Microphones are used extensively in today’s music, television, radio, and other media. The vast majority of recorded music today is in stereo but the voice in many voice-centric recordings (podcasts, vlogs, etc.) is often mono (if but only panned centre in a stereo mix).
Do microphones output mono or stereo signals? Microphones convert sound waves to audio signals via mic capsules. Most mics have one capsule that outputs one signal, making them mono devices. Some mics have multiple capsules and output multiple mono signals (which could be mixed in stereo). However, “stereo mics” are truly multiple-mono devices.
So microphones and microphone signals are really only ever mono, but there are such things as stereo microphones and even ambisonic and surround sound microphones. Let’s discuss these microphones in more detail along with mono and stereo audio.
Microphones Output Mono Signals. Stereo Microphones Output Multiple Mono Signals.
So we know the amount of individual mic signals that one microphone is capable of outputting is equal to the number of [activated] capsules. Stereo microphones have at least two capsules and each capsule outputs its own mic signal. It’s up to the mixer to pan these mic signals if the microphone’s outputs will ultimately be stereo or not.
That being said, stereo mics are fully capable of acting as mono microphones if only one capsule is recorded/used (or if the two signals are not panned in the stereo mix). On the flip side, multiple “mono microphones” are often positioned stereo miking techniques, where each mic signal is later mixed in stereo.
The basic idea of a stereo microphone, then, is to have a single unit that houses a coincident pair of microphones by having two separate mic capsules within a single microphone body.
Stereo Miking Techniques
Stereo miking is a form of “true stereo” where two or more mono microphones (or one or more stereo microphones) are positioned to capture a stereo image of an acoustic space. The mic signals are then panned according to their position in a stereo mix.
Stereo miking techniques are the set positions and/or principles behind stereo miking. Most stereo miking techniques keep things simple with a two mic setup with one mic panned left and then other panned right. Of course, a single stereo mic works similarly to a stereo technique where two capsules are positioned very close to one another.
As mentioned, stereo miking techniques can have more than two mic capsules in their array but a simple pair will provide a stereo image. The three general types of stereo pairs are:
- Coincident pair: A coincident pair of microphones is made of two of the same mic positioned together in such a way that sound waves arrive at them at [practically] the same time. Stereo microphones are really a coincident pair of mic capsules in the same microphone body.
- Near-coincident pair: A near-coincident pair is a pair of microphones spaced roughly 6-12 inches apart and angled symmetrically on either side of a centre axis. Near-coincident pairs are often preferred for their stereo image since the mic positions somewhat simulate human ears.
- Spaced pair: A spaced pair is two identical microphones that are separated by several feet (usually one-third to one-half the width of a sound stage) and point directly at a sound source. Spaced pairs yield wide stereo images but typically have poor mono compatibility.
To learn more about stereo pairs, check out the following My New Microphone articles:
• Top 8 Best Stereo Miking Techniques (With Recommended Mics).
• What Is A Coincident Pair Of Microphones? (With 2 Techniques).
• What Is A Near-Coincident Pair Of Microphones? (+7 Examples).
• What Is A Spaced Pair Of Microphones? (With 3 Techniques).
As we can see, stereo microphones are excellent at providing a coincident pair but it would awkward to build a single microphone with near-coincident of spaced mic capsules. For this reason, single capsule “mono” microphones are often preferred in studio environments.
Working With Stereo Microphones
Now that we understand what a stereo microphone is and what it can do for us, let’s discuss working with stereo microphones.
First, I’ll reiterate that stereo mics are really multiple-mono microphones. It’s easy to tell by looking at the microphone output connection. Stereo microphone outputs are most often of the 5-pin XLR variety.
Let’s break down a 5-pin XLR pin by pin to understand a stereo mic’s output:
- Pin 1: Common ground/shield.
- Pin 2: Mic capsule A signal in positive polarity.
- Pin 3: Mic capsule A signal in negative polarity.
- Pin 4: Mic capsule B signal in postive polarity.
- Pin 5: Mic capsule B signal in negative polarity.
Basically this means there are two balanced audio signals with a common ground. Stereo microphones with the standard 5-pin XLR connector will come with a 5-pin XLR to dual 3-pin XLRs adapter so that each mic capsule signal can be sent through to a mic preamp.
To learn more about microphones and XLR connections, check out my article Why Do Microphones Use XLR Cables?
Each of the mic capsule signals is amplified by the preamp and sent through to the mixing console, recording device or DAW, where the signals should be panned according to the stereo mic’s design.
To get the most out of a stereo mic, we must know the type of coincident pair its capsules are arranged in.
There are basically three coincident pair arrangements for stereo microphone capsules:
- XY stereo microphone: XY stereo microphones have two cardioid-type capsules (cardioid, supercardioid, or hypercardioid) that point 90° to 120° from one another. In the mix, the capsule that points left is panned left while the capsule that points right is panned right.
- Example of an XY stereo mic: Schoeps CMXY 4V (link to check the price at B&H Photo/Video).
Schoeps is featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
- Blumlein stereo microphone: Blumlein stereo microphones have two bidirectional (figure-8) mic capsules stacked one on top of the other and angled at 90° from one another. These stereo mics point straight up when in position. When facing an intended sound source (on-axis), each capsule should point 45° off-axis either way. The positive polarity of the bidirectional polar patterns face forward. In the mix, the capsule that points left is panned left while the capsule that points right is panned right.
- Example of a Blumlein stereo mic: Royer Labs SF-12 (link to check the price at B&H Photo/Video).
Royer is featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
- Mid-side stereo microphone: Mid-side stereo microphones are designed with one cardioid-type capsule facing 0° (on-axis) and one bidirectional (figure-8) capsule pointing at 90° and 270°. These stereo mics point straight up when in position and have the cardioid capsule face the intended sound source. In the mix, the cardioid capsule’s signal is panned in the middle (mid/mono). The bidirectional capsule’s signal is duplicated with one signal panned hard left and the other panned hard right with the phase inverted.
- Example of a mid-side stereo mic: Sanken CMS-2
Of course, we could (and have for a long time) use two independent microphones to achieve any of the above near-coincident stereo miking techniques. The main benefit of using stereo mics instead is that they are easy to use and already setup perfectly according to their design.
Stereo USB Microphones
So we’ve discussed how stereo microphones really output multiple mono analog signals. In doing so, we’ve left out “digital” USB microphones. These types of microphones have been and continue to gain popularity and should be talked about here.
The whole idea of a “digital microphone” or USB mic is to have the analog-to-digital convert inside the mic rather than in the mixing console or audio interface. This allows us to connect USB mics directly into our computers and have them work.
For more information on analog and digital microphones, check out my article Are Microphones Analog Or Digital Devices? (Mic Output Designs).
So the question is: can digital USB microphones output stereo data? The answer is yes!
Stereo USB microphones are designed so that both mic capsules run through the analog-to-digital converter and are outputted as stereo digital audio data. This works similarly to having two individual microphones setup in a stereo miking technique, having each of them run through a single audio interface (ADC), and then having them panned in a mixing console or DAW. The main difference here is that the stereo USB mic can record directly to a stereo track without the need for pan adjustments in the mix.
The most popular stereo USB microphones on the market is the Blue Yeti (link to check the price on Amazon). When this multi-pattern mic is set to stereo mode, it engages its two stereo mic capsules that are set in an XY arrangement. The Blue Yeti outputs stereo digital audio data from its USB output that can be captured directly inside a computer’s digital audio workstation.
Blue is also featured in My New Microphone’s Top 11 Best Microphone Brands You Should Know And Use.
What Are Ambisonic Microphones?
Thus far we’ve only been speaking of mono and stereo audio. However, there are many other mixing/playback formats on the market including surround sound and ambisonics. Are there microphones for these formats?
Indeed there are! Let’s talk about ambisonic microphones.
What is an ambisonic microphone? An ambisonic microphone is a single mic designed to capture sound in a full-sphere surround sound format. Ambisonic mics often include 4-8 capsules (or more) in order to output sound for 3D ambisonic mixing with mic-specific software.
Note that even with ambisonic microphones, each mic capsule outputs its own mic signal, each of which is sent to its individual channel. These raw mic signals are inherently mono and are referred to as A-format ambisonics.
It is only in the mix and playback that the combined signals yield a truly ambisonic sound. Specialty mixing software (which is often microphone specific) is used to position each of these channels properly for an ambisonic mix and playback.
A great example of an ambisonic microphone is the Core Sound OctoMic. This microphone features 8 individual mic capsules evenly spaced in a 3D array. The OctoMic’s signals can be converted from A-format to B-format with the VVOctoEncode VST plugin or the Octofile (for Linux users).
Are shotgun microphones mono or stereo? Shotgun mics are mono microphones. These highly directional mics have one capsule at the end of their long interference tubes and output one mono mic signal. The confusion as to whether shotgun mics are mono or stereo may come from the many sound ports in the interference tube design.
To learn more about shotgun microphones, check out the following My New Microphone articles:
• The Lobar/Shotgun Microphone Polar Pattern (With Mic Examples).
• Best Boom Microphones For Film.
• Best Shotgun Microphones For A Camera.
Should voice be recorded in mono or stereo? Recording the human voice (singing, dialogue, narration, etc.) is practically always better in mono. Recording in mono makes the voice more present (no phase cancellation, equal volume in both stereo channels). This is ideal since the voice is practically always the most critical component of a mix.