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Although not quite as widely used these days, the ribbon microphone is capable of providing very high quality sound.
Ribbon microphones are available from many manufacturers including many of the top names.
Ribbon microphone construction
The ribbon microphone consists of a corrugated aluminium ribbon suspended edgewise between the poles of a magnet.
The ribbon microphone is designed so that there are only very small gaps between the edges of the ribbon and the magnet sides. This means that the ribbon is moved by the velocity of the air rather then the sound pressure acting upon it.
As a result of this feature the ribbon microphone is known as a velocity microphone.
As the ribbon microphone has a single conductor passing through the magnetic field (unlike the dynamic moving coil microphone where several turns of the coil move through the magnetic field), the ribbon microphone has a low output impedance. To overcome this these microphones normally have an internal step up output transformer. Modern ribbon microphones use high performance magnets and efficient transformers and their output can sometimes exceed that of a dynamic microphone.
Ribbon microphone features
There are several aspects to the ribbon microphone – it offers a variety of features.
- Fidelity: The electrical version of the sound quality is very high when using a ribbon microphone. The mass of the ribbon is very low in view of the fact that it is particularly thin. This means that it has a low inertia and it has a good high frequency response.
- Resonance: The resonance frequency of the microphone is high – well above the audible region and therefore it does not colour the response. This results in a good flat response, and it sounds less bright than a moving coil microphone and as a result it produces a more pleasing sound.
- Directional pattern: The most common directional pattern for ribbon microphones is a bidirectional figure of eight pattern. In addition to the standard bidirectional pick-up pattern, ribbon microphones can also be configured to have cardioid, hypercardioid, omnidirectional, and variable polar patterns, although these configurations are much less common.
- Use with public address systems: The flat response means that public address systems can be used with a higher gain that with other types of microphone like the dynamic one that has a lift around 2.5 to 5 kHz. A lift of this nature advances the onset of acoustic feedback in this range, thereby reducing the overall gain that can be used. That said, some microphones deliberately have a peak introduced to give them a higher ‘presence.’ Check the frequency response before buying and using.
- Positioning: A ribbon microphone should not be placed too close to the speaker. If this is doen then the plosive sounds including ‘p’, ‘b’ and others produce a particularly bad pop. Also the bass is unnaturally enhanced.
- Sensitivity: The ribbon microphone does not have multiple wires cutting the magnetic lines of force – it is only the single ribbon and not the multiple turns of wire as in a moving coil or dynamic microphone. This means that the sensitivity is much less than that of a dynamic microphone.
- Robustness and durability: early ribbon microphones could be damaged by shock and even blowing into the microphone. Modern ribbon microphones are much more robust and can be used for a variety of applications including loud rock music.
Ribbon microphones do not require phantom power. As a result, care should be taken when using them with many mixers and other items of equipment that may supply phantom power. Older microphones can be damaged by the application of this voltage, although more modern microphones are much more resilient.
The ribbon microphone is an electrically simple design with no active components. It used to be considered as the microphone of choice for high quality audio applications. Even though other types of microphone have drastically improved their performance, new ribbon microphones have raised the bar even further offering improved performance, reliability and robustness.