In the following article, we’re going to take a closer look at microphones used for recording acoustic guitar. I’ll also explain how mics work and help clear up any confusion around technical terms such as Dynamic Range and Maximum SPL. So if you’re unsure what microphone to get started with, this article is for you.
Recording Acoustic Guitar on a Budget
Because the choice of mic is so important to the recording process it’s not uncommon for high-quality microphones used in professional recording studios to cost thousands of dollars. These are some of the best microphones for recording available and include brand names such as Sony, Neumann, and Telefunken.
Obviously, without the luxury of a dedicated recording studio and audio engineer, spending this kind of money is impractical.
But, there are some solid offerings in the entry to mid-price range, mostly due to the increasing popularity of independent artists and home recording and a number of decent options available that will get you underway recording acoustic guitar and vocals for less than $100.
I wouldn’t go much lower than $100 though. If you want to produce good audio cheap microphones tend to be fairly hit-and-miss. If you have the budget avoid the lower price points and start at least the $100 mark.
How Microphones Work
If you have ever talked mics with a sound engineer, you know that discussing the various types and how they work can devolve into a fairly detailed technical discussion, pretty quickly. Chances are you will hear strange terms such as cardioid condenser, polar patterns, phantom power, frequency response, and proximity effect and be left more confused than when you started.
We’ll get into some of those terms below but for the sake of keeping things simple, remember microphones are designed to perform one very specific role. Convert sound into an electrical signal.
How a microphone converts sound into an electrical signal is where the real magic happens and that’s the job of the transducer (aka the element) which is found inside the mic’s capsule. A transducer is something that converts one form of energy into another, in the case of the humble microphone it converts sound into electrical energy.
Types of Microphones
When it comes to choosing the right microphone for your needs, there are essentially three main types of microphones to choose from – dynamic, condenser, and ribbon.
There are other types of microphones, but these are less common, and due to the high price for ribbon microphones, the choice normally comes down to condenser or dynamic for home studios.
Dynamic microphones work in much the same way as a speaker, only in reverse. The design, like a speaker utilizes a magnet, a voice coil (the wire coil attached to the back of the diaphragm), and a diaphragm. If you have seen a speaker up close you will have seen a voice coil at the rear of the speaker.
The voice coil and magnet in combination create a magnetic field, much like a guitar pickup does. As sound waves hit the diaphragm, the diaphragm begins to vibrate, which in turn causes the voice call to vibrate. As the voice coil vibrates over the magnet an electrical signal is created and can be measured. This is the branch of physics known as electromagnetism.
Condenser is just another word for a capacitor. If you know anything about capacitors, you know that a capacitor is an electrical component that stores electrical energy (much like a battery) in an electric field between two plates, with one being positive and one negative.
As you may have guessed, a condenser mic, therefore requires a source of electricity, to create that initial electrical field between the two plates. The power used for condenser microphones is typically in the form of phantom power.
The plate at the front of a condenser microphone is light (the diaphragm) and vibrates when hit by sound waves, the vibrations change the distance between the two plates and as a result, the amount of electrical energy stored between the two plates otherwise referred to as capacitance.
More electrical energy is stored as the plates come closer together and less when the distance between them increases.
What is Phantom Power?
Phantom power is used to transfer electricity (DC voltage, usually 48V) through a cable to power a device, in this case a microphone. In times gone by, to use a condenser mic you needed a phantom power supply. But, if you use an audio interface, you may notice a button for phantom power, or it may also say 48V. If not, you will require an external power source, such as the one pictured.
Which microphone is best for recording acoustic guitars in a home studio?
Now that we have a basic understanding of how these two microphones work, which is the best for recording acoustic guitar in a home studio environment?
Condenser microphones, but both have their uses.
Dynamic microphones, due to the method used to convert sound into an electrical signal tend to handle high levels of volume (e.g. without distorting) extremely well.
They are typically more robust than condenser microphones, due to the mass of the magnet used to create the magnetic field that powers them. Because of this, they are best used in close proximity to the input source, making them a good option for micing guitar amps, drum kits, and vocals in a live setting.
The Shure SM57, perhaps the most well-known live performance microphone is a dynamic microphone.
Condenser microphones, on the other hand, have a higher frequency response than dynamic microphones. Frequency response refers to how accurately the signal response is in relation to the input source e.g. the sound being picked up by the microphone.
Condenser microphones are more sensitive because they are lighter in design e.g. they don’t utilize a heavy magnet to create a magnetic field like a dynamic microphone. This means the plates require less energy to move, in the case of a condenser mic this means they respond to more subtle frequencies and detect a wider range of frequencies more accurately. They also tend to handle transients more effectively.
What is a transient?
Transients are the high amplitude, short bursts of energy at the start of a sound wave. They represent the impact of the sound wave and last just a few milliseconds. Condenser microphones are more sensitive to transients, while dynamic microphones tend to be less sensitive to transients which can actually be a useful thing if micing up drums for instance.
Because of this, condenser microphones are usually the preferred option in the studio for stringed instruments, as they allow for greater detail, which makes them particularly well suited to the acoustic guitar.
Because of this, if you are buying just one microphone, choose a condenser microphone.
However, keep in mind, both types of microphones have their place. In my experience, there have been times when a dynamic microphone, for one reason or another, has been a better fit for a particular song, so it’s useful to have both on hand.
Large and small diaphragm condenser microphones
If you are buying a condenser microphone, the next decision you will need to make is whether to buy a large or small diaphragm condenser microphone.
The difference between large and small diaphragm condenser mics mostly comes down to the size and mass of the diaphragm.
While this is obvious in a visual sense, with the larger diaphragm microphone being the more iconic ‘studio mic’, the differences in responsiveness and sensitivity have an influence over the frequency response of the mic.
While condenser microphones have a higher frequency response than dynamic microphones, due to the greater mass of the larger diaphragm condenser mic the frequency response is not as fast as a small diaphragm condenser mic.
This means smaller diaphragm mics are more responsive and offer greater sensitivity. This typically results in a more accurate sound.
A large diaphragm condenser microphone on the other hand is often described as having a warmer sound and may add more presence to the sound of an acoustic guitar.
In a practical sense, while the small diaphragm microphone will provide a little more detail, it is more directional and you are more likely to pick up some of the finer details as well, such as string noise, which you may or may not want on your recording. Typically, when recording vocals, a small diaphragm mic captures too much detail and will tend to sound a little too bright.
The choice really does come back to your own preferences, and the sound of the guitar you are using. e.g. if your guitar sounds overly bright, a large-diaphragm microphone may balance the tone out a little more effectively. Alternatively, if you have a great-sounding guitar with a rich tone and the guitarist plays fingerstyle and has a more delicate approach a smaller diaphragm microphone will accentuate some of these qualities more effectively.
As we are focusing on the home studio owner’s first mic in this article, if choosing between the two, all things being equal a large-diaphragm microphone is a better all-rounder for the humble home studio and will do a good job of both the acoustic guitar and vocals. But, it can also be a good idea to have both if your budget allows it as you will have more options up your sleeve.
Microphone Polar Patterns
When looking over the specs for different microphones you are going to come across the term polar patterns, and the different types including omnidirectional, cardioid, super-cardioid, and bi-directional, among others.
Microphone polar patterns refer to the microphones’ directional sensitivity. e.g. how effectively the microphone detects (and just as importantly ignores) sound from specific directions.
As you can imagine, the ideal microphone polar pattern can be dependent on other aspects of the recording such as the acoustic properties of the room, and microphone placement and proximity.
I’ve covered microphone polar patterns in an article here, but I have summarized the four main polar patterns you are likely to come across below.
Omnidirectional: The microphone detects sound equally from all directions, including detecting ambient room sound
Cardioid: Detects sound waves mostly from the front.
Super-Cardioid: Generally a more tightly focused sensitivity to the front of the microphone. Super-cardioid microphones also detect some sound from behind the microphone.
Bi-directional microphones: Detect sound in a figure 8 pattern.
Which polar pattern is best for recording acoustic guitars?
There really is no right or wrong answer, as it depends on a number of different variables.
For example, you may be thinking a cardioid microphone is the better option for recording a more detailed recording of the acoustic guitar (and in the majority of cases it is the most common). But in some cases, they are less than ideal if the mic is very close to the guitar, due to the proximity effect, which means the closer a source of sound comes to a ‘directional’ microphone the greater accentuation of bass frequencies.
This means to use a directional microphone you need to achieve a balance between microphone proximity and the polar pattern of the microphone to achieve a great-sounding recording.
Alternatively, omnidirectional microphones (due to capturing a lot of ambient sounds) tend to work well as a secondary ‘room mic’ for recording acoustic guitars or as the main microphone if the room sounds particularly good.
Alternatively, depending on your recording environment, a super-cardioid microphone (due to detecting sound from the rear also) may be less than ideal in noisier environments.
And lastly, if you are using two microphones, in some circumstances bi-directional microphones can also work well.
If all this sounds confusing, don’t overthink it, go for a cardioid microphone, or if your budget extends that far choose a multi-polar pattern condenser microphone such as the Rode NT2A or Audio-Technica AT4050.
What about USB microphones?
There’s no doubt that USB microphones are a convenient option, especially if you don’t use an audio interface. But they are more prone to latency issues as USB microphones need to convert the analog signal to digital before it can be read by the computer. This often can result in a slight delay (latency).
If using a standard microphone into an audio interface the conversion is handled by the audio interface.
USB microphones also limit your recording to one input, which may be fine when just getting started but is far from ideal if you want to expand upon things in the future as you would need to start over with an audio interface and microphone.
While they are convenient and by all accounts improving all the time, if recording music you are best advised to avoid them, at least for the time being.
Should you use a Pop Filter when recording acoustic guitar?
No, pop filters are used specifically for reducing plosives and sibilance when recording vocals. For those unaware, plosives are the explosive sounds that occur when a vocalist uses a word beginning with B, P or T. Sibilance occurs when the vocalist uses words that begin with S or T, resulting in a hissing sound.
Acoustic guitars do not produce these sounds so a pop filter is not required.
The Best Microphone for Recording on Smartphone?
You may be surprised, but the microphone on the majority of smartphones is a lot better than most people realize, not to mention many current smartphones have two internal microphones.
If you are recording a quick song idea on the voice memo app on your iPhone for example, the quality of the internal speaker can be genuinely surprising.
But, if you plan on doing something a little more sophisticated e.g. recording tracks to a dedicated DAW app such as Garageband, using a dedicated microphone can offer a cleaner recording experience and can also be more convenient with regard to microphone placement.
In the case of the iPhone, the internal microphone is omnidirectional, so it’s not as targeted and therefore has the capacity to detect unwanted noise from the back and sides.
Using an external microphone offers more control but you can’t just plug a regular microphone into a smartphone due to the input connection size or type (e.g. iPhones use a lightning port) and the fact that you generally require a TRRS cable.
A TRRS cable includes both the left and right channels along with a microphone channel, as smartphones typically use one input for both input and output.
In the image below the TRRS cable is shown on the left. Notice the three bands as opposed to two on the right-hand side cable?
I have written a complete article on recording with a smartphone and based on my own experience my recommendation is to purchase a Rode VideoMic Me.
I use one of these fairly regularly and while they aren’t as loud as the internal microphone on a standard smartphone they do offer a cleaner recording experience. The microphone itself is a 1/2″ condenser microphone and is more directional than the internal mic on the iPhone, allowing you to target specific areas on the guitar such as the standard 12th fret mic placement.
Understanding Microphone Technical Specifications
Finally, to round out this article on how to choose the best mic for acoustic guitar I’m going to list out some of the technical terms you might notice when looking into the different types of microphones.
- Diaphragm size: The size of the mics’ diaphragm
- Acoustic Principle: The type of transducer used
- Directional Pattern: Just another word for ‘polar pattern’
- Frequency Response: The accuracy of the signal response is in relation to the input
- Output Impedance: The measure of resistance to the electrical signal
- Sensitivity: A measure of how well the mic converts sound energy into electrical energy.
- Equivalent Noise: The amount of sound pressure required to create the same voltage as the mic produces
- Dynamic Range: The pressure range that exists between the lowest and highest level the microphone can handle
- Maximum SPL: The maximum output achievable before the onset of clipping or distortion
- Signal/Noise: Signal-to-noise ratio. The level of signal compared to the level of background noise.
- Power Requirements: The voltage required for the microphone to operate
Quick Tips for Getting the Best out of your Microphone when recording Acoustic Guitar
- Pointing the microphone between the 12th and 14th fret of the guitar (most common microphone placement for recording acoustic guitars).
- Keep the microphone at least 12 inches from the guitar. (Avoid positioning the mic closer).
- Record with a microphone, not a direct line. Your microphone will almost always sound better than your acoustic pickup.
- Never point the microphone directly at the soundhole. This will prevent excessive low-end frequencies.
- Record in mono if using one microphone.
- Keep condenser microphones away from moisture (when stored, control the humidity).
- Keep in mind condensers are sensitive mics and are more easily damaged than dynamic mics. Handle with care.
- Maintain your gain levels between 50% — 70%.
If you are just getting into home recording and plan on recording acoustic guitar and perhaps vocals, to begin with, it’s more practical to select a solid ‘all-rounder’ that can handle all your requirements. In the majority of cases, this will be a large-diaphragm condenser microphone.
For those with a little more to spend, consider both a large diaphragm and small diaphragm model, before adding a dynamic microphone to your arsenal.