Frequency response graphs (or charts) are produced by testing audio products in recording studios. Headphones or speakers are placed on a common recording apparatus, frequencies are played through the product and the resulting sounds produced by the headphone or speaker are recorded and plotted on a graph. These graphs plot the volume, in decibels (dB), at which each frequency was reproduced.
In theory, a flat line from left to right on this graph would demonstrate that the headphone is able to reproduce all frequencies with the same strength and clarity. This is known as a flat response, which means the headphones are capable of reproducing audio exactly as a recording artist intended it to be heard. Most audiophile grade headphones, including RHA’s, aspire to get as close to this scenario as possible. Recently, however, a number of brands have taken a different approach to reproducing different frequencies, propagating the idea that an increased bass response means an increase in quality. The contrasting argument to this theory is that the balanced sound of a flat response headphone not only offers greater clarity and a better listening experience, especially when used for extended sessions, but also shows a greater degree of respect for the source audio.
Whilst being able to read a frequency chart will not allow you to accurately choose the better overall sounding headphone, it will allow you to get a rough idea of what that headphone/audio product is capable of achieving. The graph above is structured as a typical frequency response diagram, with frequency plotted along the X axis at the bottom. This axis shows the deep bass frequencies plotted on the far left, through to the top trebles on the right, displayed in Hertz (Hz). The variable of the graph is the volume (dB) represented on the Y axis. Three curves have been plotted on the graph, each representing the frequency response recording of a fictional audio product.
To begin with, consider Curve C. The curve shows that the product was able to produce bass frequencies with great fortitude, but gradually the volume at which it can reproduce sound gradually decrease as the frequency increases. In contrast, Curve B shows the response of a product which is able to produce very little bass, but much more in the upper end of the audible spectrum. When comparing the two, it’s easy to see that Curve B would not be ideal for bass-heavy dubstep or hip-hop music, and that Curve C wouldn’t be particularly suitable for acoustic music or spoken word recordings like audiobooks (unless the narrator happened to be James Earl Jones). However it should also be noted, that both curves have been heavily exaggerated for the purpose of this article. In reality, the chances of an audio product with such a response appealing to anybody’s tastes are very low.
Curve A has also been exaggerated, as it represents the ideal frequency response mentioned above - a completely flat response, showing the product is able to accurately reproduce every frequency in the audio spectrum. It’s almost impossible for consumer audio products to replicate this curve, though in the pursuit of the highest quality audio, RHA and other audio manufacturers who believe that natural, clear sound reproduction is ideal will continue to make products which get as close to this as possible.
Hopefully you now have a better understanding frequency graphs and you’ll stand a better chance of choosing an audio product which is perfect for you.