In the previous article I talked about the various types of recording equipment, from hand-held portable recorders to laptops with an audio interface of some sort. The hand-held recorders have built-in microphones, which is tremendously convenient for the user, but when we are using a laptop with an audio interface, a microphone is an integral part of recording acoustic instruments or voice. And so, we venture into microphones and their use.
Figure 1 - the portable vocal studio
There are many different microphones available, purpose-built for different jobs, and ranging from several hundred to many thousands of dollars. When you are looking to buy (doing your on-line research, of course), certain types become apparent, but they can be broken up into several groups. Every microphone is described by type and use - for example, a dynamic or condenser microphone with a particular type of polar pattern. A dynamic microphone is best described as durable and reliable - great for the rigours of live performance, or in a situation where very high volume levels are involved, such as recording a trumpet or a bass drum. They are often held by a singer, giving them something to do with their hands, or mounted on a stand for instrument mic’ing. The type of microphone you might see a rock band singer swinging around his head onstage, while the sound engineer freaks out completely at the back of the auditorium. The industry standard for this type of microphone has been the SM58 by Shure (since the 1960s)- by no means the only dynamic microphone available, but definitely a popular choice.
Figure 2 - the SM58 in hand
If you are in a more controlled environment with the intention of recording your performance, such as a studio or rehearsal room, your choice of microphone may be very different. Condenser microphones are more sensitive, with delicate components, and require power to run them. This power comes from the audio interface or mixer that the microphone is plugged into, and is supplied through a standard microphone cable (with 3-pin XLR plugs at both ends). If you look more closely at the audio interface when you plug the microphone in, you will see a small switch next to the socket labelled ’48V’ or ’phantom power’. When this is switched on, the unit will supply power to the condenser microphone through the cable. These microphones are usually held by a shock-mount, to prevent handling noise.
Figure 3 - Audio Technica condenser in its shock mount
I mentioned earlier that each microphone has a polar pattern, which is best described as the area around the diaphragm (the recording element of the microphone) that it will hear. Some microphones are designed to hear both in front and behind them, some in a 360 degree field around them, others just what’s in front of them, all by how their polar pattern is designed. The cardioid pattern allows the microphone to hear what is directly in front of it, and not hear anything behind it. In the case of the standard dynamic mic, the best way to record is straight into the top. With a condenser in a shock mount, the diaphragm is pointing towards the side of the microphone (called side address), so you should be pointing towards the brand logo on the side for ’best hearing’.
Figure 4 - the Shure microphone showing its cardioid polar pattern
For recording acoustic instruments, the pencil condenser microphone allows you to target the ’sweet spot’ of the instrument, if you want more emphasis on the body of a cello or the plucking of a guitar’s strings. For the purpose of recording in stereo (we have two ears, after all), these microphones are offered as matched pairs to give a realistic stereo feel to a recording.
Figure 5 - the pencil condenser
I've jumped around quite a bit in this short article, attempting to cover various aspects of microphone technology and technique, so if you encounter specific issues with your recording work, drop me a line via the Mentor page and I'll help where possible. There are numerous resources available via the Internet for microphone placement techniques, probably far too many, in fact.
For the string players among you, here’s an interesting article to give you some idea of what’s involved: http://www.soundonsound.com/sos/apr99/articles/recstrings.htm Images used are from manufacturer's websites