Thursday, 23 May 2013

Microphone Madness Part 1

Last week we discussed the importance of cables in a sound system and that they are in fact the most important component of the system.

Second on the list of importance is the microphones you use.

There are two types of microphone commonly used in modern sound systems. Dynamic Microphones and Condensor microphones (There are other types as well but we won't go into them here). Within these two categories microphones have a property that we call "pattern".

Dynamic Microphones are basically a small speaker, a diaphragm inside the mic vibrates with the sound in the air generating a small electrical voltage. Its the exact opposite of the way a speaker works and in actual fact you can hook up a speaker to a mixing desk input and use it as a dynamic microphone (albeit a fairly low quality one).
Dynamic microphones are used for vocals and on many instruments. What makes them particularly useful is the way they respond to bass. The closer the signal source to the microphone the more bass will be in the signal. This is called "Proximity Effect" and is most useful on vocal microphones. You may often see artists pull away from the mic during a high note to emphasise the note and then come in close when singing low to emphasise the low frequencies (think Barry White). The most famous dynamic microphone is the Shure SM58 and SM57 (basically they are both the same mic) which were the staple microphone for vocals and guitars for 30+ years. Today there are a wide range of dynamic mic's available. Dynamic microphones are generally not great at picking up very high frequencies, due to the fact that the large heavy diaphragm needs to be moved by the sound source and high frequencies are low in energy.

Condenser microphones work very differently to Dynamic Mics. A Condenser mic has two tiny plates inside it with a voltage between them. When the top plate is vibrated by the sound source, the capacitance between the two plates changes causing a signal to be generated. Condenser mics therefore need a power source to work and this is the most obvious external difference that you can use to identify a Condenser mic. The power source either comes in the form of an internal battery or power is delivered from the mixing desk down the microphone cable in the form of "Phantom Power".

Because the top plate on a Condenser mic is much smaller and lighter than a diaphragm of a dynamic mic, the Condenser mic is very good at picking up high frequencies. Condenser mics are also far less sensitive to the Proximity Effect so pick up bass signals evenly no matter how close or far away from the sound source the mic is. This is why you most often find Condenser microphones in recording studios, however they also have many applications on live stages.

Below is a summary of where you should use each type of microphone in a live situation.

Dynamic
  • Kick Drum
  • Snare
  • Tom Drums
  • Bass Guitar
  • Guitar
  • Vocals
  • Brass
Condenser
  • Hi Hats
  • Drum Overheads (Cymbals)
  • Choirs
  • Vocals (think Opera)
  • Brass
  • Kick Drum (when you want more high frequencies)