We all have favorite microphones that we prefer to use for particular applications. Some of the more popular suspects that engineers agree upon (!) include Shure SM57 on guitar cabinet, Shure SM58 for vocals, Sennheiser MD421 for bass cabinet, or AKG D112 for kick drum. The list could go on all day, and we could argue the pros and cons of the various tools we can’t live without.
Personally, when doing a live show, I want nothing other than a Shure 57 for snare top (in the studio, I’m open-minded, but lately partial to the now-discontinued Shure SM85 vocal microphone). Sometimes, however, the best microphone is not necessarily the smartest microphone choice. Let’s take a look at why.
The Size Factor
We’ll pick on tom mics as an example. I love the Sennheiser MD421 for toms, but on stage, the large body of the 421 can make it difficult to place without interfering with movement of the cymbals. It also hides the drummer — which may not be a good thing. For me, the Sennheiser e604 is a smarter choice because I can place them easily without worry that they’ll interfere with cymbals. Many engineers like to use small diaphragm condenser mics for toms. There’s no argument that they are easy to place, and a plethora of rim-mounting mechanisms obviate the need for mic stands, making it easy to pre-mic a kit in a festival situation.
All things being equal — and they never are, so take this with a grain of salt — small diaphragms tend to have lower mass resulting in faster response to transients than large-diaphragm condensers or moving coil mics. In fact, the diaphragm of a moving coil mic is considerably slower due to the fact that the diaphragm is “dragging around” the coil and wire. That characteristic makes a moving coil mic less sensitive to transients, and less sensitive in general.
The wide frequency response, fast transient response and high sensitivity of those small-diaphragm condenser mics means that they are capable of delivering a wide frequency response at both extremes, with plenty of low end as well as plenty of sparkle on the top. Those characteristics also mean that you’ll hear more cymbal leakage. If your drummer places their cymbals in close proximity to the toms, you may find that there’s a lot of cymbal leakage into those tom mics (especially if the drummer is hard on the cymbals). In fact, I recently did a show where I could hear the ride cymbal get louder when the gate on the floor tom microphone opened. Yikes. Reaching for the EQ in such situations can be counterproductive, because attempting to filter out the cymbal leakage by using a low-pass filter or high-frequency shelf EQ will make the tom sound dull.
I have found (YMMV) that a tom mic with a bit less fidelity and lower sensitivity (i.e. a dynamic microphone) makes a smarter choice. Those characteristics often mean tighter pickup patterns and less leakage. Those are important attributes in a live situation, as is the microphone’s pickup pattern. In the case of a tom mic, a super- or hypercardioid pattern may result in less cymbal leakage if the cymbal’s position coincides with one of the nulls of the pickup pattern (see Fig. 1). It’s true that many dynamic instrument microphones don’t possess the extended HF response of a condenser, so you may need to add a bit of EQ in the 3.5 to 5 kHz range or convince the drummer to try coated heads, but if the mic has lower sensitivity, then leakage from surrounding instruments has already been somewhat reduced.
A similar approach can be taken with vocal microphones, whereby it’s even more important that the application dictates the choice of tool. I love the way many condenser microphones sound for a lead vocal, but what happens on a loud stage when the vocalist moves away from the microphone? You have now added a cymbal mic to the mix. If you are using compression on that microphone and the compressor “let’s go” when the singer stops singing, the background noise (cymbals or the guitar amp blaring away behind the singer) will become even louder. Yikes again. If I were in a situation where I was doing an act that had a quiet stage (perhaps a jazz singer) and didn’t have to worry about instruments leaking into the vocal mic, then I’d certainly go for a premium vocal condenser microphone. But when you are worried about leakage from a busy stage, a less sensitive mic is your friend.
This is not an indictment of high-quality condenser microphones intended for stage use. Manufacturers battle every day to build tools that help us combat such issues — but it makes sense to compare a few choices and evaluate them not only on how they react to the source but also how they react to what we do not want them to capture.
Watch Your Figure
Omnidirectional (and, to a lesser extent, figure-eight) microphones get very little love on stage. The concept that a microphone can capture sound from the rear is far too much to bear in the face of avoiding our archrival: feedback. Think about what’s actually happening on the backside of the microphone. Suppose we are miking a horn on stage. Many engineers reach for a cardioid pattern mic, and there’s nothing wrong with that. Ribbon mics love horns, but the figure-eight pattern of most ribbon mics scares some engineers. After all, if we place a figure-eight mic on, say, a trumpet, the backside of the eight is facing the audience. Surely that will cause feedback. But not necessarily. Put down the remote and pay attention here: remember, you’re placing that microphone very close to the horn — probably within a foot. As a result the microphone “hears” the horn very loudly. What do you do with the gain setting on your mic preamp when the mic is close to the source? You turn it down, improving the signal-to-noise ratio of the chain in the process. The background noise is reduced. Yes, the back of the figure-eight is facing toward the audience, but think about how far away the room is relative to how far the horn is placed from the mic.
Ditto for using a figure-eight mic on a guitar amp (see Fig. 2), where the microphone is rotated so that the null pattern is facing the drum kit — meaning that the kit is rejected from the pickup pattern. Figure-8 mics for overheads? Sure, as long as you are in a room with a high ceiling. Reflections from a low ceiling will certainly make their way to the back of the pattern, causing phase issues and weird reflections but if the ceiling above the drummer is high enough, those reflections, will be greatly diminished by the time they reach the microphone. Sometimes, you gotta get outta the box!
Steve “Woody” La Cerra is the tour manager and Front of House engineer for Blue Öyster Cult.
