How to Read and Interpret Frequency Response Charts

Frequency response charts are essential tools for understanding how speakers, subwoofers, and other audio equipment perform across different frequencies. To truly understand what a frequency response chart is telling you, it’s important to approach it with a critical eye and a solid understanding of its components. 

Below, we break down the key elements of frequency response charts and explain how to analyze them effectively.

What Is a Frequency Response Chart?

A frequency response chart visually represents how an audio device reproduces sound across a range of frequencies, typically measured in hertz (Hz). The chart plots frequency on the horizontal axis (x-axis) and sound pressure level (SPL) in decibels (dB) on the vertical axis (y-axis). It provides a snapshot of the tonal balance and accuracy of the device.

In the following chart, the SPL is marked in a vertical red line, the frequency is marked in a horizontal green line. At one particular point, the blue dot tells us at the frequency of 100 Hz there is an SPL level of 50dB.

The Quest for Perfection

Most speaker manufacturers, Arendal included, are trying to create a balanced frequency response. This would equate to a flat smooth line from low frequencies to high frequencies. A flat response ensures that no frequencies are emphasized or reduced across the audible range.

Measurements Mater

In the same way that a thermometer will only be accurate in the environment it is measuring, speaker measurements are highly dependent on how and where the measurements are conducted. 

Manufacturers that provide frequency response measurements will typically have measurements conducted in an anechoic chamber. This allows for true response measurements without interactions from the room. These will show a drop in the low end below 40Hz typical rooms will have an elevated response due to room gain.

In the remarkable age we live in, it has never been easier to take frequency response measurements. However, this is a double-edged sword and there has never been as much misinformation and misinterpretation readily available. Hobbyists and forum members will very rarely have the specialized environment for anechoic measurements.

There are ways to measure the frequency response of a speaker outside of anechoic chambers, but it involves careful setup, calibration, and knowledge. Not all the measurements found in forums and social media will have been conducted correctly.

Know What You Are Looking At

Nobel Prize-winning economist Ronald Coase is quoted saying, "Torture the data, and it will confess to anything.” Even accurate measurements can be presented in ways that mislead or obscure the truth.

The following graphs (not made correctly nor of Arendal speakers) are of the same measurements but visually give the illusion of a radically different story.

Each graph represents the same data and the same frequency range, but the scale of the SPL is significantly altered in the first graph to give the appearance of a flat response. You need the right scale to see how uneven the frequency response is. There is a difference of nearly 30dB between 150Hz and 250Hz. This is a massive change in volume which is not clearly visible in the first graph.

Be sure you pay particular attention to the "homemade" frequency responses to make sure nothing is being done to doctor the data

Conclusion

Reading frequency response charts is an essential skill for evaluating audio equipment. By understanding the key elements of these charts and approaching them with a critical mindset, you can better match your gear to your preferences and achieve an optimal listening experience.