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Magical Mystery Spec: Why Is Distortion Overlooked In Loudspeakers?

The sooner we understand distortion, the sooner improvements in performance can be made

Almost everybody in the pro audio business is a specification or “spec” junkie. From folks on the recording side to the sound reinforcement practitioners, we all want every detail of the technical performance of every piece of equipment in a system.

Specs seem extremely important, particularly those that represent a numerical improvement from past products, which are heralded as an advantage.

But man cannot live by specs alone. Quite often, those who turn to specifications to answer questions should instead be using their ears for the answer. You see, specs are all too often taken at face value, whether they’re actually relevant or not.

Manufacturers sometimes take advantage of this propensity to over-emphasize specs (and who can really blame them?) but sometimes it comes at the expense of real performance and value. Why is this phenomenon so prevalent in our industry?

The most straightforward answer is that it’s a by-product of a craft that has a highly subjective final product. It would be nice if we could judge the performance of the work via strictly objective measurement. But it’s not that easy. Therefore, the next best thing for sound professionals to do is point at the specs of as a validation of choices, system designs and configurations, and mixes.

No audio equipment spec is more revered than distortion. (O.K., a bit dramatic, but work with me.) Distortion is measured to two and sometimes three decimal points on almost every piece of equipment in the signal chain. From the input of the console to the output of the amplifier, every fraction of a percent of distortion is stressed.

Sure, this makes some sense from the standpoint that the sum of distortion throughout a signal chain can add up to something that could be easily heard and perhaps detrimental to audio quality.

But here’s the key question: What audio products do we rarely see distortion specs for? Transducers! Yes, somehow microphones and loudspeakers slip right under the distortion radar.

In many cases, I suspect that those who design and produce these products never even measure distortion. Leading to our next question: why? My best guess is that distortion measurements are omitted because they would be shockingly “substandard,” to put it kindly.

Mics are the first “acquisition point” for what is fed to a sound system. These electromechanical devices convert acoustic energy into electrical energy. We’re starting to see some digital mic concepts emerge, and some of these offer designs with the potential to lower distortion and therefore improve accuracy.

That said, I believe that distortion in mics is fundamentally different than distortion in loudspeakers. Mic distortion is part of the acoustic signature (or “sound”) of the device, which can be an important part of the creative process.

For example, a mic can “color” a source sound in a highly pleasing way, and very importantly, this applies only to that particular source, leaving the rest of the mix unaffected.

Therefore, I tend to think that any distortion spec for a given mic would not be all that critical in telling us much that is meaningful about its performance. Further, this “data” likely would be very hard to qualify.

Not Talking Fractions

Loudspeakers, however, are a whole different ballgame. The measured distortion produced by many loudspeakers is quite high indeed – we’re not talking fractions of a percent, rather, figures in the high single digits and even double digits.

Simply, this is a huge number compared to the total sum of electronic distortion that is created through the signal chain in a typical system, and perhaps most significantly, it applies to all output, not a single source.

In other words, loudspeaker distortion colors the entire mix. And it is even more detrimental because the distortion can wildly vary at different points throughout the coverage area of the loudspeaker. Further, it can vary throughout the bandwidth of the device.

As an industry – collectively – we’ve never demanded that manufacturers provide distortion specs on loudspeakers for comparative purposes. In addition, no manufacturer has ever made distortion the cornerstone of a marketing campaign.

To do this would require pointing out the fact that loudspeakers are, by their very nature, relatively high distortion devices, in turn prompting the need for real education on why a distortion spec matters, and also, why lower is better. The only realistic way that distortion in loudspeakers can be addressed: publish the specs and then work to improve on them.

Therefore it might be time, as an industry, for us to start to paying much closer attention to the concept of distortion in transducers, and specifically, loudspeakers. The sooner we can begin to understand typical distortion in these devices and its effect on our work, the sooner improvements in performance can be made that can result in better sound!

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