Confused about Condenser Microphones and how to use them? We answer all you questions in this article so check it out!
Have you ever heard the term condenser microphone before and wondered what it was all about? Perhaps like me at first you thought it was something to do with a refrigeration unit (lol). Well today we are going to take a look into what a condenser microphone is and remove any doubt in your mind. We will look at the different parts in a condenser microphone and what their purpose is, how these parts work together to create a signal, strengths and weaknesses of condenser microphones. And finally we will cover off some of the key details you might want to look out for when researching/purchasing a condenser microphone.
The short and sweat version of this article is… a condenser microphone uses a capacitor to transduce, sound energy into an electric current or signal. This signal is then amplified and sent out through speakers or can be sent to a recording device and possibly further translated into digital information for use in a DAW.
So if that was not enough for you, lets take a closer look by starting with a tear-down of the components.
A condenser microphone is characterized by the use of a capacitor as a transducer, changing sound waves or sound energy into a current (electric energy). The label `condenser` should actually be `capacitor`, but over time the name condenser has stuck.
Using the diagram above as our guide, we see the capacitor inside the mic is setup so that there is one very thin membrane acting like a diaphragm. This might be made from a non conductive material and then lightly sprayed with gold to allow it to hold a charge. There is another conductive plate similar in shape but significantly thicker which is held very close to this membrane, just like the two conductive surfaces in a capacitor. If this thin diaphragm is hit by sound waves then the distance between the two surfaces changes, resulting in a change in capacitance. This change in capacitance is the `sound signal` sent out of the microphone and to a device for recording or further amplification.
Capacitors are also used in cameras to power the flash, this is because capacitors are very quick at releasing the charge they hold. This is an important aspect to remember as this effects the uses a condenser mic is good for which we will discuss later in this article.
As you can imaging (or maybe not) this change in capacitance signal is very small with a very high impedance and not yet ready to travel out to a speaker or recorder. So it first must be amplified, and there are two ways condenser microphones do this.
- Field-effect transistors (FET) Amplifier
- Tube Amplifier
The FET amplifier is great in this case since it is able to take a signal with very high impedance and output a very low impedance. Low impedance is desirable and we will discuss impedance later in this article.
While the most important part of the mic with regards to sound quality is the capacitor there can be slight differences in the signal depending on if a FET ro Tube amp is used. The main differences are that a tube amplifier might have warmer sound due to the way it amplifies a signal and a FET amp might have a crisper sound, better catching the soft nuanced sounds.
Finally a condenser microphone requires a charge since to have capacitance the to plates need to be charged. There are two main ways a condenser microphone can get a charge to the capacitor:
Phantom Power: usually a supply of 48v to the microphone which is sometimes increased inside the mic if necessary. Most sound cards and mixers will have dedicated phantom power mic inputs.
Electret: a special type of capacitor that has a built in charge often produced by a magnet
Here we discuss some of the uses condenser microphones are well placed for and some situations where they are not.
To open up the discussion I would like to take you back to the thin diaphragm discussed earlier. These diaphragms can be so thin that it makes them incredibly sensitive and so what this means is that a condenser microphone can sound louder than other types of microphones. On the flip side of that a condenser microphone is better able to pick up very delicate and slight sounds. This sensitivity also lends it self well to a flat response curve assuming care is taken in the manufacturing process. When you combine this with the idea discussed earlier about a capacity being very quick to discharge, what you get is a very detailed and accurate recording.
In the studio – Good
This sensitivity means that it is a great choice for use in a recording studio on vocals or acoustic instrument. A condenser microphone will better at picking up the soft nuanced sounds from a vocalist e.g. the husky breath sounds or slight movements of the mouth. It is also great for recording a guitarist, for example when you want to hear not only the notes but the sound of a pick as the player strums and movements across the fret-board as the player changes cords.
Further to live instruments condenser microphones are great when recording high frequency and high speed sounds like cymbals from a drum kit. They can do well when hung above a drummer to catch the hi-hat sounds or the tap from a stick on a side drum.
Live performance – Not so Good
This sensitivity to sound we have discussed also has its drawbacks and the main one being that condenser microphones have the tendency to distort in high volume situations. This makes them not an ideal mic when you want to amplify a rock band on stage, take a recording of a drum-kit up close or from a guitar/bass amplifier. In these cases dynamic microphones are preferred.
Jargon you should know
Here are a few terms that you should have an understanding of should you find yourself in the market for a condenser microphone. These will help you better understand the differences between the many different options available. If I could recommend just one for you to remember, it would be `Response Curve` which should not be confused with `Frequency Response`. So if time allows please have a look at the below but if not skip down to Response Curve.
Impedance is basically how much a electric circuit will resist a change in current, this is relevant to us in this discussion because the signal being created by our mic is essentially a change in current. So it would make sense then, that we want the impedance to be as low as possible right? Yes!
So when looking for a microphone check out the impedance rating. In general, anything below 600 ohms is considered to have low impedance. Condenser mics are known for having low impedance ratings.
Low impedance is also good for when you need to place a mic far away from the recording device or amplifier. This is because audio quality degrades as impedance rises, and as you increase the length of the cable, resistance rises, and as resistance rises, impedance rises etc.
Warning: be sure that what ever you are plugging into whether it be a mixer or sound card etc, that is has a higher impedance than the mic and cable going into to. If the source (mic and cable) has a higher impedance and the target, then this could result in degraded audio.
What direction or directions, can the microphone receive and interpret sound enery. This information can often be found in the accompanying documentation with the mic or on manufacturers web page. You can see this information in the spec sheet for the Shure SM81 condenser mic (referred to as the `Polar Pattern`) here or below.
You can see at what angles around the mic you will be able to pick up different frequencies. Looking at the diagrams it is easy to tell that this particular mic is quite directional meaning that it is predominantly `listening` to sounds directly in front of it, picking up only a little information from the sides and almost nothing directly behind the mic.
This is the most common direction among mics, but there are also omni directional which means that a mic can `listen` to sounds from any direction evenly. There are even mics that can pickup sounds from in front and behind while muting out the sound coming from the sides. Shotgun mics are popular due to their ability to be very focused which is great for Video work where you only want to hear the person on screen talking.
So if Direction (discussed above) is what direction(s) the mic is in, the response curve is what frequencies the mic listens to. What you really want here is as flatter response curve as possible. Take the SM81’s response curve below:
From the chart the SM81 is able to pick up sound around 0 db all the way to approximately 17 kHz then it starts to drop off. The same can be said when you look at the curve around the 5k Hz mark and then even more drop off at the 3k Hz mark.
In case you are confused by the arrows left of the 3 kHz mark, they indicate the frequency response curve that will be applied depending on what position the filter switch is in on the mic. This allows you to completely remove some of the low end from the recording outright.
The Maximum Sound Pressure Level (SPL) is basically the loudest sound the microphone can record before it will start to audible distort. In the old days condenser microphones were quite limited when it came to SPL, barely reaching 120 db. But today’s condenser mics have greatly improved on this. With our SM81 you might see some distortion around 131 db, which is not to worry as you are very unlikely to come up against this volume considering a drum kit is around 125 db and the loudest human scream is around 128 db.
Here are two of my favorite options because they are built to last and actually have really great sound quality. They will be sure to last you a long time.
Shure SM81 – my favorite
Audio-Technica AT2010 – best price
So hopefully this article was helpful in giving you an understanding of what a condenser microphone is and how it works. I also hope that there is enough information in this article to help you should you decide to purchase a condenser microphone in the future. If anything was not clear or you have further questions about condenser microphones then let me know if the comments below and I will be happy to help out where I can!
Do you have any experience with condenser microphones? Perhaps you have a favorite mic or one that you would avoid? Feel free to share your thoughts in the comments section below with us!
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Thanks for reading!