Mic Basics: What is Frequency Response?

A Shure Educational Podcast

Part two of our three-part series on microphone basics. In this episode, Chris Lyons talks about the frequency response of a microphone, both flat and shaped.

Editor’s Note: This post originally was published on March 3, 2009, and updated on August 10, 2017. 

Edited Transcript

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.

Chart of Frequency Response in HertzWhat’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.

Visit the Mic Listening Lab to compare the sound of many more Shure microphones on vocals and instruments. Note the frequency response description and specs in each mic you compare. Keep in mind that the Lab uses “tailored” rather than “shaped,” but as noted above, they mean the same thing.

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Davida Rochman

Davida Rochman

A Shure associate since 1979, Davida Rochman graduated with a degree in Speech Communications and never imagined that her first post-college job would result in a lifelong career that had her marketing microphones rather than speaking into them. Today, Davida is a Communications Manager, lending her skills to a wide spectrum of activities, from public relations and social media to content development and sponsorships.

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  • J Lau says:

    This is an excellent topic that I’ve learned a lot. For wireless system, I have PG, PGX and PGXD and I can hear the difference. My question is, when I put a Beta 87A onto my PGDX handheld, it is almost the same with my PGX with Beta 58A through a Pioneer amplifier and Allen & Heath mixer. However you can hear the big difference as they are supposed to when hooking up to my Denon amplifier and BMB mixer. Does the amplifier and mixer affect so much of it ?

    • Davida Rochman Davida Rochman says:

      Thanks Jason, glad you liked this post. In regards to your wireless question, every part of the signal chain affects what you will ultimately hear, and different amps, speakers, and mixers can have a dramatic affect on overall sound quality.

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