Mic Basics: What is Frequency Response?
Editor's Note: This post originally was published on March 3, 2009, and updated on August 10, 2017.
A microphone only does one thing. It converts sound into an electrical signal that can be amplified, recorded, or transmitted. But, there are a number of different characteristics that make microphones sound different. These characteristics determine a mic's suitability for a particular application.
In this post, we'll talk about frequency response.
What is frequency response?
Frequency response defines the range of sound that a microphone can reproduce and how its output varies within that range. The frequency response is the most significant factor in determining the sound signature of a microphone. The frequency response of a mic is represented graphically by a response curve. The two most common types are flat response and shaped, or tailored, response.
Below is an example of a frequency response chart. To learn how to interpret the chart, check out our post titled How to Read a Microphone Frequency Response Chart.
What's the difference between flat and shaped frequency response?
A flat response microphone is equally sensitive to all frequency ranges, so its response curve is in fact nearly a flat line. A flat response microphone reproduces the sound source accurately with little or no variation from the original sound. That's good if you're recording musical instruments or sound effects, but a mic with a flat response usually doesn't sound good on voices.
A shaped response microphone is more sensitive to some frequency ranges than others. Its response curve has peaks and valleys. Many microphones that have a shaped response are less sensitive to low frequencies, which reduces the pickup of both handling noise and the rumble from the stage when the mic is mounted on a stand. A shaped response microphone also typically has a boost in the upper mid-range, usually between 3,000 and 6,000 Hz. This is called a presence rise, and it enhances the clarity, or "punch," of voices and instruments.
Ideally, whether a microphone has a flat or shaped frequency response, a frequency response curve should be a fairly smooth line. If it has a lot of abrupt peaks and valleys, the microphone probably won't sound very natural, and it may have a greater tendency to cause feedback with a PA system.
Some microphones allow their frequency response to be adjusted to suit different applications. The most common adjustments are a low frequency roll-off control to reduce pickup of room rumble and a boost in the upper mid-range to enhance voice intelligibility.
Compare Flat and Shaped Frequency Response Sound Samples
Shure offers both flat-response and shaped-response microphones. Here are some samples of instruments recorded with both flat-response and shaped-response microphones.
*Note: The KSM44 used in this sample has been discontinued.