Tips & Tricks
Frequency Response & Polar Patterns
Who cares about microphone graphs? Frequency response graphs? Polar pattern graphs? They look like a bunch of squiggly lines superimposed over a fancy graph, but what do they do and what should they mean to a musician?
Here is the scoop...
Most musicians pick a microphone to sing or place in front of their amp for a couple of reasons. Pick one or more that apply to you:
- The mic looks cool.
- Your favorite star uses the same one.
- Somebody suggested it.
- You got it free.
- You did a lot of research, checked out the frequency response and polar graphs, tested a few different mics, and then figured out what sounded best for your vocals or amp.
Most people I know pick 2 or 3. Very few pick 5. However, once you know what you are looking for and how to read them, both a frequency response graph and a polar pattern graph can be extremely helpful in choosing a mic for stage or studio use to maximize an artist's voice or instrument.
Frequency Response Graph
The frequency response graph first: This chart is like a character snapshot of the microphone. It tells you without even hearing the mic, how it responds to frequencies that are thrown at it. For example, if you look at the chart for a typical vocal mic, the Shure SM58, you find a nice "presence peak" that starts around 2 kHz and then dives down around 10 kHz. Knowing only this, you now know that the mic will emphasize the upper mid-range frequencies that so many vocalists like to hear.
The same graph shows a low frequency roll-off around 100 Hz, indicating that the mic will not pick up many of the low rumblings such as people moving around on stage or in the studio, or bass frequencies from the bass player and kick drum. Using this same idea, you could easily find a mic to use for various drums or other instruments that emphasize the frequency you want to hear or record, and not the ones that interfere with other instruments.
A wise studio engineer once told me, "If you have to EQ on the sound board more than just a touch, you probably used either the wrong mic, or placed it badly. Fix that problem first, then EQ only if you have to."
Polar Pattern Graph
The polar pattern graph is a little different in that it shows you the sensitivity of the mic versus the angle at which the sound wave is hitting it. Looking at the graph, the farther the lines are from the center of the circle, the stronger that signal is at that particular angle. Look at the polar pattern graph for the Shure SM58, and you can see how at the 180-degree point (the area directly behind the mic) very little sound is picked up. This, in effect, isolates the vocalist from background noise like the audience or other musicians.
Different mics have different polar patterns. Extremes might be an omni-directional pattern where the mic picks up sound from all directions (useful to mic an entire room) or a figure-8 pattern, where the mic picks up sound from the front and back but not the sides (useful to mic a vocalist and his acoustic guitar for example). By looking at a mic's polar graphs, you know immediately from where it will pick up sound and how best to implement the mic for your purpose. Check out a good variety of different patterns here.
So there you go. Just by glancing at the frequency response and polar pattern graphs, you can know from which direction the mic will pick up sound, and how the mic will handle the frequencies of what you are trying to mic. I actually keep a notebook of these graphs for each of the mics that I commonly use or run into so that I can easily refer to them.
Hey, if nothing else, the next time you go mic shopping, ask the sales guy what the polar pattern for that mic looks like. You will probably just get a blank stare from him. So strut your stuff! Tell him the graph is in the box (it is always included), and then go ahead and show him how to read it, too. By then you will probably have a crowd that is way impressed by your technical knowledge!
