A couple of years ago I was doing a gig attached to a pro audio trade show sponsored by a speaker manufacturer. it was a weird gig at a club across from the convention center with two bands—my 10-piece soul review and a very good Ozzy Osborne tribute. Oh, and it was a really loud gig. (Remember, it was put on by a speaker company to showoff their system which generally means cranking it up pretty hard.) At sound check we were having feedback issues and the assumption was that it was a monitor issue (my band is usually in-ear but this gig was all wedges) But the sound company owner—who was trying to stay out of it and let his staff take care of things—knew I was using a condenser mic known for being very hot and pretty wide in it’s coverage pattern. The main P.A. was a line array also known for a wide pattern and after about 20 mins of trying to find the feedback in the system, he walked onstage, unplugged my mic and replaced it with a very narrow dynamic mic and the squealing magically disappeared.
It’s All About Heart…….
When you are in the studio you will find mics with many different pickup patterns including figure 8 and omni which picks up equally from every direction. But onstage—especially for vocal mics—you will find almost 100% of mics to be of the “uni-directional” type. You would think that uni (meaning one or single) directional mics would pick upsound from only one direction. But it is not that simple. What you actually get are several flavors of “cardioid” or heart-shaped pickup. The basic cardioid pattern looks something like this.
As you can see, at zero-degrees (or straight on) you get the full- response of the mic and it gradually falls off and dips to a theoretical level of zero at 180 degrees. The idea is to get the sound you want into the mic and reject the stuff around it. But it only works so well. Look at that plot again and notice that at 60 degrees off-axis the mic is still picking up 75% of what it does from the front. And for a very long time this was the norm. But new technology—especially new materials for the magnetic structure of the mic—allowed for some tighter patterns known as super cardioid and hyper-cardioid. This is what they look like:
As you can see, the response of these mics fall off a lot faster as you move off center. But nothing comes free. Look at the bottom of the plot and you will see that at 180 degrees the response is actually much stronger than the standard cardioid. So if you are using standard wedges for monitors they need to be placed at an angle and not facing you straight on. With a super or hyper cardioid, straight monitors means more feedback—exactly the opposite of a standard cardioid.
So What Does It All Mean?
A couple of things. First, vocal mics come in two basic flavors—Dynamic and condenser. Again if you need some basic knowledge about the two kinds of mics CLICK HERE for a more in-depth piece. What you need to know on a practical level is that condensers are generally thought to sound more “open” and “airy” than a dynamic and they generally provide a more detailed sound. But for a long time they were not suitable for live use for two reasons. First, they were fragile. Drop one and it would likely not work afterwards. Second they have a wide response area—at least as wide as a typical cardioid dynamic. But two things have changed that have made condenser mics pretty common especially among lead vocalists.
First they have become a lot more road worthy and second, the move toward in-ear or “personal” monitoring has greatly lessened the possibility of feedback from a mic with a wide pattern. (Note that this get more complicated as some very smart people are doing actual new development in the mic field. Specifically, live sound legend Bob Heil has released a line of dynamics that sound—by all reports—at least as good as most condensers and have a much tighter pattern. For a review of the PR-35, CLICK HERE.
So what is the bottom line? It really depends on stage volume. On a loud stage you need a tight pattern and that generally means a dynamic. (One sound guy I know who mixes a very big Nashville act calls one of the “standard’ industry condenser vocal mics the “moving drum mic” because it picks up so much drum sound in the vocal channel.) If you have a quiet stage or personal monitoring you may be able to enjoy the generally higher quality sound and greater detail of a condenser. (Having said that, i can’t wait to get my own hands on a couple of Heil PR-35s and put them up against a couple of my favorite condensers.)
What do i use? My band is on personal monitors so lead vocalists get condensers (a mix of Shure, Audix, Audio-Technica and AKG depending on the gig), but my mic locker contains plenty of very tight dynamics as well for those gigs where a condenser is too wide. As always when deciding what to buy it comes down to the eternal question: “What are you gonna use it for?”