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Microphones


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A microphone is an example of a transducer: a device that changes information from one form into another.

 

Sound information exists as patterns of air pressure, and the microphone changes this information into patterns of electric current. A variety of mechanical techniques can be used in building microphones, the most commonly encountered in DJ Microphones is the dynamic design.

 

 

 

 

DYNAMIC MICS

 

In the dynamic microphone, sound waves cause movement of a thin metallic diaphragm and an attached coil of wire. A magnet produces a magnetic field that surrounds the coil, and motion of the coil within this field causes current to flow. It is important to remember that current is produced by the motion of the diaphragm, and that the amount of current is determined by the speed of that motion. This is known as Velocity Sensitive.

 

 

Any microphone will produce distortion when it is overdriven by loud sounds. This is caused by various things. With a dynamic mic, the coil may be pulled out of the magnetic field. Sustained overdriving or extremely loud sounds can permanently distort the diaphragm, degrading performance at ordinary sound levels. Loud sounds are encountered more often than you might think, especially if you place the mic very close to you mouth (ever heard a Drum 'n' Bass MC?)

 

 

 

 

CONDENSER MICS

 

Condenser mics operate on an Electrostatic principle. It is essentially a capacitor, with one plate of the capacitor moving in response to sound waves. The movement changes the capacitance of the capacitor, and these changes are amplified to create a measurable signal. Condenser microphones usually need a small battery to provide a voltage across the capacitor, or require Phantom Power (+48v) from the Mixing Desk.

 

 

 

 

 

PICK UP PATTERNS / DIRECTIONAL RESPONSE

 

OMNI -

 

 

The simplest mic design will pick up all sound, regardless of its point of origin, and is known as an Omni-Directional microphone. However, as these mics pick up sounds from all directions, they are also liable to pick up the sound coming from the loudspeakers and cause feedback, so they are generally not suited for live or DJ use.

 

 

 

 

BI-DIRECTIONAL -

 

 

This design accepts sound striking the front or rear of the diaphragm, but does not respond to sound from the sides. The fact that the mic accepts sound from both ends makes it difficult to use in live situations.

 

 

 

 

CARDIOID -

 

 

This pattern is the most popular for live DJ or MC use. The concept is that the mic will pick up the sounds it is pointed at, but the reality is different. The first problem is that sounds from the back are not completely rejected, but merely reduced by about 10-30 dB. This can surprise careless users.

 

The second problem, which is a severe one, is that the actual shape of the pick-up pattern varies with frequency. For low frequencies this is an Omni-Directional microphone. For this reason it is advised that you never add bass frequencies when setting your mic EQ.

 

A third effect, which may be a problem or even a desired feature, is that the microphone will emphasise the low-frequency components of any source that is very close to the diaphragm. This is know as the Proximity Effect, and many DJ and Radio announcers rely on it to add bass to a basically light sounding voice.

 

 

 

 

MICROPHONE CHARATERISTICS

 

FREQUENCY RESPONSE -

 

This refers to how a mic responds to frequencies in the human range of hearing (20Hz - 20KHz). Some react equally all through the frequency range, with a flat frequency response. Others can be made to emphasise or de-emphasise some parts of the audio spectrum, having a particular Sonic Character.

 

Low frequency response, around 3-25Hz, can be easily introduced in the audio chain though many sources including - traffic rumbles, machinery, etc... all working in the sub-audio range. To avoid this:

 

Isolate the mic from vibration

Use a mic with a restricted low frequency response.

Use a 'Roll Off' filter or EQ.

 

 

 

TRANSIENT REPONSE

 

This means how quickly a mic's diaphragm reacts, the faster the reaction, the better the response. Dynamic mics have a tendency to react quite slowly, whereas Condenser mics react very quickly.

 

 

 

SENSITIVITY RATING

 

Output level in Volts given a specific and standard input signal in dBSPL (Sound Pressure Level).

 

 

 

OUTPUT IMPEDANCE

 

The most common are 50Ω, 150Ω to 250Ω (ohms)

 

 

 

 

HOLDING THE MICROPHONE

 

Of course, there is a right way and a wrong way to hold a mic.

 

You should always hold the mic by the stem with your hand away from the pick-up area. Cupping your hand over the top of the mic may look 'cool', but it will have a dramatic affect on the performance, causing the sound to be muffled or distorted. It can also affect the Polar Characteristics and cause feedback.

 

This person does not know how to hold a microphone.

Look, even the guy next to him is like...."yo check my man hold the MIC like a pro braapp!"

 

idiots

 

 

 

This guy, is obviously a master..

 

 

 

The angle at which you hold it is crucial. A cardioid mic is designed to pick up the sound directly from the front and should be held with the top directed at your mouth, and as close as possible to your lips. Holding the mic at an angle or too far away will reduce the output level requiring more amplification and could lead to distortion if it continues.

 

Microphones such as the popular Shure SM58 have a ball shaped head: this serves 2 purposes. Inside the ball is a thin layer of acoustic foam; its job is to prevent overload of the mic capsule caused by gusts of air from your mouth when certain words or letters are spoken. Try holding you hand in front of your mouth and say a word beggining with 'P'. The air will hit your hand. This excessive flow of air will cause the sensitive mic capsule to overload, causing a popping sound through the system.

 

 

 

 

USING THE MICROPHONE

 

If you are going to use a mic you must develop a technique that makes you heard above the music. Simply adding more volume may cause undesirable feedback or 'howling'. Try not to sound 'mic shy'. Project your voice as though the mic was not there and you were trying to be heard!

 

This will help you sound confident and professional, but be careful not to shout! It is a case of speaking up, not screaming at the audience. Adding a little high-mid EQ will sometimes help with clarity, but again avoid feedback.

 

 

 

 

CONNECTIONS

 

Typically most microphones use the XLR connection. This is a professional audio connection and gives great audio signal.

 

 

 

 

 

CONCLUSION

 

Ok so thats pretty much the basics of microphones. So briefly what have you learned?

 

If you want a microphone for live gigs its best to use a Dynamic mic.

If you want a microphone for studio use, its best to use a Condenser mic (remember Phantom Power!)

 

When using the mic dont hold it like a twat, hold it properly and you'll hear the difference.

 

The different types of pick up responses are important, make sure you have the right response for the right use.

 

 

 

 

 

 

well i hope this helps, writing this has refreshed my memory on a few things!

 

 

peace - good luck

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so sometimes you got to cup the mic or it sounds horrible

 

 

erm no

 

lol

 

sorry but thats just wrong

cupping the mic is just fucking stupid, thats wat makes it sound horrible

 

and its made worse that people watching think thats how to properly hold a mic

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so sometimes you got to cup the mic or it sounds horrible

 

 

erm no

 

lol

 

sorry but thats just wrong

cupping the mic is just fucking stupid, thats wat makes it sound horrible

 

and its made worse that people watching think thats how to properly hold a mic

 

I sort of agree but cupping the mic drastically increases the proximity effect. Since this makes your voice typically sound deeper a lot of people assume that they sound 'better' when they do it, because they think that's how their voice should sound like rather than the weak nasally voice they've really got.

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  • 8 months later...

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