Overview of the Problem
Audio enthusiasts often spend dozens of hours tweaking equalizer (EQ) curves for each pair of headphones. The process can feel endless because every listener claims a different ideal balance of bass, midrange and treble. While many manufacturers ship headphones with a generic sound signature, the industry has long sought a scientific baseline that can serve as a starting point for all users. Recent research from former Harman engineer Sean Olive offers a practical shortcut: focus on two broad tone controls instead of sculpting a full‑frequency curve.
The Harman Target Study
Harman International conducted a large‑scale listening test that remains a cornerstone of headphone research. In the study, 249 participants used the same over‑ear headphones and adjusted only two parameters – bass and treble – to their liking. The middle 90 percent of users chose bass boosts ranging from +0.8 dB to +12.6 dB, a spread of nearly 12 dB. This wide variation initially suggested that highly personalized EQ would be necessary for each listener.
However, the same dataset showed that the central 50 percent of preferences clustered within a much narrower band around the so‑called Harman 2018 over‑ear target. That target represents an average frequency response derived from thousands of measurements and is widely used as a reference for “neutral” sound.
Sean Olive’s Key Findings
After 32 years at Harman, Sean Olive revisited the listener data in September 2023. His analysis confirmed that a modest adjustment range around the Harman 2018 target satisfies the preferences of half the tested population. Extending the range to cover the central 90 percent requires a dramatically larger boost or cut, which quickly becomes impractical for most users.
Olive emphasized that “a single target remains a useful population reference.” He clarified that the older +6.4 dB average from the 2015 study should not be added on top of the newer target. The 2015 figure was based on a different loudspeaker‑in‑room baseline, whereas the 2018 target already incorporates more recent measurements.
Another double‑blind comparison, also performed by Harman, showed that a headphone tuned to the Harman target received the highest average rating among three commercial models and was preferred by 60.1 percent of listeners across four countries. This reinforces the idea that a population‑level reference is a solid starting point, even if it does not capture every individual nuance.
Practical EQ Workflow Using AutoEq and Oratory1990 Presets
The most efficient way to apply Olive’s insight is to begin with a model‑specific correction that aligns the headphone’s measured response to the Harman 2018 target. Tools such as AutoEq can import a headphone’s measured frequency response, generate a set of corrective filters, and output a preset file for popular EQ apps. The open‑source project maintained by the community engineer known as oratory1990 provides ready‑made presets for hundreds of models, each already tuned toward the Harman reference.
Once the corrective filters are in place, the user should leave them untouched. The next step is to adjust the two broad shelves that AutoEq includes by default: a low‑frequency shelf centered at 105 Hz for bass and a high‑frequency shelf at 10 kHz for treble. Some model‑specific presets, such as the one for the Austrian Audio The Composer, move the treble shelf to 2.5 kHz, reflecting the designer’s assessment of the headphone’s natural roll‑off.
Listeners can then raise or lower each shelf until the overall balance feels comfortable. Because the underlying correction already places the response near the Harman target, only modest adjustments are needed to satisfy most personal tastes.
Why Two Broad Shelves Capture Most Variations
Olive’s research showed that the four listener clusters identified in the original study were unstable – changing the clustering algorithm or scaling the data altered the groupings. This suggests that listeners do not fall into fixed “type A” or “type B” categories that require separate EQ curves. Instead, the primary source of variation appears to be overall bass and treble preference, which can be addressed with the two shelves.
Additional work by Davy (oratory1990) measured sound pressure at the ear‑canal entrance for 15 individuals wearing the same headphones. The results confirmed that physical differences in ear shape and fit cause measurable low‑frequency variation, especially in closed‑back designs. Davy noted that closed‑back models often need extra adjustment in the 2–4 kHz region as well as in the low end. Olive argued that a simple bass and treble filter can likely accommodate most of these reported individual variations, though he qualified the claim as a hypothesis rather than a proven outcome.
Limitations and Areas for Future Research
While the two‑shelf approach works for a large portion of listeners, it does not capture every nuance. Olive’s presentation did not test how the same headphones interact with different ear shapes, nor did it evaluate spatial fidelity or the impact of headphone resonance peaks that fall outside the broad shelf frequencies. Moreover, the four commercial headphones used in the predictive‑power test differed in midrange response and resonances, factors that broad tone controls cannot fully address.
Future studies could combine precise ear‑canal measurements with personalized EQ algorithms that adjust not only bass and treble but also midrange peaks. Machine‑learning models trained on large datasets of listener preferences and headphone measurements might eventually predict a more detailed curve for each individual, but until such tools become reliable, Olive’s recommendation remains the most time‑efficient method.
Conclusion: A Simple Path to Better Sound
Sean Olive’s analysis distills decades of listener research into a single actionable tip: start with a Harman‑target correction, keep the corrective filters intact, and fine‑tune only the broad bass and treble shelves. This workflow captures the preferences of the central 50 percent of listeners while avoiding the overwhelming complexity of full‑spectrum EQ. For most users, the result is a balanced, enjoyable sound without the need for hours of trial and error.