Microphones

Everything you need to know.

The invention of the microphone dates back to 1876 by Emile Berliner and was initially used in telecommunications. It is a device that converts sound waves into electrical signals. Essentially, it is used for amplifying, recording, or transmitting sound. When we speak or play a musical instrument in front of a microphone, sound waves are generated, causing vibrations in a sensitive diaphragm located inside the microphone. These vibrations are converted into an electrical signal, which can then be amplified, recorded, or transmitted.

In summary, during the early 20th century, carbon microphones dominated, while in the 1920s, the first condenser microphone was developed by Edward C. Wente, offering better sound quality. Subsequently, in the 1930s, dynamic microphones emerged, providing greater durability, and in the 1940s, Ribbon microphones, such as the RCA 44, appeared, offering a more natural sound for recordings. From the 1960s onwards, electrostatic and digital microphones contributed to the advancement of sound, making microphones essential for both studio recordings and everyday use.

Choosing the right microphone is critical for achieving the best possible sound quality, whether it's for music recording, podcasting, or live performances. Microphones vary in terms of technology, usage, and performance, so understanding their key features will help you make the best choice.

So, let's take a look at the types of microphones.

Condenser microphones

Condenser microphones cover the entire range from inexpensive to very high-quality models. They are now the most classic and popular microphones for any studio use. They require a power source, which is provided either through the microphone input as phantom power or via a battery. This is necessary to supply the operating voltage but also for the internal signal amplification to achieve the required output. Condenser microphones are also available with two diaphragms, which are combined in such a way as to provide a range of polar patterns, such as cardioid, omnidirectional, hypercardioid, etc.

• Advantages: They have high sensitivity, a wide frequency range, and are ideal for studio recordings.

• Disadvantages: They require phantom power (48V), are more sensitive to environmental noise, and are ideal for vocals, acoustic instruments, pianos, and studio recordings.

Dynamic microphones

Dynamic microphones are a type of microphone that uses a magnet and a coil to convert sound waves into electrical signals. They are durable, reliable, and less sensitive to external noise, making them ideal for live performances and environments with high sound levels. Unlike condenser microphones, they do not require external power and can handle loud sounds without distortion. They are often used for guitar amplifiers, vocals in live performances, and drums, due to their robustness and ability to deliver clear sound in intense conditions.

• Advantages: Durability and long lifespan, do not require phantom power, and are better suited for live performances.

• Disadvantages: They have lower sensitivity than condenser microphones, do not perform well with details in high frequencies, and are considered ideal for live performances, drums, guitar amplifiers, and loud sounds.

Ribbon Microphones

Ribbon microphones are a type of microphone that uses a thin metal ribbon as a diaphragm to convert sound waves into electrical signals. They are known for delivering a natural and warm sound, as well as for their ability to capture details from different directions due to their bidirectional (figure-8) design. These microphones are sensitive and require careful handling, but they are ideal for studio recordings, especially for vocals, string instruments, and amplifiers. One of their characteristics is that they are not very durable with loud sounds, and they need careful handling.

• Advantages: They offer excellent performance with natural sounds and are ideal for rich, "warm" tones. • Disadvantages: They are very sensitive and prone to damage, often requiring external power or pre-amplification. • Ideal for: Recording vocals, string instruments, orchestral music.

Piezoelectric microphones

Piezoelectric microphones use the piezoelectric effect to convert vibrations into electrical signals. They are ideal for detecting sounds from solid surfaces, as they capture vibrations directly from the source, rather than sound waves in the air. They are often used in acoustic instruments, such as guitars and violins, or in applications where direct contact with the sound source is crucial. They are highly durable and reliable but do not perform as well in high frequencies compared to other types of microphones.

If this does not happen, the frequency response will not be within specifications, and distortions, especially at high levels, will increase. Typically, microphone and preamp connections do not face compatibility issues due to input impedance, as the specifications are designed to ensure compatibility across a wide range of microphones and preamps. The only exception that requires special attention is ribbon microphones, which need both higher signal gain and different input impedance matching. For this reason, there are preamps with special settings for ribbon microphones.

Microphone Measurements and Specifications

Due to differences in their construction, microphones have specific characteristics that define their sound. Frequency response shows the microphone's sensitivity in decibels over a range of frequencies (typically 0–20 kHz). Ideally, a microphone would have the same sensitivity across all frequencies when capturing sound on-axis, meaning at a 0-degree angle to the diaphragm. Maximum SPL refers to the highest sound pressure level a microphone can handle for a given harmonic distortion (typically 0.5% THD). Generally, this harmonic distortion is not audible, allowing the microphone to safely record at such peak levels, e.g., 135 dB SPL (0.5% THD). The dynamic range of a microphone is the difference in SPL between the noise floor and the maximum SPL. Sensitivity indicates how well the microphone converts acoustic pressure into an audio signal. A more sensitive microphone requires less amplification to produce a higher output. While not an absolute measure, sensitivity is often an indicator of a microphone’s quality.

Polar patterns (microphone polar responses)

Microphones come with various polar patterns, which determine the direction from which the microphone picks up sound:

Omnidirectional microphones capture sound equally from all directions, without favoring a specific axis. This makes them ideal for capturing natural, ambient sound or in situations where sound comes from multiple sources simultaneously. They are often used in applications like room recordings, orchestral music, or interviews with multiple participants. While they do not reject external noise as effectively as directional microphones, they perform excellently when a more open, natural sound is required.

Cardioid microphones have a polar pattern that primarily captures sound from the front, rejecting sounds from the sides and rear. This makes them ideal for recordings in environments with unwanted noise, as they focus on the sound source in front of them. They are widely used in vocal studio recordings, live performances, and instrument recordings, where isolating the sound source is important for a clean result. They offer a good balance between sound isolation and natural sound reproduction.

Supercardioid microphones have a polar pattern with an even greater focus on sound from the front compared to cardioid microphones, with reduced sensitivity to sounds from the sides. Although they capture a small amount of sound from the rear, their increased directionality makes them ideal for applications requiring excellent isolation from ambient noise, such as stage recordings or recordings in noisy environments. They are widely used in live performances and recordings where precision and focus on the sound source are essential.

Figure-of-eight microphones (bidirectional) capture sound equally from the front and rear, while rejecting sounds from the sides. This unique feature makes them ideal for situations where sound needs to be captured from two opposite sources, such as in interviews or instrument recordings in the studio. They are often used in stereo recordings or in cases where precise control over the ambient sound is required, offering excellent side noise rejection.

Shotgun microphones have an extremely directional design, with a narrow polar pattern that focuses primarily on sound from the front while rejecting almost all sounds from the sides and rear. They are often used in film, television production, and live events where sound needs to be captured from a distance while isolating unwanted ambient noise. Shotgun microphones are ideal for use in outdoor shoots or situations where precise focus on the sound source is needed.

USB microphones are equipped with a built-in preamp and A/D (analog-to-digital) converter, allowing them to connect directly to computers via a USB port without the need for an external sound card. They are easy to use and ideal for podcasting, voice recordings, streaming, and video calls. USB microphones offer good sound quality at an affordable price and are particularly popular with users who need a quick and simple solution for recording sound without complex setups.

Measurement microphones are specifically designed to capture sounds with absolute accuracy across the entire frequency spectrum, without adding color or distortion to the sound. They are primarily used for acoustic measurements, such as analyzing a room’s frequency response or measuring noise, often in combination with specialized software. Characterized by their omnidirectional sound capture and high sensitivity, they are essential tools for professionals in acoustics and sound engineering.

See all the microphones here

Recording Techniques

There are many microphone recording techniques that aim to ideally capture a musical event. These depend on the available microphones, the recording space, and how we want to capture the music (up close, from a distance, with a large sense of space, with some harmonics more prominent, and many other parameters). The biggest challenge is placing the microphone in a spot where the sound is already narrow and harsh.

For this reason, close one ear and listen to the sound with the other, positioned where the microphone is placed, without the psychoacoustic enhancements you get when listening with both ears. Move the microphone to where the musical instrument sounds best, with a rich and full tone that includes all the harmonics.

Coincident Pair Techniques:

Two microphones placed one above the other, so that the sound waves reach both capsules simultaneously. Coincident Pair techniques include:

XY – Two cardioid microphones at 90 degrees.

MS (Mid/Side) – One microphone, which can range from omni to supercardioid, positioned to face forward (mid) and one figure-eight microphone that captures the sides.

Blumlein – Coincident figure-eight microphones at 90 degrees.

Semi-coincident – Two microphones positioned at an angle to each other to capture the sound stage, spaced between 6 and 48 inches apart. This spacing introduces time-of-arrival and phase differences, in addition to the amplitude differences caused by the directional pattern of the microphones.

Semi-coincident Pair Techniques:

ORTF – A technique originally used in French radio, involving two cardioid microphones positioned at a 110-degree angle, with a 170 mm distance between them.
NOS (Nederlandsche Omroep Stichting) – Two cardioid microphones positioned at a 90-degree angle, with a distance of 300 mm between them.
AB – Two spaced cardioid microphones positioned facing forward, slightly angled toward each other.

Spaced Omnis Techniques:

These techniques are primarily used in classical music recordings, often in combination with close spot microphones. In this setup, two omnidirectional microphones are either mounted on a bar or placed on tall stands, positioned 2 to 3 meters from the front of the orchestra. This approach captures a wide and natural sound, ideal for large ensembles like orchestras.

Important factors for choosing a microphone

A. Usage

• Studio Recordings: Choose condenser microphones for clear and detailed sound.

• Live Performances: Dynamic microphones are more suitable due to their durability.

• Podcasting: A condenser or USB microphone is an excellent choice for capturing clean and natural sound.

B. Phantom Power

If you choose a condenser microphone, ensure that your audio interface or preamp supports phantom power (48V).

C. Budget

Microphones come in a wide range of prices, so it's important to set a budget according to your needs and intended use.

Tips for a new purchase

• Test before buying: If possible, try the microphone before purchasing to see how it performs in your space.

• Pay attention to the pickup pattern: Make sure the microphone you purchase has the correct polar pattern for your application.

• Invest in quality: A good microphone can last for years. Invest in a microphone that will meet your needs in the long term.

The choice of the right microphone depends on your needs, budget, and intended use. Condenser microphones are ideal for studio recordings, dynamic microphones are suitable for live performances, while ribbon microphones offer rich and natural sound. However, an excellent microphone alone is often not enough to achieve a great sound result. The final outcome is influenced by many factors: the intellectual, emotional, and conceptual content of the music, the skill and preparation of the composer, performer, and sound engineer, the quality of the musical instruments, the acoustics of the space, microphone placement, recording and playback equipment, as well as the listener's ability to appreciate the music.

Therefore, it is essential to understand the characteristics and application of each microphone and consider all these factors to achieve the best possible sound quality.

The Athens Pro Audio team is always at your disposal to guide and inform you on all technical and non-technical matters, helping you choose the right microphone for your specific needs.