Now, if a tree falls down in the woods and no one is around to hear it, does it make a sound? Yep, that old gem, and while I’m not too sure just what kind of ancient philosophical secrets that overused riddle was trying to tell me, what I did get out of it was that unless you have the right tools for the job, it makes no difference. If there are no ears to listen to that tree fall, then whether it happened or not doesn’t really matter if you’re there, right? And now, let’s say you’re trying to create that perfect track – if you don’t have the right mic for the moment – the one that lets you truly listen to what you’re trying to record – then it’s pretty much a waste, wouldn’t you say? And while the use of microphones is so widespread to the point where most people carry them in their pockets (via cell phones mainly), there are still a good number of people out there who have no idea about the amount of variations among them, let alone how these suckers work. So, whether you will be using microphones for recording music tracks or as part of a film or movie, everyone can benefit from understanding a few of the basics when it comes to mics. From their different variations to some of the more commonly used terms, we here at PAL would like to show you some of the ins and outs of the microphone in order to help you get the most out of your equipment because once you truly are a master of your gear, you will be able to hear a lot more than just some old trees falling.
Before we get started, check out our Microphone 101 Glossary for a quick brush up many of the terms we will be using along with other general microphone jargon that should make you at least sound like you know what you’re talking about!
How Microphones Work
Harkening back to my knowledge of basic natural physics, sound is simply small variations in air pressure at a specific location such as a dog, car, person, airplane – or whatever else makes a sound. But for that sound to be actually heard, we need a listener to complete the cycle otherwise no one hears it, much like that tree in the woods. Obviously, that’s what our ears do, but when it comes to audio, we have the microphone. For those of you out there that don’t mind me getting a little technical, a microphones are in the category of equipment know as transducers. Transducers are devices that convert one form of energy to another and with the case of microphones, they convert acoustic energy into electrical energy which can be heard by the mixer, speakers, computer software and all that other great stuff we use mics with.
We all have probably heard of a few of the different variations of microphones out there, such as passive and active, or maybe a condenser, but it should be said that there is more than one way to describe or categorize a microphone, such as either by its mechanical or electrical properties. The most basic way of describing a microphone is by the method it uses to convert acoustic energy, and the most common in this category is the dynamic mic. These are those rugged familiar types that you see everywhere from live concerts to podiums during speeches. Dynamic microphones are equipped with a small diaphragm (usually about the size of a quarter or a nickel) which is made of thin, lightweight material. At the center of the diaphragm is a small coil of copper wire which – along with the diaphragm – sits suspended on top of a circular magnet. As sound travels through the diaphragm, it moves up and down which pulls the coils through the magnetic field, which in turn creates electricity. Although not much, enough of an electrical signal is created for use in recording or through a PA system. Compared to other kinds of mics out there, these guys are relatively inexpensive, resistant to moisture and have the potential to handle a good amount of high gain which helps with negating feedback, making them perfect for loud environments. But like anything else, they’re not perfect, and one of the most common problems is that these mics don’t handle different frequencies of the audio spectrum the same, meaning you will need to get the right dynamic mic for the right job, such as the AKG D 112 for example (pictured above) which is designed to focus on bass, or simply use multiple types of mics as is the norm in audio engineering.
The next most popular variety of microphone is the condenser mic. A condenser is pretty much what we call a capacitor today by the way, in case you’ve heard both terms used for this mic. Although there are plenty of variations within condenser mics, they all typically work by using a back plate and a small diaphragm which each act like an electrical conductor. When sound vibrates between the diaphragm and the back plate, it changes the capacitance (the amount of electrical charge being held) of the circuit. This change in capacitance is then given off as a small electrical signal that is then amplified by a power source in order to then be used for things such as recording. Unlike dynamic mics which get their electrical charge from the magnetic field caused by the vibrating copper coil placed above its magnet, condenser mics need an external power source in order for them to function, which in the case of a studio condenser mic comes in the form of phantom power.
Compared to dynamic mics, condensers typically record in much better quality and are far more sensitive to sound due to the smaller amount of room needed to distinguish changes in frequency. This added sensitivity and high fidelity is what makes condenser mics the choice for high quality studio recordings but again, they are not perfect and the same thing that makes them great for in studio recordings makes them nearly unusable for live shows; while condensers work great for recording vocals or an acoustic guitar in a controlled studio environment, they are typically avoided for use in live performances since their added sensitivity makes them highly susceptible to high gain feedback from all of the background noise they pick up, unlike dynamic mics which only pickup what is generally near them.
Ribbon microphones get their name from the ribbon shaped piece of metal used to generate the mic's magnetic field. The ribbon itself is connected to the microphone’s signal output. Like dynamic microphones (which is what this mic falls under), ribbon mics generate electrical signal through magnetic induction, which is pretty much what happens when acoustic energy makes the ribbon vibrate on top of the mic’s magnet, creating a magnetic field that then produces electricity in the form of an output voltage signal that we record as sound. One of the more interesting aspects of the ribbon mic is that it detects sound in a bi-directional pattern thanks to the ribbon shape of its transducer, meaning that it can records sound both in front and behind equally. While this bi-directional recording can be a pain when trying to do a regular stereo track, more creative uses for the ribbon mic make them perfect for certain applications, such as creating the sense of spatial surround sound when played through headphones or speakers via a ribbon mic recording technique known as a “Blumlein Pair.” Ribbon mics can also be made to be uni-directional by closing off one side of the mic through an acoustic trap or baffle. Back when ribbon mics first came into the scene, they were prized for their outstanding low frequency recording capabilities, but this could only be attained if the ribbon was very loosely suspended, making these high quality mics very fragile. Luckily for us, with the use of newly implemented nano-materials, ribbon mics are just as great on that low-end without that fragile build.
Alright, so that’s it for part one of our Microphone 101 lesson but make sure you come back tomorrow and later this week as we will continue to further explore the more technical aspects of the microphone. Tomorrow, we will be taking a closer look at some of the aspects that differentiate one mic from another along, some common microphone accessories along with a few helpful maintenance tips that should get you the most life out your equipment. Until next time.