There was something special that happened when we introduced the AKG K371 headphones and then later the K371-BT headphones: they were the first headphones to be tuned to the AKG Reference Response Acoustics Curve. Before we get too deep into that, we should probably explain what we mean by “tuned to a curve.”
Most listening devices, whether they’re headphones or speakers, are designed with the goal of reproducing sound with certain frequency characteristics. To achieve that goal, headphone and speaker manufacturers create a frequency response curve that represents those desired tonal qualities, and then engineer their products to attempt to match the curve. Until now, these characteristics have often been arbitrary decisions made by product engineers to make the product sound a certain way or they were tailored to customer preferences (which explains the hyped bass and treble found in consumer products).
In the professional realm, hyped or artificially accentuated frequencies are not desirable. In order to make accurate mix or editing decisions, it’s best to hear things as they are in their natural state without colorization. That means your listening devices should have as flat or neutral a frequency response as possible. Many audiophiles also find this a desirable quality because it means that you will enjoy the music the way artists, recording engineers and producers intended.
Tuning speakers and studio monitors to be neutral (when measured by acoustic testing instrumentation) is the way to go. But over the years, here at AKG, we’ve discovered that tuning headphones to be absolutely neutral presents a problem: they just don’t sound right to listeners. You may be wondering why. It turns out that it has to do with the way the human ear processes incoming sound. Our ears evolved to hear sound most accurately in the direction that your head is facing. Speakers are most commonly placed in front of a listener, so if they are neutrally tuned they will be heard as such. When you turn a speaker (and that is essentially what headphones are, tiny speakers) and point it directly into the ear from the side, the geometry of your ear reflects the sound differently than if the sound is coming in head on, and that colors how you perceive the sound.
This presents a real dilemma for professional headphone development: a scientifically neutral representation of a sound doesn’t sound “neutral” when heard through headphones. We decided to solve the problem and embarked on an exhaustive, five-year study on how the human brain perceives sonic neutrality that involved hundreds of subjects, consisting of a wide range of ages and demographics. The result was the HARMAN Target Curve, which when applied to headphones became the AKG Reference Response Acoustics Curve.
As we mentioned above, AKG K371 and K371-BT headphones are the first headphones to be engineered to match the AKG Reference Response Acoustics Curve. But we didn’t stop at just the tuning, we wanted to introduce a truly revolutionary listening experience. With that in mind, we designed new largest-in-class 50mm, high-performance, titanium-coated drivers with pure oxygen-free, copper voice coils, and placed them in closed-back, oval earcups.
The oval earcups are another interesting innovation for AKG headphones. You may have noticed that most of our other models have that traditional circular design, but what shape are your ears? They are much closer to ovals than circles. And if you reach below your ear, right where your skull meets your jawbone, you’ll notice a gap there….gaps mean leakage, and as a result with circular headphones, where the gap is more pronounced, you experience some loss of low frequency performance.
So when you combine together large, titanium-coated drivers, tuned to the AKG Reference Response Acoustics Curve, in a closed-back, oval design, with slow retention foam earpads (which further improve the isolation), in the AKG K371 and K371-BT, you not only get headphones that sound neutral, the way your ears intended, but you also get headphones that sound amazing that also feature an unprecedented frequency range of 5Hz to 40kHz.
We could go on and on about how happy we are with the K371 and K371-BT headphones, but we started this blog intending to speak about the AKG Reference Response Acoustics Curve. Recently, radio and TV presenter and journalist (KCRW, KCSN, MTV), Nic Harcourt, sat down with HARMAN’s Senior Fellow of Acoustical Research, Dr. Sean Olive, and Senior Engineer, Omid Khonsaripour, to discuss how the AKG Reference Response Acoustics Curve came to be and why it matters. Check out the video below to hear the full story about the curve from the people who created it.