Regarding An Issue of "Drum Bleed"

11-05-2007, 05:35 AM

...the sensitivity of the mics isn't any problem in and of itself. Mics with high sensitivity just put out more electricity for a given sound pressure. Mics can't distinguish between sound pressure that you want, and sound pressure you don't want. A creature with a brain is required for that particular feat. (Mics can be more or less "selective" by having tighter or wider polar patterns, but if your unwanted sound is within the polar pattern, the mic itself is not going to reject it.)

the bigger issue is that the FOH rig is not the only thing "making noise in the room." The instruments and monitor rig are making sounds that are audible in the room as well, and the louder the monitors and instruments are, the more they are going to color the FOH mix. If the drummer's monitor is so loud that the monitor mix is louder than his drums are (at the mics), then the monitor mix is too loud.

Bleed is as big of a problem with vocal mics as it is with anything else. Especially in a small room, a big problem can be a lot of drums (and other backline, in certain cases) arriving at the vocal mics within the sensitive part of their polar patterns. (I have this problem a lot when a singer needs to be cranked - the drums come way up, along with the singer. Especially the cymbals - they're a great way to obliterate all vocal intelligibility.)

A gate can help with bleed, but only until it opens. If its open (to allow the singer to be heard), anything bleeding into that mic is coming through (although the singer is, hopefully, loud enough to help mask the bleed). Again, a gate isn't intelligent. Even if you can do all kinds of magic with the gate key input, filtering out as much spurious "triggering" signal as possible, the gate is still going to pass everything arriving at its inputs when it does open - whether it's "signal" or "bleed" is not something the gate can know. In a similar vein, gates can only help with feedback if they are closing off a signal before feedback can build up to the threshold. If the feedback is in the range allowed by any filtering on the key input, and is high enough, the gate is just going to let it on through like any other signal.

There are ways to get extremely high levels with incredible clarity and no feedback. Most of these ways center around high performance FOH loudspeakers, monitor loudspeakers, and excellent mics. These ways are very expensive, and still can cause permanent damage to the listener's hearing.

It's a lot cheaper, and easier on your ears, to fix bleed and feedback problems by turning things down until the problems go away. If nothing else in this post is intelligible (it's late), at least this should be.

Fighting battles by turning things up is hard. Fighting them by turning things down is easy.