What Microphone Should I Use?
Updated: May 28
I hear this question often. Everyone wants to know what microphone to use and today we are going to fill you in. This is Spencer Miles from Spencer Studios, a recoding studio in Lancaster, Pa. The answer to your question is that it depends on the goal for your music and how you plan to use the microphone.
There are four main factors that change how a microphone sounds. These variables are transducer type, polar pattern, distance, and axis. This article is going to use graphs from a spectrum analyzer to show how each factor impacts frequencies when recorded.
Transducer type refers to the construction of the microphone. Are we using a large diaphragm condenser, small diaphragm condenser, ribbon, or dynamic microphone. Polar pattern refers to where the microphone is listening. Do we have a cardioid / uni-directional (front only), bi-directional (front and rear), or omni-directional (all directions) microphone? Distance is generally broken into close, mid, and room or far microphone placement technique. Axis coloration involves rotating of the microphone from on axis pointing directly at the source, all the way to 90degrees or off axis from the sound source.
Let's start off with distance. The first thing you should know about mic placement is that placing the microphone close to the sound source can cause what we in the audio industry call proximity effect or bass build up. Certain polar patterns are more susceptible to this than others. Lets look at a large diaphragm microphone with multiple polar pattern options. These measurements were taken at a distance of three inches.
On the left we have the microphone set to cardioid and the right we have it set to omni. You can notice at around 100hz a sizable build up of around 6db however, on the right we have a much smoother bass response. The cardioid pattern is most suspectable to bass build up followed by bi-directional, with omni being the least impacted by this occurrence.
While we're on the topic of polar responses let's look at the the same large diaphragm condenser placed 3 feet away.
From left to right we have cardioid, bi-directional, and omni directional polar patterns. The high frequency response remains the same however, as we move between the graphs the amount of bass boost is reduced both in level and in band-width. As we move farther away as a whole, proximity effect is less of an occurrence.
The next variable we will look at is distance. We will continue to measure our large diaphragm condenser using the cardioid pattern. The distances chosen were 8in, 3ft, and 8ft.
Notice primarily the changes in the bass and midrange response as the microphone is moved farther away. Also note that when we increase the placement distance we also start to capture increasing amounts of reflected sound altered by the room frequency response and decay rate in addition to the direct sound from the sound source.
On the same topic lets add in the different transducer types. From top to bottom we have large diaphragm condenser, small diaphragm condenser, ribbon, and dynamic microphone responses. The distances shown are the same as above, 8in, 3ft, and 8ft.
While it is important to note that frequency responses can vary greatly even among microphones of the same transducer types these graphs can be viewed as characteristic to each category. Large diaphragms commonly referred to as being warm often have a little bump in the bass region. Small diaphragms commonly have a brightness to them caused by peaks in the high frequency region. Ribbons are known for their smooth response and ability to round off a harsh sound. This characteristic is evident in the rolling off of high frequencies. Dynamic microphones often have a very clear and sibilant sound which is accomplished by rolling off much of the low frequency "mud."
We have almost covered the main factors with just axis coloration left to explore. When we rotate a microphone, changes in the polar pattern's off axis response can have an impact on what is recorded. This last test was conducted using a large diaphragm at 3 feet set to the cardioid pattern. As a whole this rotation diminishes high frequency content. The angles used were 0, 15, and 45 degrees. Axis response probably makes the least amount of difference out of each factor however, is still beneficial. Watch how from left to right the distance in db of the bass and mid regions becomes closer to the peak of the high frequencies. The response becomes slightly smoother as the high frequency content is reduced.
At this point you may begin to wonder if some of these variables actually matter. On their own they may be small but when each is combined you can have wildly different results depending on choices of the audio engineer. A cardioid large diaphragm placed at 8inches on at 15 degrees could have a massive amount of proximity effect. A ribbon microphone placed at 8 feet away rotated to 45 degrees off axis could be very dull sounding. The answer to the question of what microphone should I use really depends on the source you are recording, your goals for that sound and are dependent on your selection of transducer type, polar pattern, placement distance and axis rotation. There is no magical microphone. Audio production is a creative art influenced by scientific choices. Prior to recording you must know what your goals are and use these variables to help you reach your goals. If I wanted a smooth trumpet the later option above might work well. If I wanted a monster bass guitar the first option placed on the cabinet might suffice.
If you want to know more consider scheduling a free session with us,
Spencer Miles Spencer Studios 313 W Liberty St, Lancaster, PA 17603