For a singer, flat is not good.
For a tire, flat is not good.
For beer, flat is not good.
But for audio equipment, flat is great. Problem is, many manufacturers have forgotten what “flat” means!

I have in my hands a spec sheet for a microphone from a well-respected pro broadcast manufacturer. Among the features, it brags about the “flat-and-wide frequency response.” The accompanying frequency response graph looks like a relief map of the Rocky Mountains. Within the normal range of this mic, the variance is as much as 15dB. You call that flat?!
[/ rant]

Let’s remind ourselves what “flat” is, and why it’s a good thing:
Frequency response charts show the variance from ideal reproduction. If OUT exactly equals IN, then the line is at “zero” all the way across the chart (no variance). Let’s call this ideal characteristic line… oh, I don’t know… how about… FLAT.

When OUT does not equal IN (the device can’t accurately process what was applied to the input), the difference is plotted above or below the reference line. The lower the accuracy of the device, the bumpier is the line. This is the opposite of flat. (see the graph at the top of this article)

Electronic devices (mixers, amplifiers, and the like) are pretty good at making a reasonably flat frequency response. By the time a piece of audio makes its way through all of the circuits in the station, it still sounds like the original signal. Think of what the result would be if every mixer, distribution amp, delay unit and recorder altered the sound a bit before sending it to the next unit. Once the creative folks (we’ll talk more about them in a minute) are finished with the audio, we don’t want the equipment to randomly change the sound of the piece. We just want it delivered intact.

The larger challenge is microphones and speakers, as they have to convert acoustical energy to electrical signals, and vice versa. They also deal with mechanical variables such as diaphragm material, air pressure, etc. Absolutely flat response is much more difficult to achieve. It’s in these categories that we often choose between “flat” and “pleasing.”

Almost every microphone alters the sound that it receives. Recording studios collect lots of different mics so they can find one that works well with the singer or instrument being recorded. Broadcasters have identified some specific mics that do nice things to the spoken voice. These are definitely not flat, but in this case it’s a creative decision.

Production Room speakers should be as flat as possible. They are usually identified as “reference monitors.” You need to have confidence that what you are hearing is exactly what is on the recording. For example, if your production speakers are bass-heavy, your EQ decisions will sound completely different to a listener whose speakers don’t match yours. If your speakers are neutral, the sound will reliably translate to the largest variety of listeners. In the Production Room, you aren’t listening for pleasure… you need accuracy.

The on-air studio can use speakers that have a distinct “personality” to their sound. Nothing the on-air person can do will alter the sound being sent to the listeners. These speakers are just for listening. Choose some that make you feel good. If they impress visitors, that’s good too.

Sorry to go on and on. I feel much better now. Oh, rats… my coffee has gone flat.

4 thoughts

  1. Amen! The latest line of so-called audio “experts” will blankly look you in the eye and swear they’ve got a great product that produces a flat response. Most of the time, it is blatant crap. A trained ear can decipher the manipulated spectrum long before even looking at the items accompanying graph. Great article BSW, and thanks for the rant!

  2. To be sure that the “flat” microphone is “flat” we must also compare it to a known “flat” microphone to make sure our output source is flat.

    So do we know that our output source is flat?

  3. The article is great, but I think the on air studio has to be as flat as possible too, especially when mixing background music with live voiceovers. You could be thrown off by freq. response anomalies.


    Director of Production
    WACC Miami.

  4. Just a couple of comments.
    1. Great discussion. Thank you.
    2. Jon, Why would you need to compare
    a microphones frequency response plot if you
    created it with a known flat source such as an oscillator and known flat source transducer in a chamber? I do agree that using another microphone which has been calibrated is a good method.
    3. Mandi, I would not consider studio responses and mixing anomolies when speaking or measuring microphone and other transducers because they should be measured and treated separately and when making measurements you first want to eliminate as many variables from your baseline measurements and calibrations of each device or system. Then when all that is done, you can later consider the studio effects and mixer effects which I do agree should be considered.
    Thanks for a great forum people!
    Jack Gott

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