Frequency response of microphones and monitors – why to care

The craft of microphones and sound monitors is flooded with audio theory. In a studio, we want them to sound exactly as they are meant to. You might say that they are no different from the rest of your gear, but there is one detail that you should always keep in mind when choosing which microphone and monitor are best for you, their frequency response. In sum, it refers to the range of frequencies, and is a measurement of a device’s magnitude and phase output in response to an input signal. Technical definitions apart, do you really know how it works? How does it affect your work? Hopefully today's topic should help clarify some of these recurrent questions.

How does the frequency response affect my work

Before we break down the topic you have to understand that frequency response isn't just about whether there’s too much bass, mid, or treble coming out of a system. Although it's a big part of the equation, there's a lot more involved. From the source audio files to the amplifier and speakers, frequency response will play a major role and it can potentially mislead (even ruining) our listening experience. However, it works differently for microphones and monitors, and that's what we will see next.

Graphic response chart

Before we go further, let's see the representation below of an iZotope Ozone 5 equalizer. The picture represents frequency curves of a male vocal sample. If you don't know what is frequency, check this article I just linked first. It has quite a deep tone, isn't raw, it has a reverb effect in it. The screenshot has been taken during the playback of the vocal, let's see it: But how exactly do we read it? It may just look like a lot of doodles in a graphic, but it's a lot more than that. The horizontal line represents the frequency range, and it goes from 20 Hz to 20 kHz. The vertical measures are in dB (decibel). The graphic below has a few examples of instruments and the frequency region where they usually act. Note that I'm not taking into account tonal nor instrument variations, which always affect the frequency charts. It's merely a general representation, you can listen the instruments I've analyzed in this YouTube video. The closer the instrument is to 20 Hz, the lower the frequency (eg basses, kick drums ...), the closer to 20 kHz, the higher the frequency (eg high pitched noises like cymbals). Now that you have a slightly better understanding on a graphic response chart, let's see how it works on monitors and microphones.

Frequency response for monitors

For monitors you should always look for ones that give you a flat response, with minimum deviation (typically ±3 dB). The reason is very simple, you don't want them to "color" your mix. By that I mean that you don't want any kind of enhancements into your mix (nor masking). The typical human hearing is able to pick up from 20 Hz to 20kHz so that's where the frequency response is usually measured. But note that anything below 30 Hz tend to be more felt than heard. It's important to remember that a flatter response won't always sound good. "Sounding good" is very subjective, it depends on personal taste, the individual hearing, cultural preferences, etc... Which is not the point here.

Choosing monitors

So, how do I choose the monitors for my studio? What should I look into when looking for monitors? Let's see a few extra points below.

• How do vocals and instruments sound? Do they sound natural? If the answer is no, you might want to keep looking for other monitors.
• Does the monitor tend to emphasize any instrument (or frequency) over the other? If the answer is yes, you got yourself a bad monitor (that's more common than you think, happens a lot with basses).
• I'm I looking for any specific brand? Not particularly, but there are a few in the market that I can recommend, like Presonus – Eris E5 Studio Monitor, Yamaha – HS8 Powered Studio Monitor, M Audio – BX8 D2 Active Studio Monitors, among many others, there is a really interesting article to read here.

Last but not least, trust your guts, try before you buy. I understand that it's not always possible, that's why we have reviews and articles like this on the internet.

Frequency response for microphones

It works differently for microphones. Firstly you have to consider what are you going to record with it. Guitars, vocals, drums...? For each specific sound you could opt for a specific microphone that has a frequency response that matches it. For instance, a microphone with a frequency response range of around 80 Hz to 15 kHz would make a good choice for a vocal microphone. The reason is that those are the frequencies that usually vocals act within, which makes things easier afterwards during the mixing process. Below I'll list a few reasons why you should NOT opt for flat frequency response microphones.

1. They won't focus in the instrument frequency region which should get more attention;
2. As result (from the point above) you'll have a dirtier mix;
3. The recording will sound dull.

Different microphones for distinct sounds

A good recording is the one that needs fewer cuts and modifications in the mix. There are microphones that already help cut through the mix, the flat definitely does not. The flat frequency response microphone is mostly used just for measurement, which in music is practically used just for recording orchestra, in the deca-tree formation. In conclusion, choose the microphone based on the instrument you're going to record, response curve and subjective empirical auditory test. But note that the instrument to be recorded depends not only on its fundamental frequencies, but their harmonics. There are a few examples of microphones particularly good for a specific recording of an instrument, based on its frequency response. Take the Shure SM57 for instance, as it is particularly good for instruments like snare drums. Snares frequencies resides around 150 Hz to 250 Hz range, right where the SM57 frequency chart shows that it's flat or neutral. Besides that, it's a dynamic microphone, extremely resistant and can withstand a lot of sound pressure. Another great example is the BETA 58A, also Shure's. It's enhanced frequency range within 2 kHz to 10 kHz make it a great choice for vocals, as it adds brightness and intelligibility to the voices.

How acoustic treatment affects the mix

Lastly, after taking everything else into consideration, don't forget that the acoustic treatment of your home recording studio also plays its part on the mix. Let's see if you empathize with the following story: "...You have finished the mix and master of you latest recording. It sounded so great that you couldn't wait to show your friends, so you have exported it to your flash drive. Your friends came and picked you up with their car and you decided to play the new track in the car's stereo. You got extremely embarrassed because it sounded nothing like in your studio!..." The most likely reason is that because there are some serious issues with the frequency response of your equipment. Or maybe the acoustic treatment of your studio just sucks. The reflections in your room might be causing a boost in a specific frequency range, so you've cut it to compensate. As a result, once you played the recording in another system you noticed a significant loss in that specific area. You understand now?

When fixing the recording/mix doesn't work

Worst part is that you'll take the recording back to your studio to fix it, but you just can't, because the room gives you the impression that there's nothing to be fixed. And so it goes on. That's quite frustrating, you got to admit. Consider yourself lucky if you've never been in that spot. I'm just talking about frequencies here, but the same could happen with echos, standing waves, and so on... You should always try to avoid that. But if even after carefully analyzing every corner of your room you are still getting that sort of issue, consider using a digital room calibration software, might help fixing any minor issues you still have. In conclusion, my advice for you is to take everything here into consideration. Learn as much as you can about reading and analyzing graphic response charts, frequency response and how to make an appropriate acoustic treatment. At the end your recordings might still sound bad, but you are right on track to improve your work, so... don't give up and try again!