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TPBLeap - Creative Futures

by JJ Vernon

Chapter 6 : Microphones

In Chapter 3 we discovered that a microphone is a transducer - that is something that converts one form of energy into another. In the microphone's case, sound goes into the microphone & what comes out of it is an analogue electrical signal.

Definition: ANALOGUE - something which is similar to or can be used instead of something else. Describes a recording which is made by changing the sound waves into electrical signals of the same type

Once the sound has been changed into a corresponding electrical signal by a microphone it can be sent on to other pieces of equipment. As sound engineers we will normally want to do one of two things with this signal.

  • Record it - so that it can be played back later
  • Amplify it - so that the sound is made louder through amplifiers & speakers

Microphones come in many, many shapes & sizes & there are numerous makes & models designed for particular purposes. As a sound engineer it is important for you to know a little about microphones so that you can select a suitable model for the task in hand.

DYNAMIC MICROPHONES - Are the most common type of mics. Their major advantage is that they are robust & will stand up to rough treatment, loud sounds & the occasional drop. When you see a rock star swinging a mic around by its lead, you can be fairly sure this will be a dynamic model! Dynamic mics have been the mic of choice for rock and roll concerts for decades with one particular model being by far the most common.

SM58

Dynamic mics can be comparatively cheap to buy & for live music are very often all you will need. If you would like to know how dynamic mics work you can click here:

http://www.mediacollege.com/audio/microphones/dynamic.html

For use in theatre, dynamic mics like this may not be appropriate. They need to have mic leads attached to them & are quite large.

Theatre audiences are not used to seeing actors using mics like this as they obscure the actors' faces & prevent the audience from believing in the story that is unfolding on stage. However if the show has a live band - like a musical or a pantomime -mics like this will come in handy for mic-ing up the instruments & the musician's amplifiers.

CONDENSER MICROPHONES - Are typically more fragile than dynamic mics & if dropped will most probably be broken. So again for this reason alone, they are probably not appropriate for theatre work. Condenser mics are generally more "sensitive" than dynamic mics. This means that for a given audio signal they will produce a larger analogous electrical signal. This means that condenser mics would be a better choice for recording quiet signals. Condenser mics are also able to capture high frequencies more accurately than dynamic mics. This will become evident when we look at different microphone model's frequency response charts.

Condenser mics will normally require power of some sort. This may be supplied by means of an internal battery (For theatre this is bad as it exposes you to the danger of a battery running out mid-performance.) More likely is that power is sent to the mic from the mixing desk down the mic cable. This is called "phantom power." Phantom power is normally 48 volts DC & the mic will draw the amount of power it requires.

On mixing desks you will normally see a button for each channel (or for several channels) normally marked as +48v. See picture below.

Phantompowerswitch

On this Yamaha mixing desk. You can see the switch marked "Phantom +48V. When this is depressed it will send power out of the desk to mics attached to the mic inputs numbered 1 through to 7/8.

If you would like to know how condenser mics work, please click on this link.

http://www.mediacollege.com/audio/microphones/condenser.html

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