Microphones

Microphones: The technical Basics Microphones are used whenever the sound of a voice or an instrument needs to be reinforced – either on stage, in a rehearsal room, at presentations or recording at home or in a studio. There are three main technical characteristics that distinguish microphones from each other. These characteristics are important to understand to make the best choice for your needs:

Transducer type: How does the microphone physically pick up the sound and convert it into an electrical signal? Polar Pattern: From which direction does a microphone pick up the sound? Frequency Response: Is the output level or sensitivity of all frequencies the same?

Introduction

Types of Microphones 1. Dynamic Microphones:- A physical cone acts like a lens to concentrate the

incoming sound waves. Dynamic microphones employ a diaphragm, a voice coil and a magnet. The voice coil is surrounded by a magnetic field and is attached to the rear of the diaphragm. The motion of the voice coil in this magnetic field generates the electrical signal corresponding to the picked up sound.

2. Ribbon Microphones:-A ribbon microphone is a type of dynamic microphone that uses a thin electrically conducting ribbon placed between the poles of a magnet. Ribbon microphones are typically bidirectional. They pick up sounds from in front of the microphone and from the rear but not the side (90 degree angle).

3. Condenser Microphones: Condenser microphones are based on an electrically-charged diaphragm/ backplate assembly which forms a soundsensitive capacitor. All condenser microphones need to be powered: either by batteries in the microphone or by phantom power provided by a mixer. Condensers are more sensitive and can provide a smoother, more natural sound, particularly at higher frequencies.

Characteristics

• Robust and Durable

• They can be relatively inexpensive

• They are not sensitive to changes in humidity

• They don’t need internal or external power to operate

• They usually have a resonant peak in the mid frequency response

• Can be weak in the high-frequency response above 10 kHz

There are some common applications where you'll typically find dynamic microphones:

• Sound Reinforcement

• Snare Drum Miking

• Guitar Miking

• Voiceovers And Broadcasts

Dynamic Microphones

Characteristics

• They have a relatively flat frequency response

• They have a better high frequency compared to Dynamic Microphones

• They don’t need internal or external power to operate

• They are somewhat fragile and require care while operating

• They are moderately inexpensive

Ribbon microphone applications include:

• Miking Cymbals

• Miking the bass

• Miking the piano

• Electric Guitars and Acoustic Guitars

• Brass Instruments.

Ribbon Microphones

Characteristics

• They have extended high and low frequency response

• Good once are sometimes expensive

• They require either internal or external power

• Large diaphragm models can be relatively bulky

• Low cost models can suffer from poor or inconsistent frequency response

• Humidity and temperature effect performance

Condenser microphone applications include

• Miking Cymbals

• Drum Overheads

• Piano

• Acoustic Guitar

• Vocals

• String Sections.

Condenser Microphones

Microphones: Polar pattern / Directionality

The polar pattern of a microphone is the sensitivity to sound relative to the direction or angle from which the sound arrives, or easier worded how well the microphone “hears“ sound from different directions.

The most common types of directionality are: Omnidirectional, Cardioid and Super cardioid

Polar Pattern/Directionality

• A cardioid microphone has the most sensitivity at the front and is least sensitive at the back.

• It isolates from unwanted ambient sound and is much more resistant to feedback than omnidirectional microphones. That makes a cardioid microphone particularly suitable for loud stages.

Cardiod

• Supercardioid microphones offer a narrower pickup than cardioids and a greater rejection of ambient sound. But they also have some pickup directly at the rear. Hence it is important to place monitor speakers correctly.

• Supercardioids are most suitable when single sound sources need to be picked up in loud environments. They are the most resistant to feedback.

Supercardioid

• The omnidirectional microphone has equal output or sensitivity at all angles, this means it picks up sound from all directions. Therefore the microphone has not to be aimed in a certain direction which is helpful especially with lavalier microphones. A disadvantage is that an omni cannot be aimed away from undesired sources such as PA speakers which may cause feedback.

Omnidirectional

• A microphone with a figure of eight polar pattern picks up the sound from in front of the microphone and from the rear but not the side (90 degree angle).

• Microphones with this Figure of Eight polar pattern are typically ribbon or Large Diaphragm Microphones.

Figure of 8

Flat frequency response

All audible frequencies (20 Hz – 20 kHz) have the same output level. This is most suitable for applications where the sound source has to be reproduced without changing or “coloring” the original sound, e.g. for recording.

Tailored frequency response

A tailored response is usually designed to enhance a sound source in a particular application. For instance, a microphone may have a peak in the 2 – 8 kHz range to increase intelligibility for live vocals.

Frequency Response Curves

The frequency response is the output level or sensitivity of a microphone over its operating range from lowest to highest frequencies. Generally two types exist

This construction of the Dynamic Microphone gives the dynamic mic its robustness, but because the diaphragm is relatively heavy, that means that it can't respond to sound waves quickly, which means its high frequency response beyond 10 kHz is usually limited.

Frequency Response of Dynamic Microphones

(The above is a Frequency Response Curve is of a Shure SM 57 Instrument Dynamic Microphone)

Ribbon mics also have a smoother response than dynamics, since they don't have a midrange presence peak like a dynamic microphone usually does.

Frequency Response of Ribbon Microphones

(The above is a Frequency Response Curve is of a Shure KSM353/EDPremier Bi-directional Ribbon Microphone)

1) Small Diaphragm Condenser Microphones

The small diaphragm versions also have a slightly lower frequency response

Frequency Response of Condenser Microphones

(The above is a Frequency Response Curve is of a Shure KSM141 Condenser Instrument Microphone)

2 ) Large Diaphragm Condenser Microphones

A large diaphragm versions have a presence peak in the 8 to 12 kHz range, which makes them a favorite for vocalists

Frequency Response of Condenser Microphones

(The above is a Frequency Response Curve is of a Shure KSM42Large Dual-Diaphragm Vocal Microphone)