But a third critical element is the polarity of the monitor with respect to the drum mics.
If everything in the PA/monitoring system is wired with correct polarity then you have achieved what is known as absolute phase (or absolute polarity), meaning, in this case, that an outward movement of the drum head produces an outward movement of the loudspeaker. In the PA system this is generally desirable, but in the drum monitor it is not. Think about it. You hit your kick drum, and the head moves away from you. At nearly the same instant your drum monitor’s loudspeaker moves toward you. When the drum head rebounds back the loudspeaker moves away. The drum head and the speaker are effectively out of phase with each other at your listening position. If you’ve never experienced what this does all you have to do is reverse the speaker leads to ONE of the speakers in your stereo system. You’ll notice a significant loss of low end. But it’s even worse than this…
While they are out of phase to your ears, they are actually in phase with each other. The drum head moves out, which causes the speaker to move out, which applies more pressure to the drum head, which moves the speaker more, etc… This leads to feedback. Run the drum monitor at the opposite polarity and you’ll get much more impact out of it and significantly reduce the tendency for feedback (depending of course on other variables such as what the house PA is doing, etc.).
Ideally the solution is not to reverse the polarity of the drum monitor though. This will help your kick, but may cause other mics to become a problem. If you can simply reverse the polarity of the kick drum only in the monitor system (which means at the monitor mixer) you have the ideal solution. The same thing should be done to any other mics that are placed on the back side of a drum head, such as a bottom snare mic (though the bottom snare mic is generally polarity reversed in the house mix as well, so it’s in correct phase with the top snare mic). If you can’t deal with the mics individually then reversing the drum monitor itself is probably still worthwhile. It can make a huge difference.