The direction of the headphone market used to be dictated by engineers with acoustical design expertise. But with Bluetooth headphones and earphones having taken over the mass market -- and all of them having at least a Bluetooth receiver and an internal amplifier, and likely a digital signal processor, too -- the chips inside the headphones now have at least as big an influence on the products as acoustical or even industrial design does. And the leader in those chips is Qualcomm -- partly because it owns the aptX audio codec, which audio enthusiasts consider de rigueur for any high-quality Bluetooth audio product.
When we’re in the midst of a global calamity, it seems like the duty of every columnist to comment on it. As an audio writer, I can claim no special insight into COVID-19 or the economic effects it will have, but this episode did make me think back to the last economic crisis -- in 2008, the year I began my freelance writing career. When it comes to headphones, the technology of that era -- only 12 years ago -- now seems as primitive as the automotive technology of 100 years ago.
Through the last several years, much discussion of headphone voicing -- how their designers tune the relative levels of the different audiobands to achieve their desired sound -- has centered around the Harman curve, the “target curve” shown to be preferred by most listeners. While the Harman curve is backed by the most extensive research ever done into headphone voicing, it’s still a long way from being a universally accepted standard, even among Harman’s own headphone brands. So we thought we’d ask some of today’s leading designers how they voice their headphones -- i.e., what their target curve is, how they arrived at that curve, and any other thoughts they might have on the subject.
Fresh into a new year and a new decade, worn out from trips to the 2020 Las Vegas International CES and the 2020 NAMM Show in Anaheim, California, I write this column filled with anticipation . . . and dread. Anticipation because I’m excited to see what new headphone innovations will appear this year and into the 2020s. Dread because I’m wondering how I’m going to test them.
Of the more than 100 new audio products that pass through my home every year, few stay longer than a couple of months. But after I tested a sample of the AKG K371 headphones borrowed from another reviewer, I immediately ordered a set from Amazon. Not only do they sound great; they’re a superb reference for any reviewer or headphone enthusiast. More than probably any other headphones available today, they tell us what sound most listeners like. The K371s’ response closely matches the Harman curve, developed by running hundreds of headphones past hundreds of listeners in blind tests to find out what kind of sound most listeners prefer.
It’s hard for me to believe it’s been seven years since researchers from Harman International presented the landmark paper “The Relationship between Perception and Measurement of Headphone Sound Quality” at the 2012 Audio Engineering Society Convention in San Francisco -- the first paper in which the company presented what became known as the “Harman curve,” the target frequency response that average listeners would like best. When I first read that paper, I assumed it would quickly revolutionize the headphone business. As a headphone reviewer, I knew that the various headphones and earphones then on the market often exhibited wildly different sounds -- even among different models in a company’s line -- which indicated that knowledge was lacking or simply being ignored.