Frequency response is one of the most common specifications when learning about microphones, as it is directly related to sound. However, what does a frequency response graph actually tell us about a microphone’s sonic characteristics, and what are the things that this graph cannot represent?
What Does Frequency Response Tell Us?
Frequency response is probably one of the most widely discussed specifications, because it is directly related to the most important aspect of using a Microphone: sound.
However, a specification such as 20 Hz - 20 kHz alone usually does not provide much useful information.
A frequency response graph provides more information because it shows the Microphone's tonal balance.
For example, if the graph shows that the high frequencies are boosted by around 6 dB, we can expect the microphone to produce a fairly bright sound.
However, a frequency response graph cannot tell us whether the listener will like the character or “texture” of that brightness. It also cannot tell us whether the sound will feel smooth or harsh to the listener's ear.
How to Read a Frequency Response Graph
To read a frequency response graph, the first thing to look at is the X-axis.
Frequencies are usually displayed on a logarithmic scale, because this representation is closer to human perception than a linear scale.
You can think of the logarithmic scale as being divided into octaves, where the frequency doubles. Therefore, the distance from 100 Hz to 200 Hz is equivalent to the distance from 1,000 Hz to 2,000 Hz, as well as from 10,000 Hz to 20,000 Hz on the graph.
To provide a general overview of the different frequency ranges, Neumann divides them as follows:
Below 40 Hz: Sub Bass
This is the sub bass range. Apart from the kick drum, the sub bass range contains relatively little musical information.
40 - 200 Hz: Bass
This is the bass range, which forms the foundation of sound.
The lowest note of a 4-string bass lies at around 40 Hz, while the lowest note of a guitar is around 80 Hz.
The lowest note of a male baritone voice is around 100 Hz, although notes this low are rarely heard. Most male and female pop vocals lie above 150 Hz.
200 - 500 Hz: Low Mids
This is the low mids range, where the body of most instruments is formed.
This is also the range where the human voice contains most of its energy.
500 - 3,000 Hz: Mid Range
The mid range plays an important role in sound character because this is the range in which the human ear is most sensitive to very small details.
Neumann provides an easy-to-understand example: telephones transmit very little sound below or above this range, yet we can still recognize the caller from just a single “hello”.
3,000 - 7,000 Hz: Presence
This is the presence range, which plays an important role in clarity and speech intelligibility.
Many consonants in speech fall within this frequency range.
7,000 - 14,000 Hz: Treble
The treble range plays an important role in our perception of sound brightness.
However, too much energy in this range can make the sound harsh and distracting.
This is also the range that contains sounds such as S and T in speech, as well as cymbal sounds and the sound of strings.
Above 14,000 Hz: Air Band
This is the air band, which plays an important role in recordings intended to create an “expensive” and “super-hi-fi” feel.
This range adds a sense of openness and “air” to vocals and string instruments, which is also why it is called the air band.
However, this range does not contain much musical information.
Comparing Frequency Response Graphs
When comparing frequency response graphs, it is important to pay attention to the scale of the Y-axis.
According to Neumann, some manufacturers use a very wide scale to make a highly variable frequency response graph appear flatter and smoother.
Neumann also notes that some less reputable manufacturers may produce frequency response graphs that are not based on actual measurements because they do not have the equipment required to perform the measurements.
An anechoic room together with specialized measurement equipment represents a significant investment, while drawing a graph with a pencil is much simpler and less costly.
Does a Frequency Response Graph Always Accurately Reflect a microphone?
Typically, microphones designed for studio use have a more balanced frequency response than Microphones designed for the stage. However, they are not completely linear either.
Most microphones tend to have a boost in the high frequencies, particularly in the presence and treble ranges.
Frequency response graphs can still be useful for comparison, such as identifying the position and degree of boosted frequency ranges.
However, Neumann notes that published graphs can sometimes be unreliable, particularly for lower-priced products.
Frequency Response and Sound Evaluation
A frequency response graph is a useful tool for understanding the Microphone's tonal balance and observing how different frequency ranges are represented.
However, a graph cannot describe the entire listening experience.
For example, a boost in the high frequencies may indicate that a microphone has a brighter sound, but looking at the graph alone cannot determine whether that brightness will feel smooth or harsh to the listener.
Therefore, reading a frequency response graph should be understood correctly: it is a way to read a microphone's frequency response characteristics, rather than the complete answer to the microphone's sound character.
Understanding frequency response is an important part of learning about and selecting microphones for a studio. However, alongside technical specifications, directly listening to and experiencing the equipment also provides another perspective on sound.
At Hoang Bao Khoa, the Neumann Studio is designed to allow customers to experience Neumann equipment directly in a studio environment, providing an opportunity to gain a deeper understanding of how the equipment reproduces sound in real-world use.
Source: Neumann – How Does Frequency Response Relate to Sound?