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I worked for BBC Television for 25 years as a sound man and I’d like to pass on some of the wrinkles and tips I’ve picked up during that time.
In our first video we talked about how moving coil microphones work. We’ll be looking at other types of mics in future videos, but this one is about connecting up.
All but the cheapest microphones have a 3-pin XLR male connector built into them. This mates with a female connector on a cable, like this, and the other end plugs into your mixer or camera or whatever.
Microphone cable is usually a pair of wires enclosed in a shield of metal braid.
Here are the conductors – this is the outer sheath, which surrounds these two wires that actually carry the signal.
The outer sheath is called the ground or earth connector and it’s connected to the metalwork of whatever the mic is plugged into – or it’s electrical earth if it happens to be made of plastic.
The outer braid is to screen the signal from interference from electrical or electromagnetic fields. The two inner conductors carry the tiny alternating signal current.
Actually, a moving coil microphone will work with a cable without an outer screen. But it will pick up noise and mains hum very easily, unless it is properly balanced.
However, capacitor or condenser microphones won’t work without the outer braid connected – but only because the power to operate the amplifier inside the microphone depends on having the earth or ground wire connected for it’s power supply.This is a condenser mike. I|’ll cut the earth wire.
More on this in a later video, when we talk about phantom power and condenser microphones.
The standard connections for the XLR connectors and cables are like this:
Pin one is the screen, or earth terminal: pin two is the “hot” or positive terminal; and pin three is the “cold” or negative terminal.
This “hot” or “cold” labelling of pins or terminals two and three is just a convention, but it’s important, because if everyone sticks to it, then the output from the diaphragms of the various microphones will move in the same sense whoever happens to be the manufacturer.
Why does this matter? It matters because if microphones are used close together – then although the diaphragms are moving together, if they’re connected the other way round there will be a cancellation of the sound, particularly at low frequencies.
This personal mike sounds fine. So does this one. Together they sound like this.
Now I’m going to change the sense, or phase, of one of them with this phase reversing barrel.
This is just an empty tube with the connections to pins two and three reversed. I’ll just plug it into the mixer:
Now listen: all the bass has gone, and as the mikes move around it sounds very strange. The connections to the diaphragms are now reversed, effectively meaning that the diaphragms are moving in opposite directions to each other, and we’re getting all sorts of cancellation of the sound waves. Imagine if this happened when you were recording music!
It’s exactly the same with your speakers by the way. If you accidentally connect them out of phase, the bass will disappear and it will all sound wrong, with no bass and no stereo imaging
I hope you found this interesting. Do let us know if you’ve got any suggestions or questions.
Thanks for watching!
thanks for looking in I worked for BBC television for 25 years as a sound man and I'd like to pass on some of the wrinkles and tips that I've picked up during that time in our first video we talked about how moving coil microphones work we'll be looking at other types in future videos but this video is all about connecting up all the cheapest mics have a 3-pin male XLR connector built into them and this mates with a female connector on the cable and the other end of the cable is plugged into your mixer camera or whatever microphone cable is usually a pair of wires enclosed in a sheath of metal braid here are the conductors this is the outer sheath which surrounds these two wires which actually carry the tiny signal the outer sheath is called the ground or earth connection and it's connected to the metalwork of whatever the mics plug into or in the case of a plastic equipment its electrical earth the outer braid is to screen the signal from interference from electrical or electromagnetic fields the two inner conductors carry the tiny alternating signal current and actually a moving coil microphone will work with the cable without an outer screen it'll pick up without this screen it'll pick up noise and mains hum very easily unless it's properly balanced I'm going to cut this earth while while I'm talking into this sm58 you'll see one two three four five six seven eight nine ten however capacitor or condenser mics won't work without the outer braid connected as I said capacitor or condenser mics like this one won't work without the outer braid connected because the power required to operate the preamp in the microphone depends on having the earth connected for its power supply this is a condenser mic it's plugged in now just like the other one I'm going to cut the earth wire more on this in a later video when we talk about phantom power and condenser microphones the standard connections for the XLR connectors and cables are like this pin one is the screen or earth terminal that's pin 1 pin 2 is the hot or positive terminal that's that one and pin 3 the middle one is the cold or negative terminal now this hot and cold labeling is just a convention but it is very important because it everybody sticks to it then the output from the diaphragms of all the various microphones that are manufactured will move in the same sense whoever happens to make them why does this matter it matters because if microphones are used close together then although the diaphragms are moving together if they connect to the other way around there'll be a cancellation of the sound particularly at low frequencies this personal mic sounds fine hello hello personal mic so does this this sounds absolutely fine and together they sound like this absolutely fine now I'm going to change the sense or the phase of one of them with this phase reversing barrel it's just an empty tube with the connections to pins 2 & 3 reversed I'll just plug it into the mixer I need the sex convert excuse the word sex now listen place is gone and as the mics move around it sounds very strange for connections to the diaphragm reversed effectively meaning at the diaphragms are moving in opposite directions to each other we're getting all sorts of cancellations of the sound imagine if this happened when you were trying to record music it's exactly the same with your speakers by the way you'll accidentally connect them out of phase the bass will disappear and it'll all sound wrong with no bass and no stereo imaging I hope you found this interesting do let us know if you've got any suggestions or questions thanks very much for watching bye for now you