Here we present a portion of a chapter in the new book “The Audio Expert” by Ethan Winer, published by Focal Press.

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“Science is not a democracy that can be voted on with the popular opinion.” — Earl R. Geddes, audio researcher

In this chapter I explain how to assess the fidelity of audio devices and address what can and cannot be measured. Obviously, there’s no metric for personal preference, such as intentional coloration from equalization choices or the amount of artificial reverb added to recordings as an effect. Nor can we measure the quality of a musical composition or performance.

While it’s easy to tell—by ear or with a frequency meter—if a singer is out of tune, we can’t simply proclaim such a performance to be bad. Musicians sometimes slide into notes from a higher or lower pitch, and some musical styles intentionally take liberties with intonation for artistic effect.

So while you may not be able to “measure” Beethoven’s Symphony #5 to learn why many people enjoy hearing it performed, you can absolutely measure and assess the fidelity of audio equipment used to play a recording of that symphony. The science of audio and the art of music are not in opposition, nor are they mutually exclusive.

High Fidelity Defined

By definition, “high fidelity” means the faithfulness of a copy to its source. However, some types of audio degradation can sound pleasing—hence the popularity of analog tape recorders, gear containing tubes and transformers, and vinyl records. As with assessing the quality of music or a performance, a preference for intentional audio degradation cannot be quantified in absolute terms, so I won’t even try. All I can do is explain and demonstrate the coloration added by various types of audio gear and let you decide if you like the effect or not.

Indeed, the same coloration that’s pleasing to many people for one type of music may be deemed unacceptable for others. For example, the production goal for most classical (and jazz or big band) music is to capture and reproduce the original performance as cleanly and accurately as possible. But many types of rock and pop music benefit from intentional distortion ranging from subtle to extreme.

“The Allnic Audio’s bottom end was deep, but its definition and rhythmic snap were a bit looser than the others. However, the bass sustain, where the instrumental textures reside, was very, very good. The Parasound seemed to have a ‘crispy’ lift in the top octaves. The Ypsilon’s sound was even more transparent, silky, and airy, with a decay that seemed to intoxicatingly hang in the air before effervescing and fading out.” — Michael Fremer, comparing phonograph preamplifiers in the March 2011 issue of Stereophile magazine

Perusing the popular hi-fi press, you might conclude that the above review excerpt presents a reasonable way to assess and describe the quality of audio equipment. It is not. Such flowery prose might be fun to read, but it’s totally meaningless because none of those adjectives can be defined in a way that means the same thing to everyone. What is rhythmic snap? What is a “crispy” lift? And how does sound hang in the air and effervesce?

In truth, only four parameters are needed to define everything that affects the fidelity of audio equipment: noise, frequency response, distortion, and time-based errors. Note that these are really parameter categories that each contain several subsets. Let’s look at these categories in turn.