How to Buy a Microphone Wisely [An Advanced Guide]

When I set out to buy my first microphone, I encountered something called Decision Paralysis.

Have you ever gone to a restaurant with a menu that had hundreds of dishes? It becomes so difficult to make a choice, right?

This Choice Paralysis in turn spoils the experience.

I faced something similar with Microphones as I was overwhelmed with the innumerable choices that existed out there.

Buying a Microphone turned out to be more than just spending money and I had to get it right! Out of experience, I knew that using the wrong Microphone can result in bad recordings which are a pain to correct in the Mixing stage.

So here I am, with an Advanced Guide on how you can buy your first Microphone and make the right choice!

Right from the function of a Microphone to advanced topics such as Polar patterns and Frequency Response, I’ll cover it all in this article.

What does a Microphone do?

The basic function of a Microphone is to capture the acoustic energy fed to it and convert it into an electrical signal.

Acoustic energy can be any form of Pressure Variation. It can be a human voice, a dripping faucet, a car horn, a radio or a dog barking. In simple terms – Anything that makes a sound.

A microphone converts that pressure variation or acoustic energy to an electrical signal measured in Volts. That’s it, it’s that simple.

Fun Fact: The human ear works in the same way as a Microphone. The acoustic energy enters the pinna, moves the ear drum and eventually gets converted to an electrical signal that our brain is capable of understanding. 

What are the types of Microphones?

There are many ways in which Microphones can be categorized and this is the exact point where the confusion begins. I’m going to explain it step by step and in the easiest manner possible.

Category 1: Based on Environment

Ask yourself – Are you going to record or amplify a performance with it?

This is an example of how Rode has primarily categorized it.

They have made it really easy by dividing microphones that you can use in the Studio (to record) and the ones that you can use for Live performances (to amplify).

Category 2: Based on Sensitivity

Sensitivity is a very important parameter of a Microphone and based on this parameter, microphones are classified into two broad categories:

1. Dynamic Microphones.
2. Condenser Microphones.

What is a Dynamic Microphone?

Dynamic Microphones are low sensitivity mics mostly used in live performances.

What is a Condenser Microphone?

Condenser Microphones are high sensitivity mics mostly used in Recording Studios.

What is the sensitivity of a Microphone?

Sensitivity is how much of an output signal a Microphone generates for a specific amount of input signal.

In simple words, if your mic picks up the softest sounds in its vicinity, it has high sensitivity.
If it tends to ignore the soft sounds and captures only the loud ones, then the mic has low sensitivity.

The fundamental difference between a Dynamic and Condenser Microphone is sensitivity.

Here’s the difference between Rode NT-1 (a Cardioid Condenser Microphone) and Rode M1 (a Live performance Dynamic Microphone):

Notice the difference in sensitivity? Have a look at the mV reading in front of sensitivity for both of them.

For NT-1, it is 35.00 mV @ 94 dB SPL
For M1, it is 1.60 mV @ 94 dB SPL

Let’s understand what these values actually mean.

Remember the function of a microphone? It was to convert acoustic energy to an electrical signal measured in volts.

35.00 mV and 1.60 mV is the amount of electrical signal that these mics produce as output when fed with 94 dB SPL. mV stands for milli-volts.

Now, what does SPL stand for? It stands for Sound Pressure Level.

Imagine a scenario at night when there’s absolute silence. Silence signifies imperceptible pressure variation in our vicinity.

Suddenly when a dog howls a second later, the pressure variation in the environment becomes perceptible because our ears are able to sense that variation.

SPL is the change in air pressure from silence to that dog howling. It’s a relative measurement.

One can also conclude that NT-1 is approximately 35 times as sensitive as M1.

Imagine using NT-1 at a live concert, the output would be all over the place. Firstly, it would be blaring. Secondly, it will capture every little sound from corners you can’t even imagine. So in this scenario, using the M1 makes more sense.

Similarly, in a studio setting where the acoustics are controlled, you’d want to capture the nuances of a vocalist, the whispers, perhaps the husky tone. Capitalising on a highly sensitive mic makes total sense here. Hence, NT-1 would be a much better choice in a studio.

Do you now see why the M1 has especially been tagged as a Live Performance Dynamic Microphone?

Also, you now understand how the environment and sensitivity go hand in hand.

Category 3: Based on Polar Pattern

Have you ever noticed someone at a conference holding a mic too low and at an angle that makes his voice inaudible or unclear at times?

Do you know why that happens? Because a mic is designed to pick up sound differently at different angles. Otherwise, the sounds around a mic would be captured in the same manner as in front of it.

That’s how human ears function too. If someone is standing in front of us and speaking, we hear them differently than someone who is standing at our back. This is the exact thing a mic is trying to replicate so that when we hear the recording, we also get a sense of space.

What is Polar Pattern?

Simply put, the Polar Pattern of a Microphone defines its sensitivity at different angles.

Here’s how Rode has categorized their microphones on the basis of Polar Patterns:

Cardioid Polar Pattern

As you can see in the image above, Rode NT-1 is a Cardioid Condenser Microphone.

Why do you think Rode has mentioned that within the description of NT-1? That too at the beginning.

It’s because Polar Patterns hold a lot of importance AND, Cardioid is the most common Polar Patterns found in Vocal Microphones.

Before we look at the Polar Pattern of NT-1, I want you to imagine a 360-degree field around the Microphone. Done?

Let’s begin.

Under the basic specifications, you can have a quick glance at what a Cardioid Polar Pattern is:
“Picks up audio from the front and side and rejects from the rear“.

If this information seems sufficient, you need not go deeper. If not, look at the circular graph below it.

• 0º signifies the front of the mic.
• 180º is the rear.
• 90º and 270º are the sides.
• The three black circles marked -2.0, -10.0 and -20.0 are the relative decibel readings that signify sensitivity.

Next, let’s look at the red-outlined shape with a frequency of 500 Hz. Notice carefully:

• At 0º, the red shape is around -2 dB (along with all the other colours/frequencies).
• As you start moving towards 90º and 270º, the red shape starts to move towards -10 dB.
• At 180º degree, it’s around -18 dB or so (extremely low sensitivity).

Here’s the interpretation:

• The mic will be most sensitive to sounds that are right in front of it.
• When you start moving to the sides, the sensitivity will start decreasing slowly.
• The mic will pick bare minimum sounds from the rear.

Omnidirectional Polar Pattern

Here’s how one of the polar patterns in Rode NT2-A looks like:

The basic specification – “Omnidirectional – Picks up all sides equally”.

Have a look at the graph and you’ll notice how vastly different it is from Cardioid.

Omnidirectional, as the name suggests picks up sound from all directions with equal sensitivity.

Figure 8 Polar Pattern

Rode NT2-A has multiple polar patterns. The second one is Figure 8.

The basic specification says – “Picks up from the front and rear and rejects the sides”.

This looks like a weird polar pattern, right?

But can you guess why this polar pattern might have been invented?

The first, most basic reason could be to record two voices at the same time. Lead vocalist and backing vocalist recording at the same time like a jam session. The second can be a guitarist and vocalist recording at the same time. For that matter, any instrumentalist can join the vocalist at the same time.

Super Cardioid Polar Pattern

To explain this, I’m going to choose Rode M2 which is tagged as a Live performance Condenser Microphone.

But didn’t we just discuss that Condenser Microphones are highly sensitive and shouldn’t be used in live performances?

Let’s take a look at the specifications of M2 and compare it with Rode NT-1, a Cardioid Condenser Microphone:

Take a look at these (M2 & NT1):

1. Sensitivity: 6.30 mV & 35.00 mV @ 94 dB SPL
2. Polar Pattern: Super Cardioid & Cardioid

Can Condenser Mics be used in live performances?
Yes, they can, if the microphone’s sensitivity is low which you can clearly see here.
Another thing is the polar pattern, here’s why:

Have a look at the basic specifications of M2:
“Supercardioid – Picks up the front and sides and rejects 150º to the rear”.

For the sake of clarity, I’m going to place the graph of Super Cardioid (left) and Cardioid (right) together:

The rejection of a Super Cardioid microphone is more than a Cardioid Microphone.

As you move from the front (0º) to the sides (90º and 270º) in the Super Cardioid graph, you’ll see a higher decline in sensitivity in comparison to the Cardioid graph.

Also, the rear rejection (180º) is more in Super Cardioid. See how the curve is flat in Super Cardioid but round in Cardioid.

Combine low sensitivity with a narrow polar pattern, you get a Condenser Mic that can be used in live performances as well.

Note: The sensitivity of M2 (6.30 mV) is quite low as compared to NT-1 (35.00 mV) and both are Condenser Microphones. But the sensitivity of M2 (6.30 mV) is still significantly higher than M1 (1.60 mV) and it's a Dynamic Microphone.

Frequency Range vs Frequency Response

Do you know what is the human hearing range? It’s 20 Hz to 20,000 Hz.

As I mentioned before, human ears function the same way as a Microphone so it should also have a defined Frequency Range to pick up, right?

All microphones will this date under their basic specifications. Let’s take the same example of NT-1 and M1:

This is another difference between a Condenser and a Dynamic Microphone (it’s not the case every time though).

More important than the Frequency Range of a Microphone is its Frequency Response. Yes, these are two different things!

A Microphone’s Frequency Response is another graph that has the human hearing range laid out on the X-Axis and sensitivity on the Y-Axis.

Here’s how the Frequency Response of NT1 and M1 look like:

• Characteristics of NT-1: It has an almost flat curve with a subtle dip below 30 Hz and a 2 dB bump in the 4 kHz to 10 kHz range.
• Characteristics of M1: It has a highly colour curve with relative flatness only in the 300 Hz to 1 kHz range.

The best microphone would generally have a flat frequency response.

With that being said, it does not translate to a good sound because that’s where the personal taste of the listener or the engineer comes into perspective and that’s highly subjective. This is if I’m assuming that both the mics are getting used in the same environment.

Getting a flat/uncoloured recording provides us with an option to modify the tone later. If it’s already coloured, then there might be artefacts added to it. Sometimes you can remove them and sometimes they become a huge pain.

Then why is NT1 so coloured? That’s because its primary use is in Live performances.

• The cut below 100 Hz ensures that the low frequency pick up is minimized (that of the Bass Guitar, Kick Drum or Percussions).
• The flat central section ensures that the speech intelligibility range isn’t coloured a lot.
• The bump starting at 3 kHz and going till 12 kHz (approx.) brings out the presence in the voice which is generally overpowered by other instruments.

As advertised, Rode has tried to provide a Live Performance Dynamic Microphone (M1) that has some sort of Pre-Equalization.

Conclusion

• Selecting a Microphone requires in-depth research. I know it’s tedious, but you won’t end up buying a Mic that doesn’t serve your purpose.
• Defining your purpose even before you start looking for a Mic is half the work.
• Ideal graphs do not mean ideal sound. As I said before, it’s subjective.
• Lastly, the best way to buy any audio equipment is by listening to it. If you get a chance to hear how your selected Mic sounds like, do not miss out on that opportunity.

Check out my post on What is Audio Compression – Know Right to Mix Right!