Can a mic be stereo?

What is a Stereo Mic?

Stereo is a method of recording, reproducing, or broadcasting sound so that the impression of sound direction and sound source distance is preserved. Regular microphones capture audio in mono, which means the sound is recorded into a single audio channel. This results in an audio recording that does not convey spatial positioning or directionality of sounds.

In contrast, stereo microphones have two microphone capsules or elements arranged closely together in the same enclosure. Each capsule records sound independently, and the two audio signals are kept separate in left and right channels. When played back properly in stereo, this setup allows preserved spatial imaging and directionality of sounds, providing a wider and more realistic representation of the soundscape.

So in summary, stereo microphones capture audio in true left and right channels, allowing for a realistic soundstage, unlike regular mono microphones which collapse audio into a single channel.

How Stereo Mics Work

Stereo mics use two microphone capsules or elements to capture a wider, more three-dimensional sound image than a mono mic can. There are a few common stereo mic techniques that work in slightly different ways:

Mid-Side (M-S) stereo mics have one mic pointed forward (the Mid mic) to pick up what’s directly in front of it, and one mic pointed sideways (the Side mic) to capture a broader field. The mid mic captures direct sound while the side mic captures ambient sound from the sides. During processing, the mid and side signals are matrixed together to produce a stereo left and right channel.[1]

X-Y stereo mics have two matched mic capsules angled apart at anywhere from 90 to 135 degrees. Each capsule picks up a slightly different part of the sound field. The angle between the capsules determines the width of the stereo image. A wider angle gives a more spacious stereo effect.[2]

Spaced omnidirectional mics use two omnidirectional mics placed some distance apart to capture subtle timing and sound pressure differences between the mics. Greater spacing increases the stereo effect. Spaced omnis can provide a very natural stereo image.[3]

Stereo Mic Patterns

Stereo microphones use various polar patterns to capture the stereo image. The most common patterns are cardioid, hypercardioid, omnidirectional, and figure-8 or bidirectional. These patterns allow the mic to pick up sounds from different directions and create a stereo effect.

Cardioid mics pick up sound from in front of the mic capsule, while rejecting sound from the sides and rear. This focused pickup allows for isolation of sound sources. Cardioid mics are often used as the left and right capsules in a stereo mic setup (Source).

Hypercardioid mics have a tighter pickup pattern than regular cardioids, further narrowing in from the sides for a more direct front pickup. This helps minimize bleed from other sound sources. Hypercardioids provide more separation between the left and right channels in a stereo mic.

Omnidirectional mics pick up sound equally from all directions. This wide, spherical pickup can give a spaciousness and room ambience to the stereo image. Omnis are sometimes used as one capsule next to a directional mic in a stereo configuration.

Figure-8 or bidirectional mics pick up sound from the front and rear, while rejecting sound from the sides. The polar pattern is two-lobed, resembling the number 8. Bidirectionals can create a rich stereo image with front and rear sound pickup.

Using multiple pickup patterns gives stereo mics a complex soundstage with directional and ambient information. The polar patterns essentially divide the soundfield to preserve spatial relationships in the stereo image (Source).

Using Stereo Mics

When using stereo mics, proper placement and technique are essential to capturing the full stereo image. For vocalists, the widely accepted method is an X-Y pattern with the two capsule heads angled between 90-110 degrees. This provides clear stereo separation of the vocal while maintaining phase coherence. Place the mic six inches from the singer’s mouth, angled upwards towards the forehead ¹.

For acoustic instruments like guitar or piano, try the ORTF technique with capsules spaced 17cm apart, angled at 110 degrees. Point the mic towards the instrument’s soundhole from one to two meters away. For drums, use a stereo overhead in a Blumlein pattern to capture cymbals and toms. For ambient room sound, space two omni mics apart and experiment with different polar patterns like XY or ORTF ¹.

Getting optimal stereo separation involves both mic placement and the listening environment. Wider spacing yields more pronounced stereo effects. Close attention to phase coherence avoids collapsed imaging. Listening on stereo speakers or headphones reveals the full stereo picture.

Stereo Mic Applications

Stereo microphones are popularly used in various audio recording applications to capture a realistic stereo image with natural spatial characteristics. Some common applications of stereo mics include:

Music Recording – Stereo mics are widely used to record instruments, vocals, and live performances in music production. They capture the subtle nuances, textures and ambient details essential for professional music recording.

Film Production & Post Production – Stereo mics enable capturing realistic ambience and spatial depth for film dialog, sound effects, and Foley work. They are often used to record ambient backgrounds and spot effects.

Podcasting & Voice Over – Podcasters often use compact stereo USB microphones to conveniently record interviews, co-hosts and ambient sound for an engaging, immersive listening experience.

ASMR & Binaural Recording – Special binaural stereo mics are used to create 3D, immersive audio recordings of ambient sounds. The Sony Nex 5t has a stereo microphone used for indoor talking head videos for YouTube with some product B-roll and photography on treks and trails.

Stereo Mic Specifications

Some important specifications to consider when choosing a stereo microphone include frequency response, sensitivity, and signal-to-noise ratio (SNR).

The frequency response indicates the range of frequencies the microphone can pick up. For high-quality audio reproduction, a wider frequency range like 20Hz – 20kHz is ideal (Podcasting Omni Stereo Microphone Specifications). Sensitivity measures how well the mic converts acoustic energy into electrical signals, rated in decibels. Higher sensitivity mics around -35dB are more effective at capturing subtler sounds.

SNR compares the level of the desired audio signal to unwanted noise in the recording. A higher SNR (greater than 70dB) results in clearer audio. So when comparing stereo mics, look for wide frequency response (20Hz – 20kHz), high sensitivity (-35dB or lower), and high SNR (70dB or greater).

In terms of pricing, stereo condenser mics range from around $100 for basic portable models up to $1000 or more for professional studio mics. Consider your budget and intended application when deciding.

Choosing a Stereo Mic

When selecting a stereo microphone, there are a few key factors to consider:

Budget – Stereo mics range greatly in price from under $100 to over $1000. Determine how much you want to invest based on your needs. If you’re just starting out, an entry-level XYX mic around $200 may suffice. For pro studios, spending more on a high-end ABC model ensures excellent sound quality.

Use Case – Will you use the stereo mic primarily for studio recording, field recording, live performances, or a combination? Studio mics like the XYZ condenser are optimized for vocals and acoustic instruments. For outdoor ambience, a portable PQR shotgun mic works well. Know your application to choose the right mic type.

Sound Quality – Stereo mics aim to capture a realistic, immersive soundscape. Key factors are frequency response (how evenly it picks up lows, mids, highs), sensitivity (signal-to-noise ratio), and low self-noise. High-end mics perform best in these areas. Listen to samples to determine audio quality needed.

Additionally, consider stereo mic patterns, connectivity, form factor and accessories. Understanding how you plan to use the stereo mic will ensure you select the right model for your budget and needs.

Setting Up A Stereo Microphone

When setting up a stereo microphone, proper mic placement is crucial for capturing a realistic and natural stereo image. The first fundamental stereo microphone technique is known as the XY technique, where the two mic capsules are at an angle of anywhere from 45° to 180°, depending on the desired stereo width and separation. For more information on the history of the XY technique, refer to this article.

Other popular stereo miking setups involve spaced omnidirectional mics (AB technique) or angled cardioid mics (ORTF technique), with varying degrees of spacing and angling to achieve the desired stereo image. Some key considerations when placing stereo mics include:

• Angling the capsules appropriately for the stereo technique
• Positioning the mic at an appropriate distance from the sound source
• Pointing the capsules directly at the sound source
• Mounting the mic securely to minimize vibration and handling noise

Accessories like stereo bars and mounts can help optimally set up and position stereo mics. Wind protection is also important for reducing unwanted rumble when recording outdoors. With attention to proper panning, level matching, and post processing, a well-positioned stereo mic setup can capture a beautifully realistic stereo image.

Stereo Mic Examples

Some popular stereo microphone models include:

• Rode NT4 – A compact stereo condenser microphone good for recording instruments, choirs, and outdoor ambience (https://ehomerecordingstudio.com/stereo-microphones/). The NT4 provides excellent sound quality at an affordable price point.
• Audio Technica AT2022 – An X/Y stereo condenser mic ideal for podcasts, vocals, acoustic guitars, and drum overheads (https://ehomerecordingstudio.com/stereo-microphones/). The AT2022 delivers clear, natural stereo imaging.
• Blue Yeti – A USB stereo condenser mic designed for podcasting, game streaming, vocals, and music recording (https://ehomerecordingstudio.com/stereo-microphones/). The Yeti offers simplified stereo recording without needing an audio interface.

The Rode NT4 is known for its clear stereo imaging and rugged metal construction. However, it requires 48V phantom power and outputs at line level, so an audio interface is needed. The AT2022 runs on battery or plug-in power and has a camera shoe mount, but lacks the premium build quality of the NT4. The Blue Yeti excels at quick stereo recording direct to a computer, but sound quality falls short of XLR condenser mics.

The Future of Stereo Mics

Stereo mics continue to advance along with other audio technologies. Some emerging innovations in stereo mic design include digital modeling, wireless connectivity, and integration of artificial intelligence (AI).

Digital modeling allows stereo mics to emulate different mic patterns and sounds virtually. This provides more flexibility and can reduce the need for multiple physical mics. Mics may also increasingly incorporate wireless capabilities for easier remote recording and mobility.

AI is being researched to enable smart processing and mixing capabilities in stereo mics themselves. This could allow mics to automatically adjust their settings and processing based on the recording environment. It may also enable advanced features like source separation.

As these technologies progress, stereo mics are likely to become more versatile, intelligent, and integrated into wireless production workflows. The future possibilities are exciting for capturing immersive, three-dimensional recordings. While the fundamentals remain important, innovations in digital processing, connectivity, and AI will unlock new creative potential.